What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> At the present time, the information contained in a roentgenogram can be extracted only by a radiologist observing it. That this link can sometimes fail has recently been emphasized by Tuddenham (1) and Garland (2), who have reported frequent perceptual errors by radiologists viewing roentgenograms demonstrating fairly obvious lesions. Such errors have also been shown by Zeidner and Sadacca (3) and Enoch (4) in their studies of photointerpreters reading aerial photographs. There are two stages in the visual perception of detail. First, the object must be focused upon the fovea; second, this focused image must be translated into meaning by the observer's brain. The fovea subtends an angle of only 2°, so that at 30 inches the area of distinct vision is a circle about 1 inch in diameter. Thus, some 300 separate eye fixations are necessary to cover the area presented by a 14 × 17-inch roentgenogram at this distance. The eye searches the film by moving in small rapid jumps of high velocity (saccadic movements)... <s> BIB001 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Eye movements of 24 subjects, including untrained laymen, medical students, radiology residents, and staff radiologists, were recorded while the subjects viewed normal and abnonnal chest radiographs. Evolution of search patterns from the localized central pattern of the untrained observer to the circumferential pattern of the radiologist is discussed. It is postulated that development of the pattern is secondary to development of knowledge about the location and characteristic features of normal and abnormal. Improvement in search patterns comes about as a result of concentrating on clearly defining the abnormal feature that is the object of search and the normal background that envelops it. <s> BIB002 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> There has been much recent work on foraging that derives hypotheses from the assumption that animals are in some way optimizing in their foraging activities. Useful reviews may be found in Krebs (1973) or Schoener (1971). The problems considered usually relate to breadth of diet (Schoener, 1969, 1971; Emlen 1966; MacArthur, 1972; MacArthur and Painka, 1966; Marten, 1973; Pulliam, 1974; Werner, 1974; Werner and Hall, 1974; Timmins, 1973; Pearson, 1974; Rapport, 1971; Charnov, 1973,1976; Eggers, 1975), strategies of movement (Cody, 1971; Pyke, 1974; Smith, 1974a, b; Ware, 1975), or use of a patchy environment (Royama, 1970; MacArthur and Pianka, 1966; Pulliam, 1974; Smith and Dawkins, 1971; Tullock, 1970; Emlen, 1973; Krebs, 1973; Krebs, Ryan, and Charnov, 1974; Charnov, Orians, and Hyatt, 1976). The above list of references is provided as a beginning to this fast expanding literature and is far from exhaustive. This paper will develop a model for the use of a “patchy habitat” by an optimal predator. The general problem may be stated as fohows. Food is found in clumps or patches. The predator encounters food items within a patch but spends time in traveling between patches. This is schematically shown in Fig. 1. The predator must make decisions as to which patch types it will visit and when it will leave the patch it is presently in. This paper will focus on the second question. An important assumption of the model is that while the predator is in a patch, its food intake rate for that patch decreases with time spent there. The predator depresses (Charnov, Orians, and Hyatt, 1976) the availability of food to itself so that the amount of food gained for T time spent in a patch of type i is hi(T), where the function rises to an asymptote. A hypothetical example is shown in Fig. 2. While it is not necessary that the first derivative of hi(T) be decreasing for all T (it might be increasing at first if the predator scares up prey upon arrival in a new patch), I will limit discussion to this case since more <s> BIB003 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Eye movements were recorded while four subjects searched a set of 60 films, 24 normal and 36 abnormal, for pulmonary nodules. Error rates, scanning patterns and the dwell time of fixation clusters on normal and nodule-containing areas of the film were studied. Using the assumption that prolonged dwe <s> BIB004 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> A new hypothesis about the role of focused attention is proposed. The feature-integration theory of attention suggests that attention must be directed serially to each stimulus in a display whenever conjunctions of more than one separable feature are needed to characterize or distinguish the possible objects presented. A number of predictions were tested in a variety of paradigms including visual search, texture segregation, identification and localization, and using both separable dimensions (shape and color) and local elements or parts of figures (lines, curves, etc. in letters) as the features to be integrated into complex wholes. The results were in general consistent with the hypothesis. They offer a new set of criteria for distinguishing separable from integral features and a new rationale for predicting which tasks will show attention limits and which will not. <s> BIB005 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Harvard Medical School and Peter Bent Brigham Hospital, Boston, Massachusetts 02115 The model treats the detection of targets in a visual search task as a concatenation of two serial detection stages. Preattentive visual mechanisms in the initial stage function as a filter, selecting specific features of a visual pattern for the observer’s explicit attention and final cognitive evaluation. The model uses bivariate normal distributions to represent the decision variables for the two serial stages, assuming different parameters for the target and nontarget features in a test set. The model is applied to the detection performance of radiologists interpreting chest x-rays under various conditions of search. It accounts for the substantial improvement in radiologists’ ability to distinguish between target and nontarget test features when they had to search the x-ray images, compared to their performance without visual search. A change in the ROC curve between two different search tasks could be interpreted as a shift in the selection cutoff used by the preattentive filter. <s> BIB006 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> A group of 100 carefully selected chest radiographs was read by ten observers, five experienced and five inexperienced. The radiographs were chosen to present the readers with a disproportionately large number of both subtle abnormalities and nonpulmonary lesions. Each reader was allowed to search the radiographs for as long as appropriate, up to a maximum of four minutes. The length of time taken for each observation was recorded to the nearest second. The time-perception data were plotted on both linear and semilogarithmic graphs. The results showed that experienced readers concluded their visual search while positive detection rate was higher than the rate for false-positives. For lesions in the central phasic, with both a rapid and a slow component of perception. If these data are plotted on a semilogarithmic scale, each of the two components plots as a straight line. For lesions in the periphery of the radiograph (chest wall and upper abdomen), the time-perception curve is monophasic, showing only a slow component. <s> BIB007 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Having previously fixated a location increases the latency of subsequent saccadic eye movements towards that location. In a saccadic pursult task, the last saccade of each trial was directed directly at, or up to three deg away from the location of a previous fixation on that trial. Saccades to a previously fixated location were longer by 8 to 15 msec than those directed 3 deg away from any previously fixated location, even 1700 msec after the prior fixation. The elevation in saccade latency is consistent with an attentional bias in favor of fresh sources of information. <s> BIB008 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The contrast sensitivity of the retina is greatest in the center and decreases rapidly toward the periphery. Therefore, the detection of low-contrast lung nodules depends upon the manner in which the image is sampled by retinal receptors as eye fixations jump across the image during scanning. The scanning performance of two radiologists was compared with two computed models, a systematic and a random scanner. Although radiologists do not seem to have random scanning patterns, their coverage of the image was matched more closely by the random model. This suggests that radiologists employ a scanning strategy that is designed to cover the image of the lungs in a minimum time using the smallest possible visual field. The visual field size that is most effective in detecting nodules during search has a radius of 3.5 degrees visual angle. Nodule detection may be limited by basic neurologic constraints on human scanning performance. <s> BIB009 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Observers with four different levels of radiological experience performed a recognition memory task on slides of faces and chest X-ray films. Half of the X-ray films revealed clinically significant abnormalities and half did not. Recognition memory for faces was uniformly high across all levels of radiological experience. Memory for abnormal X-ray films increased with radiological experience and, for the most experienced radiologists, was equivalent to memory for faces. Surprisingly, recognition memory for normal films actually decreased with radiological experience from above chance to a chance level. These results indicate that radiological expertise is associated with selective processing of clinically relevant abnormalities in X-ray images. Expert radiologists appear to process X-ray images the way that we all process faces, by quickly detecting and devoting processing resources to features that distinguish one stimulus from another. However, the selective processing of X-ray films appears to be restricted to clinically relevant abnormalities. As they develop the ability to detect these abnormalities, radiologists appear to lose the ability to detect variations in normal features. <s> BIB010 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> “Satisfaction of search” (SOS) refers to the effect in which a second lesion remains undetected after detection of another lesion on the same radiograph. The objective of this study was to clarify our understanding of SOS by relating it to total time of inspection and time intervals before, between, and after discovery of lesions. Detection accuracy of native lesions in chest radiographs, before and after the addition of a simulated nodular lesion, was measured for ten observers. Analysis of data from this and a previous experiment showed that average perceptual accuracy of individual receiver operating characteristic curves was significantly reduced with the addition of the nodules. Plots and analyses of search time revealed that, on average, during a typical 46-second inspection of a case, simulated nodules were found at 18 seconds, native abnormalities at 25 seconds, and false positives occurred at 33 seconds. Time needed to find nodules did not depend on whether native lesions were present; time to find native lesions did not change with addition of nodules; and total search time was the same for images with one, two, or no lesions. The detection results show that the SOS effect was obtained, but that interrupting search in order to measure it also diminishes accuracy. Analysis of the time course data relates SOS to perceptual capture and strategic halting of search. <s> BIB011 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The very limited capacity of short-term or working memory is one of the most prominent features of human cognition. Most studies have stressed delimiting the upper bounds of this memory in memorization tasks rather than the performance of everyday tasks. We designed a series of experiments to test the use of short-term memory in the course of a natural hand-eye task where subjects have the freedom to choose their own task parameters. In this case subjects choose not to operate at the maximum capacity of short-term memory but instead seek to minimize its use. In particular, reducing the instantaneous memory required to perform the task can be done by serializing the task with eye movements. These eye movements allow subjects to postpone the gathering of task-relevant information until just before it is required. The reluctance to use short-term memory can be explained if such memory is expensive to use with respect to the cost of the serializing strategy. <s> BIB012 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> RATIONALE AND OBJECTIVES ::: The authors investigated how training and experience affect the performance of observers searching mammograms for breast masses. ::: ::: ::: METHODS ::: Eye positions of mammographers, mammography technologists, mammography residents, and laypersons were compared to scan paths generated by a simulated scanner as each searched nine two-view digital mammogram pairs for breast masses. ::: ::: ::: RESULTS ::: Analysis of time-to-hit data revealed that mammographers and mammography technologists with the most extensive training and experience had the fastest search times in the detection and confirmation of a breast mass on two views. Scanning patterns of less-experienced mammography residents were less efficient due to wider dispersion of visual attention between potential breast masses and perturbations in breast parenchyma. Because laypersons lacked both training and experience in mammography, bright blobs in the breast image were considered to be intuitively valid target candidates and these features distracted the search by capturing visual attention. ::: ::: ::: CONCLUSION ::: Experience reading normal and abnormal mammograms plays a critical role in training radiologists. Experience combined with training provides the basis for generating efficient visual search strategies and developing distinctive conceptual criteria for perceptual differentiation and interpretation of true breast masses from image artifacts and structured noise that mimics breast abnormalities. <s> BIB013 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Abstract The pattern of interactions between visual search profile (serial versus nonserial) and perceptual organization type (functionally local versus global) was investigated in three experiments. The task was a matching judgment performed on two separate figures that fit in a jigsaw-puzzle fashion. Reaction times and errors showed that serial search preferably goes together with local organization and nonserial search with global organization. Choice of search profile and organization type depend on task and individual preference. Structural complexity in the target area reinforces the combination of local organization and serial search. This combination was also chosen by subjects preferring accuracy. The combination of global organization and nonserial search was chosen with simpler targets or by subjects preferring speed. The results support an interactive notion of perceptual organization and search. Perceptual organization type is determined by individual preferences in combination with visual search task demands; visual search is guided by the specific organization of the stimulus pattern. <s> BIB014 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Rationale and Objectives. The goal of this study was to determine if radiologists possess superior visual search and analysis skills compared with those of laypeople. Materials and Methods. In two experiments, radiologists and laypeople searched one of two complex pictorial scenes for hidden targets. Eye position was recorded during the search. Two measures of performance were obtained: accuracy of detecting targets as measured by using alternative free response receiver operating characteristic analysis and visual search efficiency as measured by using eye position analysis. Results. There were no statistically significant differences in detection performance between radiologists and laypeople for either of the search tasks. Radiologists took longer on average to search the images and to first fixate on the targets than did the laypeople. For both groups, true-positive and false-positive decisions were associated with longer dwell times than true-negative decisions. As with radiology search tasks, false-negative decisions were also associated with longer dwell times than true-negative decisions. Conclusion. Performance on two visual search and detection tasks indicate that radiologists do not possess superior visual skills compared with laypeople. Radiology expertise is more likely to be a combination of specific visual and cognitive skills derived from medical training and experience in detecting and determining the diagnostic importance of radiographic findings. <s> BIB015 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Humans spend a lot of time searching for things, such as roadside traffic signs1, soccer balls2 or tumours in mammograms3. These tasks involve the deployment of attention from one item in the visual field to the next. Common sense suggests that rejected items should be noted in some fashion so that effort is not expended in re-examining items that have been attended to and rejected. However, common sense is wrong. Here we asked human observers to search for a letter ‘T’ among letters ‘L’. This search demandsvisual attention and normally proceeds at a rate of 20–30 milliseconds per item4. In the critical condition, we randomly relocated all letters every 111 milliseconds. This made it impossible for the subjects to keep track of the progress of the search. Nevertheless, the efficiency of the search was unchanged. Theories of visual search all assume that search relies on accumulating information about the identity of objects over time5,6,7. Such theories predict that search efficiency will be drastically reduced if the scene is continually shuffled while the observer is trying to search through it. As we show that efficiency is not impaired, the standard theories must be revised. <s> BIB016 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> RATIONALE AND OBJECTIVES ::: The authors evaluated the influence of perceptual and cognitive skills in mammography detection and interpretation by testing three groups representing different levels of mammography expertise in terms of experience, training, and talent with a mammography screening-diagnostic task. ::: ::: ::: MATERIALS AND METHODS ::: One hundred fifty mammograms, composed of unilateral cranial-caudal and mediolateral oblique views, were displayed in pairs on a digital workstation to 19 radiology residents, three experienced mammographers, and nine mammography technologists. One-third of the mammograms showed malignant lesions; two-thirds were malignancy-free. Observers interacted with the display to indicate whether each image contained no malignant lesions or suspicious lesions indicating malignancy. Decision time was measured as the lesions were localized, classified, and rated for decision confidence. ::: ::: ::: RESULTS ::: Compared with performance of experts, alternative free response operating characteristic performance for residents was significantly lower and equivalent to that of technologists. Analysis of overall performance showed that, as level of expertise decreased, false-positive results exerted a greater effect on overall decision accuracy over the time course of image perception. This defines the decision speed-accuracy relationship that characterizes mammography expertise. ::: ::: ::: CONCLUSION ::: Differences in resident performance resulted primarily from lack of perceptual-learning experience during mammography training, which limited object recognition skills and made it difficult to determine differences between malignant lesions, benign lesions, and normal image perturbations. A proposed solution is systematic mentor-guided training that links image perception to feedback about the reasons underlying decision making. <s> BIB017 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Abstract Eye position was recorded in different viewing conditions to assess whether the temporal and spatial characteristics of saccadic eye movements in different individuals are idiosyncratic. Our aim was to determine the degree to which oculomotor control is based on endogenous factors. A total of 15 naive subjects viewed five visual environments: (1) The absence of visual stimulation (i.e. a dark room); (2) a repetitive visual environment (i.e. simple textured patterns); (3) a complex natural scene; (4) a visual search task; and (5) reading text. Although differences in visual environment had significant effects on eye movements, idiosyncrasies were also apparent. For example, the mean fixation duration and size of an individual’s saccadic eye movements when passively viewing a complex natural scene covaried significantly with those same parameters in the absence of visual stimulation and in a repetitive visual environment. In contrast, an individual’s spatio-temporal characteristics of eye movements during active tasks such as reading text or visual search covaried together, but did not correlate with the pattern of eye movements detected when viewing a natural scene, simple patterns or in the dark. These idiosyncratic patterns of eye movements in normal viewing reveal an endogenous influence on oculomotor control. The independent covariance of eye movements during different visual tasks shows that saccadic eye movements during active tasks like reading or visual search differ from those engaged during the passive inspection of visual scenes. <s> BIB018 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Using overt orienting, participants searched a complex visual scene for a camouflaged target (Waldo from the “Where's Waldo?™” books). After several saccades, we presented an uncamouflaged probe (black disk) while removing or maintaining the scene, and participants were required to locate this probe by foveating it. Inhibition of return was observed as a relative increase in the time required to locate these probes when they were in the general region of a previous fixation, but only when the search array remained present. Perhaps also reflecting inhibition of return, preprobe saccades showed a strong directional bias away from a previously fixated region. Together with recent studies that replicate the finding of inhibition at distractor locations following serial but not parallel visual search—so long as the search array remains visible—these data strongly support the proposal that inhibition of return functions to facilitate visual search by inhibiting orienting to previously examined locations. <s> BIB019 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Abstract Global context plays an important, but poorly understood, role in visual tasks. This study demonstrates that a robust memory for visual context exists to guide spatial attention. Global context was operationalized as the spatial layout of objects in visual search displays. Half of the configurations were repeated across blocks throughout the entire session, and targets appeared within consistent locations in these arrays. Targets appearing in learned configurations were detected more quickly. This newly discovered form of search facilitation is termed contextual cueing. Contextual cueing is driven by incidentally learned associations between spatial configurations (context) and target locations. This benefit was obtained despite chance performance for recognizing the configurations, suggesting that the memory for context was implicit. The results show how implicit learning and memory of visual context can guide spatial attention towards task-relevant aspects of a scene. <s> BIB020 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Observers searched for a target among distractors while the display items traded places every 110 ms. Search was slower when the target was always relocated to a position previously occupied by a distractor than when the items remained in place, showing the importance of memory for locations in a visual search task. Experiment 2 repeated a previous study in which items could move to any location within the display, but used a larger range of set sizes than tested in the earlier study. A cost in search times to relocating items was found at the larger set sizes, most likely reflecting that the probability that the target would replace a distractor increased with the set size. The findings provide strong evidence for the role of memory for locations within trials in a visual search task. <s> BIB021 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Evidence is presented supporting the thesis that performance in visual search tasks is affected by the contribution of memory processes. Three levels of analysis, corresponding to the various time scales present in a typical search experiment, are discussed. Perceptual learning involves the task and stimulus specific improvement seen across blocks of training. Trial-to-trial priming has an influence which extends over 5-8 trials and lasts on the order of 30 s. Within-trial tagging prevents the re-inspection of already attended (or fixated) items. Also at the within-trial level of analysis, parallel accumulation of evidence for target presence/absence or target location inherently involves memory mechanisms. Organizing the various phenomena in this way makes it apparent that the various mechanisms may interact in a causal way. Within-trial tagging may contribute to priming which may contribute to perceptual learning. Recent proposals that visual search is memoryless (amnesic) are discussed and dismissed. <s> BIB022 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Klein (1988) reported thatinhibitory tagging (i.e., inhibition of return in visual search) made reaction times for the detection of small probes increase at locations where there had previously been rejected items in serial visual search. It is reasonable that the attended and rejected locations are inhibited. However, subsequent studies did not support Klein’s idea. In these studies, inhibitory tagging was tested after removing the items from the search tasks. The paradigms in these studies were not appropriate for testing an object-based inhibitory effect because the objects (i.e., items) were removed from the display. In the present study, we found that evidence of inhibitory tagging could be observed only when the items of the search tasks were maintained until the responses for the small probes were made. This appeared to be an object-based effect. <s> BIB023 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> A random scan is a quicker way to find items in a display than a systematic search.AbstractHow swiftly can the object of your attention be changed? Consider two ways to deploy attention: it can be commanded from place to place by a deliberate act of will, or it can run freely without specific instruction. Here we use a visual search task to show that deliberate movement of attention is significantly slower because of an internal limit on the speed of volitional commands. <s> BIB024 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> By monitoring subjects' eye movements during a visual search task, we examined the possibility that the mechanism responsible for guiding attention during visual search has no memory for which locations have already been examined. Subjects did reexamine some items during their search, but the pattern of revisitations did not fit the predictions of the memoryless search model. In addition, a large proportion of the refixations were directed at the target, suggesting that the revisitations were due to subjects' remembering which items had not been adequately identified. We also examined the patterns of fixations and compared them with the predictions of a memoryless search model. Subjects' fixation patterns showed an increasing hazard function, whereas the memoryless model predicts a flat function. Lastly, we found no evidence suggesting that fixations were guided by amnesic covert scans that scouted the environment for new items during fixations. Results do not support the claims of the memoryless search m... <s> BIB025 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Many experiments have shown that the human visual system makes extensive use of contextual information for facilitating object search in natural scenes. However, the question of how to formally model contextual influences is still open. On the basis of a Bayesian framework, the authors present an original approach of attentional guidance by global scene context. The model comprises 2 parallel pathways; one pathway computes local features (saliency) and the other computes global (scene-centered) features. The contextual guidance model of attention combines bottom-up saliency, scene context, and top-down mechanisms at an early stage of visual processing and predicts the image regions likely to be fixated by human observers performing natural search tasks in real-world scenes. <s> BIB026 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> OBJECTIVE ::: This article describes the time course of lesion detection on digital mammograms using data about both eye position and decision time to compare performance between experienced mammographers and trainees. Research indicates that a longer decision time works against performance in the interpretation of chest radiographs because the likelihood of error is increased, particularly for trainees. Is this relation between decision time and performance also true for interpreting mammograms? Is there an optimal decision time-performance trade-off for detecting breast lesions? ::: ::: ::: MATERIALS AND METHODS ::: Six radiology trainees (experience, 302-976 cases) and three mammographers (experience, 3000-5000 cases per year) reviewed 40 test cases. Each test case was represented by two mammograms that showed different views of the same breast. Twenty breasts contained suspicious lesions, and 20 were lesion-free. An interactive computer display system with an eye-head tracker measured the timing of decisions, where visual attention was directed, and how much time was spent fixating on a region of interest for each decision. Eye position was monitored during an initial-decision phase, and decision times were measured throughout a final-decision phase during which suspicious lesions recognized initially were interpreted and localized. Performance was analyzed using localization receiver operating characteristic curves. ::: ::: ::: RESULTS ::: The time course of interpreting mammograms is similar to that for interpreting chest radiographs. Mammographers detected 71% of the true lesions within 25 sec, and trainees detected 46% within 40 sec. Both a fixation dwell time of 1000 msec and a high level of confidence in the decision were associated with the detection of true lesions for the mammographers but not for the trainees. ::: ::: ::: CONCLUSION ::: Mammographers detected most breast lesions by global recognition within 25 sec, but trainees took more time. Prolonging one's search beyond the global recognition phase yielded few new lesions and increased the risk of error. <s> BIB027 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Four observer groups with different levels of expertise were tested in an investigation into the comparative nature of expert performance. The radiological task was the detection and localization of significant pulmonary nodules in postero-anterior vies of the chest in adults. Three test banks of 40 images were used. The observer groups were 6 experienced radiographers prior to a six month training program in chest image interpretation, the same radiographers after their tr4aining program, and 6 fresher undergraduate radiography students. Eye tracking was carried out on all observers to demonstrate differences in visual activity and nodule detection performance was measured with an AFROC technique. Detection performances of the four groups showed the radiologists and radiographers after training were measurably superior at the task. The eye-tracking parameters saccadic length, number of fixations visual coverage and scrutiny timer per film were measured for all subjects and compared. The missed nodules fixated and not fixated were also determined for the radiologist group. Results have shown distinct stylistic differences in the visual scanning strategies between the experienced and inexperienced observers that we believe can be generalized into a description of characteristics of expert versus non-expert performance. The findings will be used in the educational program of image interpretation for non-radiology practitioners. <s> BIB028 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Abstract How do we find a target item in a visual world filled with distractors? A quarter of a century ago, in her influential ‘Feature Integration Theory (FIT)', Treisman proposed a two-stage solution to the problem of visual search: a preattentive stage that could process a limited number of basic features in parallel and an attentive stage that could perform more complex acts of recognition, one object at a time. The theory posed a series of problems. What is the nature of that preattentive stage? How do serial and parallel processes interact? How does a search unfold over time? Recent work has shed new light on these issues. <s> BIB029 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Research has demonstrated that oculomotor visual search is guided by memory for which items or locations within a display have already been inspected. In the study reported here, we used a gaze-contingent search paradigm to examine properties of this memory. Data revealed a memory buffer for search history of three to four items. This buffer was effected in part by a space-based trace attached to a location independently of whether the object that had been seen at that position remained visible, and was subject to interference from other stimuli seen in the course of a trial. <s> BIB030 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> A test bank of verified chest radiographs was compiled for visual search experiments to investigate radiology performance in the detection of early lung cancer. A measure of the physical characteristics of the lesions was derived to determine the conspicuity (chi) of the nodules and to investigate possible causes of failed detection. Observer performance was measured by alternate free response operating characteristic (AFROC) methodology and was supplemented with visual search recording. Correlation of AFROC scores and the chi values was poor but inspection of the visual search recordings showed that most nodules were fixated. Fixations on missed lesions produced average dwell times greater than three times the minimum duration thought to be associated with detection. We conclude that the majority of errors were failures of decision rather than detection and comment on the implications of this for strategies to improve diagnostic effectiveness. <s> BIB031 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> We recorded oculomotor scanpaths in a task that required individuals to scan through displays consisting of a small number (between 3 and 12) of near-identical items. The task required each item to be fixated at least once and our objective was to explore the principles governing the generation of scanpaths. In general the observers carried out the task efficiently, although omissions occurred quite frequently (about 25% of trials) in the 12-item case. Backtracking occurred rarely except in the case of immediate rescanning back to the previously fixated item. Such immediate backtracking occurred on about 4% of fixations and, in contrast to more distant backtracking, was not associated with increased errors. Evidence was found for both directional (raster-like) scanning strategies and scanning strategies based on the global external contour. <s> BIB032 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> We present evidence that scan paths in visual search can include a systematic component. The task for subjects in the experiment was to search for a target that was either present or absent. With regular grid-like displays, participants generated more horizontal saccades than vertical saccades. Disruption of the grid structure in the display modulated but did not eliminate the systematic component. This is consistent with the scan path being partly determined by a cognitive strategy. We discuss the implications of this finding for studies that use refixation to investigate memory mechanisms in visual search. <s> BIB033 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The eye movements of native English speakers, native Chinese speakers, and bilingual Chinese/English speakers who were either born in China (and moved to the US at an early age) or in the US were recorded during six tasks: (1) reading, (2) face processing, (3) scene perception, (4) visual search, (5) counting Chinese characters in a passage of text, and (6) visual search for Chinese characters. Across the different groups, there was a strong tendency for consistency in eye movement behavior; if fixation durations of a given viewer were long on one task, they tended to be long on other tasks (and the same tended to be true for saccade size). Some tasks, notably reading, did not conform to this pattern. Furthermore, experience with a given writing system had a large impact on fixation durations and saccade lengths. With respect to cultural differences, there was no evidence that Chinese participants spent more time looking at the background information (and, conversely less time looking at the foreground information) than the American participants. Also, Chinese participants’ fixations were more numerous and of shorter duration than those of their American counterparts while viewing faces and scenes, and counting Chinese characters in text. <s> BIB034 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Horowitz and Wolfe (1998, 2003) have challenged the view that serial visual search involves memory processes that keep track of already inspected locations. The present study used a search paradigm similar to Horowitz and Wolfe's (1998), comparing a standard static search condition with a dynamic condition in which display elements changed locations randomly every 111 ms. In addition to measuring search reaction times, observers' eye movements were recorded. For target-present trials, the search rates were near-identical in the two search conditions, replicating Horowitz and Wolfe's findings. However, the number of fixations and saccade amplitude were larger in the static than in the dynamic condition, whereas fixation duration and the latency of the first saccade were longer in the dynamic condition. These results indicate that an active, memory-guided search strategy was adopted in the static condition, and a passive “sit-and-wait” strategy in the dynamic condition. <s> BIB035 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Although there has been some controversy as to whether attention is guided by memory during visual search, recent findings have suggested that memory helps to prevent attention from needlessly reinspecting examined items. Until now, it has been assumed that some form of retrospective memory is responsible for keeping track of examined items and preventing revisitations. Alternatively, some form of prospective memory, such as strategic scanpath planning, could be responsible for guiding attention away from examined items. We used a new technique that allowed us to selectively prevent retrospective or prospective memory from contributing to search. We demonstrated that both retrospective and prospective memory guide attention during visual search. <s> BIB036 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Using a gaze-contingent paradigm, we directly measured observers’ memory capacity for fixated distractor locations during search. After approximately half of the search objects had been fixated, they were masked and a spatial probe appeared at either a previously fixated location or a non-fixated location; observers then rated their confidence that the target had appeared at the probed location. Observers were able to differentiate the 12 most recently fixated distractor locations from non-fixated locations, but analyses revealed that these locations were represented fairly coarsely. We conclude that there exists a high-capacity, but low-resolution, memory for a search path. <s> BIB037 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> It has been argued that visual search is a valid model for human foraging. However, the two tasks differ greatly in terms of the coding of space and the effort required to search. Here we describe a direct comparison between visually guided searches (as studied in visual search tasks) and foraging that is not based upon a visually distinct target, within the same context. The experiment was conducted in a novel apparatus, where search locations were indicated by an array of lights embedded in the floor. In visually guided conditions participants searched for a target defined by the presence of a feature (red target amongst green distractors) or the absence of a feature (green target amongst red and green distractors). Despite the expanded search scale and the different response requirements, these conditions followed the pattern found in conventional visual search paradigms: feature-present search latencies were not linearly related to display size, whereas feature-absent searches were longer as the number of distractors increased. In a non-visually guided foraging condition, participants searched for a target that was only visible once the switch was activated. This resulted in far longer latencies that rose markedly with display size. Compared to eye-movements in previous visual search studies, there were few revisit errors to previously inspected locations in this condition. This demonstrates the important distinction between visually guided and non-visually guided foraging processes, and shows that the visual search paradigm is an equivocal model for general search in any context. We suggest a comprehensive model of human spatial search behaviour needs to include search at a small and large scale as well as visually guided and non-visually guided search. <s> BIB038 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Previously we have shown that the eyes of expert breast imagers are attracted to the location ::: of a malignant mass in a mammogram in less than 2 seconds after image onset. Moreover, the longer ::: they take to visually fixate the location of the mass, the less likely it is that they will report it. We ::: conjectured that this behavior was due to the formation of the initial hypothesis about the image (i.e., ::: 'normal' - no lesions to report, or 'abnormal' - possible lesions to report). This initial hypothesis is ::: formed as a result of a difference template between the experts' expectations of the image and the ::: actual image. Hence, when the image is displayed, the expert detects the areas that do not correspond ::: to their 'a priori expectation', and these areas get assigned weights according to the magnitude of the ::: perturbation. The radiologist then uses eye movements to guide the high resolution fovea to each of ::: these locations, in order to resolve each perturbation. To accomplish this task successfully the ::: radiologist uses not only the local features in the area but also lateral comparisons with selected ::: background locations, and this comprises the radiologist's visual search strategy. Eye-position ::: tracking studies seem to suggest that no two radiologists search the breast parenchyma alike, which ::: makes one wonder whether successful search models can be developed. In this study we show that ::: there is more to the experts' search strategy than meets the eye. <s> BIB039 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The diffusion decision model allows detailed explanations of behavior in two-choice discrimination tasks. In this article, the model is reviewed to show how it translates behavioral data-accuracy, mean response times, and response time distributions-into components of cognitive processing. Three experiments are used to illustrate experimental manipulations of three components: stimulus difficulty affects the quality of information on which a decision is based; instructions emphasizing either speed or accuracy affect the criterial amounts of information that a subject requires before initiating a response; and the relative proportions of the two stimuli affect biases in drift rate and starting point. The experiments also illustrate the strong constraints that ensure the model is empirically testable and potentially falsifiable. The broad range of applications of the model is also reviewed, including research in the domains of aging and neurophysiology. <s> BIB040 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> In 1967 Ulric Neisser, studying how laypeople examined pictures, hypothesized that image ::: perception occurs in two stages, a pre-attentive stage in which the entire image is processed in ::: parallel, where a 'holistic' view of what is being displayed is formed, and a secondary stage in which ::: items or groups of items are examined by focal attention. Later, the proponents of Neisser's theory ::: suggested that the pre-attentive stage may bias the selection of the areas that will be subjected to ::: further analysis. This is easily seen in those dual interpretation figures; once one 'sees' the figure in ::: a certain way, it is very hard to instruct the eye-brain system to let go of that perception and 'see' ::: the figure in the alternative way. In medical image perception, Harold Kundel and Calvin Nodine ::: proposed a model of medical image interpretation that is based upon Neisser's two stages, and ::: have become so convinced of the influence of the 'holistic' view on the subsequent reading of the ::: image that they have recently questioned the traditional framework that determines how lesions are ::: found. In other words, as opposed to the traditional view of SEARCH THE IMAGE - DETECT A ::: POSSIBLE FINDING - IDENTIFY THE FINDING - DECIDE WHAT TO DO ABOUT THE IMAGE, ::: Kundel and Nodine have recently suggested a new framework: DETECT A POSSIBLE FINDING - ::: IDENTIFY THE FINDING - SEARCH THE IMAGE - DECIDE WHAT TO DO ABOUT THE IMAGE. ::: In light of this significant switch, we decided to investigate what happens when the 'holistic' view is ::: incorrect. <s> BIB041 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Double reading of chest x-rays is often used to ensure that fewer abnormalities are missed, but very little is known about how the search behavior of others affects observer performance. A series of experiments investigated whether radiographers benefit from knowing where another person looked for pulmonary nodules, and whether the expertise of the model providing the search behavior was a contributing factor. Experiment 1 compared the diagnostic performance of novice and experienced radiographers examining chest x-rays and found that both groups performed better when shown the search behavior of either a novice radiographer or an expert radiologist. Experiment 2 established that benefits in performance only arose when the eye movements shown were related to the search for nodules; however, only the novices' diagnostic performance consistently improved when shown the expert's search behavior. Experiment 3 reexamined the contribution of task, image, and the expertise of the model underlying this benefit. Consistent with Experiment 1, novice radiographers were better at identifying nodules when shown either a naive's search behavior or an expert radiologist's search behavior, but they demonstrated no improvement when shown a naive model not searching for nodules. Our results suggest that although the benefits of this form of attentional guidance may be short-lived, novices can scaffold their decisions based on the search behavior of others. <s> BIB042 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Visual search is often facilitated when the search display occasionally repeats, revealing a contextual-cueing effect. According to the associative-learning account, contextual cueing arises from associating the display configuration with the target location. However, recent findings emphasizing the importance of local context near the target have given rise to the possibility that low-level repetition priming may account for the contextual-cueing effect. This study distinguishes associative learning from local repetition priming by testing whether search is directed toward a target's expected location, even when the target is relocated. After participants searched for a T among Ls in displays that repeated 24 times, they completed a transfer session where the target was relocated locally to a previously blank location (Experiment 1) or to an adjacent distractor location (Experiment 2). Results revealed that contextual cueing decreased as the target appeared farther away from its expected location, ultima... <s> BIB043 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> An understanding of radiologists’ visual and interpretive behaviors, explored in conjunction with the capabilities of innovative advanced technologies, may provide useful new paradigms for interpreting results from medical imaging examinations. <s> BIB044 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> PURPOSE ::: To compare the content, clarity, and clinical usefulness of conventional (ie, free-form) and structured radiology reports of body computed tomographic (CT) scans, as evaluated by referring physicians, attending radiologists, and radiology fellows at a tertiary care cancer center. ::: ::: ::: MATERIALS AND METHODS ::: The institutional review board approved the study as a quality improvement initiative; no written consent was required. Three radiologists, three radiology fellows, three surgeons, and two medical oncologists evaluated 330 randomly selected conventional and structured radiology reports of body CT scans. For nonradiologists, reports were randomly selected from patients with diagnoses relevant to the physician's area of specialization. Each physician read 15 reports in each format and rated both the content and clarity of each report from 1 (very dissatisfied or very confusing) to 10 (very satisfied or very clear). By using a previously published radiology report grading scale, physicians graded each report's effectiveness in advancing the patient's position on the clinical spectrum. Mixed-effects models were used to test differences between report types. ::: ::: ::: RESULTS ::: Mean content satisfaction ratings were 7.61 (95% confidence interval [CI]: 7.12, 8.16) for conventional reports and 8.33 (95% CI: 7.82, 8.86) for structured reports, and the difference was significant (P < .0001). Mean clarity satisfaction ratings were 7.45 (95% CI: 6.89, 8.02) for conventional reports and 8.25 (95% CI: 7.68, 8.82) for structured reports, and the difference was significant (P < .0001). Grade ratings did not differ significantly between conventional and structured reports. ::: ::: ::: CONCLUSION ::: Referring clinicians and radiologists found that structured reports had better content and greater clarity than conventional reports. <s> BIB045 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Active exploration of the visual world depends on sequential shifts of gaze that bring prioritized regions of a scene into central vision. The efficiency of this system is commonly attributed to a mechanism of “inhibition of return” (IOR) that discourages re-examination of previously-visited locations. Such a process is fundamental to computational models of attentional selection and paralleled by neurophysiological observations of inhibition of target-related activity in visuomotor areas. However, studies examining eye movements in naturalistic visual scenes appear to contradict the hypothesis that IOR promotes exploration. Instead, these reports reveal a surprisingly strong tendency to shift gaze back to the previously fixated location, suggesting that refixations might even be facilitated under natural conditions. Here we resolve this apparent contradiction, based on a probabilistic analysis of gaze patterns recorded during both free-viewing and search of naturalistic scenes. By simulating saccadic selection based on instantaneous influences alone, we show that the observed frequency of return saccades is in fact substantially less than predicted for a memoryless system, demonstrating that refixation is actively inhibited under natural viewing conditions. Furthermore, these observations reveal that gaze history significantly influences the way in which natural scenes are explored, contrary to accounts that suggest visual search has no memory. <s> BIB046 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> In visual search tasks, observers look for targets in displays or scenes containing distracting, non-target items. Most of the research on this topic has concerned the finding of those targets. Search termination is a less thoroughly studied topic. When is it time to abandon the current search? The answer is fairly straight forward when the one and only target has been found (There are my keys.). The problem is more vexed if nothing has been found (When is it time to stop looking for a weapon at the airport checkpoint?) or when the number of targets is unknown (Have we found all the tumors?). This chapter reviews the development of ideas about quitting time in visual search and offers an outline of our current theory. <s> BIB047 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> We examined how the ability to detect lung nodules in chest x-ray inspection is reflected in experience-related differences in visual search and decision making, and whether the eye-tracking metric time-to-first hit showed systematic decreases across expertise levels are examined. In the study decision making improved with expertise, however, time-to-first fixate a nodule showed only a non-significant trend to decrease with expertise. Surprisingly, naive and expert observers allocated less visual attention at nodules compared with first and third year radiography students. This similarity in visual attention at nodules but not in decision making was explained by the fact that naive observers were more likely to fixate and make errors on distracter regions. Time-to-first hit has been linked to expert performance in mammography, but in this study was not sufficiently sensitive to demonstrate clear linear improvements across expertise groups. This brings into question the use of this metric as an indirect measure of rapid initial holistic processing. <s> BIB048 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The purpose of this study was to examine individual differences in eye-movement behavior. Six metrics (Fixation Rate, Duration, and Size; Saccade Amplitude; Micro-Saccade Rate and Amplitude) were used to measure individuals’ eye-movement behavior profiles (EmBP). We replicate previous research (Andrews & Coppola, 1999; Castelhano & Henderson, 2008) by finding consistent individual differences in fixation duration and saccade amplitude across tasks, and present new findings of stable idiosyncrasies in measures of fixational eye-movement (Fixation Size, Micro-Saccade Rate and Amplitude). Moreover, we observed consistent inter-metric correlations across tasks (e.g., individuals that exhibited relatively high Fixation Rates also presented relative low Micro-Saccade Rates and relatively high Micro-Saccade Amplitudes). Factor Analysis linked the six EmBP metrics together with a single factor, which we speculate might be related to the operational effectiveness of the attentional system, given that individual factor scores were correlated with scores on a self-report measure of attentional function. Normal subjects with relatively high scores on this attention-deficit measure exhibited relatively frequent fixations of short duration and large spatial extent, and relatively infrequent micro-saccades of large amplitude. This EmBP is similar to a general pattern of eye-movement behavior observed with ADHD individuals – difficulty controlling eye movements, maintaining fixation, and inhibiting intrusive saccades. Results of this study indicate that normal individuals exhibit idiosyncratic EmBPs that are quite stable across tasks and are related to attentional ability. <s> BIB049 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> OBJECTIVE ::: Our aim was to examine the specificity of the effects of acquiring expertise on visual working memory (VWM) and the degree to which higher levels of experience within the domain of expertise are associated with more efficient use of VWM. ::: ::: ::: BACKGROUND ::: Previous research is inconsistent on whether expertise effects are specific to the area of expertise or generalize to other tasks that also involve the same cognitive processes. It is also unclear whether more training and/or experience will lead to continued improvement on domain-relevant tasks or whether a plateau could be reached. ::: ::: ::: METHOD ::: In Experiment I, veterinary medicine students completed a one-shot visual change detection task. In Experiment 2, veterinarians completed a flicker change detection task. Both experiments involved stimuli specific to the domain of radiology and general stimuli. ::: ::: ::: RESULTS ::: In Experiment I, veterinary medicine students who had completed an "eyes-on" radiological training demonstrated a domain-specific effect in which performance was better on the domain-specific stimuli than on the domain-general stimuli. In Experiment 2, veterinarians again showed a domain-specific effect, but performance was unrelated to the amount of experience veterinarians had accumulated. ::: ::: ::: CONCLUSION ::: The effect of experience is domain specific and occurs during the first few years of training, after which a plateau is reached. ::: ::: ::: APPLICATION ::: VWM training in one domain may not lead to improved performance on other VWM tasks. In acquiring expertise, eyes-on training is important initially, but continued experience may not be associated with further improvements in the efficiency of VWM. <s> BIB050 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> We are often not explicitly aware of the location of our spatial attention, despite its influence on our perception and cognition. During a picture memory task, we asked whether people could later recognise their eye fixations in a two-alternative test. In three separate experiments, participants performed above chance when discriminating their own fixation patterns from random locations or locations fixated in a different image. Recognition was much poorer when the task was to spot your own versus someone else's fixations on the same stimulus, but performance remained better than chance. That we are sensitive to our own scan patterns has implications for perception, memory, and meta-cognition. <s> BIB051 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Many modern theories propose that perceptual information is represented by the sensorimotor activity elicited by the original stimulus. Scanpath theory (Noton & Stark, 1971) predicts that reinstating a sequence of eye fixations will help an observer recognize a previously seen image. However, the only studies to investigate this are correlational ones based on calculating scanpath similarity. We therefore describe a series of 5 experiments that constrain the fixations during encoding or recognition of images in order to manipulate scanpath similarity. Participants encoded a set of images and later had to recognize those that they had seen. They spontaneously selected regions that they had fixated during encoding (Experiment 1), and this was a predictor of recognition accuracy. Yoking the parts of the image available at recognition to the encoded scanpath led to better memory performance than randomly selected image regions (Experiment 2), and this could not be explained by the spatial distribution of locations (Experiment 3). However, there was no recognition advantage for re-viewing one's own fixations versus someone else's (Experiment 4) or for retaining their serial order (Experiment 5). Therefore, although it is beneficial to look at encoded regions, there is no evidence that scanpaths are stored or that scanpath recapitulation is functional in scene memory. This paradigm provides a controlled way of studying the integration of scene content, spatial structure, and oculomotor signals, with consequences for the perception, representation, and retrieval of visual information. © American Psychological Association. <s> BIB052 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> In two experiments we investigated the relationship between eye movements and performance in visual search tasks of varying difficulty. Experiment 1 provided evidence that a single process is used for search among static and moving items. Moreover, we estimated the functional visual field (FVF) from the gaze coordinates and found that its size during visual search shrinks with increasing task difficulty. In ::: Experiment 2, we used a gaze-contingent window and confirmed the validity of the size estimates. The experiment also revealed that breakdown in robustness against item motion is related to item-by-item search, rather than search difficulty per se. We argue that visual search is an eye-movement-based process that works on a continuum, from almost parallel (where many items can be processed within a fixation) to completely serial (where only one item can be processed within a fixation). <s> BIB053 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> We assessed fixation planning in visual search in two experiments by tracking participants' eye movements while they each searched for a simple target (a T shape) among a set of distractors (L shapes). On some trials, the search display was briefly interrupted with a blank screen and, following a randomly determined period of elapsed time, the search display was reinstated. In Experiment 1, we found that search continued during the interruption but fixation durations were increased and the accuracy of saccadic targeting was impaired. A MLM demonstrated that acuity played a role in determining whether fixated missing objects were processed during the interruption and that fixation planning was uninfluenced by the length of time available prior to the interruption. In Experiment 2, to check that fixations in the interruption periods were not random, half the distractors were blue (the target was blue as well) and half were yellow. All of the findings from Experiment 1 were replicated and the majority of fixations in the interruption period landed upon blue distractors. Results are discussed in relation to the capacity, time course, and format of fixation plans in visual search. <s> BIB054 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Radiology practice guidelines have been developed to help radiologists achieve quality and safety in their clinical practice. One means to promote the use of practice guidelines in radiology is through the wider use of reporting templates, also known as "structured reporting." This article presents specific examples in which radiology reporting templates can promote adherence to guidelines, gather data for quality improvement efforts, and facilitate compliance with performance incentive programs. <s> BIB055 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Animals, including humans, engage in many forms of foraging behavior in which resources are collected from the world. This paper examines human foraging in a visual search context. A real-world analog would be berry picking. The selection of individual berries is not the most interesting problem in such a task. Of more interest is when does a forager leave one patch or berry bush for the next one? Marginal Value Theorem (MVT; Charnov, 1976) predicts that observers will leave a patch when the instantaneous yield from that patch drops below the average yield from the entire “field.” Experiments 1, 2, 3, and 4 show that MVT gives a good description of human behavior for roughly uniform collections of patches. Experiments 5 and 6 show strong departures from MVT when patch quality varies and when visual information is degraded. <s> BIB056 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> During manually-assisted search, where participants must actively manipulate search items, it has been reported that participants will often select and move the target of search itself without recognizing it (Solman et al., 2012a). In two experiments we explore the hypothesis that this error results from a naturally-arising strategy that decouples perception and action during search, enabling motor interactions with items to outpace the speed of perceptual analysis. In Experiment 1, we report that the error is prevalent for both mouse and touch-screen interaction modes, and is uninfluenced by speeding or slowing instructions – ruling out these task-specific details as causes of the error. In Experiment 2 we manipulate motor speed, and show that reducing the speed of individual movements during search leads to a reduction in error rates. These findings support the conclusion that the error results from incoordination between motor and perceptual processes, with motor processes outpacing perceptual abilities. <s> BIB057 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The present eye-movement study assessed the effect of expertise on eye-movement behaviour during image perception in the medical domain. To this end, radiologists, computed-tomography radiographers and psychology students were exposed to nine volumes of multi-slice, stack-view, axial computed-tomography images from the upper to the lower part of the abdomen with or without abnormality. The images were presented in succession at low, medium or high speed, while the participants had to detect enlarged lymph nodes or other visually more salient abnormalities. The radiologists outperformed both other groups in the detection of enlarged lymph nodes and their eye-movement behaviour also differed from the other groups. Their general strategy was to use saccades of shorter amplitude than the two other participant groups. In the presence of enlarged lymph nodes, they increased the number of fixations on the relevant areas and reverted to even shorter saccades. In volumes containing enlarged lymph nodes, radiologists' fixation durations were longer in comparison to their fixation durations in volumes without enlarged lymph nodes. More salient abnormalities were detected equally well by radiologists and radiographers, with both groups outperforming psychology students. However, to accomplish this, radiologists actually needed fewer fixations on the relevant areas than the radiographers. On the basis of these results, we argue that expert behaviour is manifested in distinct eye-movement patterns of proactivity, reactivity and suppression, depending on the nature of the task and the presence of abnormalities at any given moment. <s> BIB058 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Mean fixation duration and mean saccade amplitude during active viewing tasks differ from person to person. Previous studies have shown that these individual differences tend to be stable across at least some tasks, suggesting that they may reflect underlying traits associated with individuals. However, whether these individual differences are also stable over time has not been established. The present study established stable individual differences in mean fixation duration and mean saccade amplitude across 4 viewing tasks, showed that the observed individual differences are stable over several days, and extended these results to standard deviations of fixation duration and saccade amplitude. The results have implications for theories of eye movement control and for using eye movement characteristics as individual difference measures. (PsycINFO Database Record (c) 2014 APA, all rights reserved). Language: en <s> BIB059 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Eye scanning patterns while viewing pictures have provided valuable information in many domains of visual cognition. Such patterns are determined by the type of image viewed (e.g., faces, scenes) as well as the task individuals are asked to perform (e.g., visual search, memory). Here we show that another key factor that significantly influences eye scanning patterns but has been mostly overlooked is the individual observer. During face viewing, we found that individuals showed diverse scanning patterns that, in many cases, were inconsistent with the typical triangular shape pattern that is commonly observed when eye scanning patterns are averaged across individuals. These idiosyncratic eye scanning patterns were not random but highly stable even when examined 18 months later. Interestingly, these eye-tracking patterns were not predictive of behavioral performance. Such stable and unique scanning patterns may represent a specific behavioral trait/signature and be formed early in development, reflecting idiosyncratic strategies for performing visual recognition tasks. <s> BIB060 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Human observers often adopt rigid scanning strategies in visual search tasks, even though this may lead to suboptimal performance. Here we ask whether specific levels of saccadic amplitude variability may be induced in a visual search task using reinforcement learning. We designed a new gaze-contingent visual foraging task in which finding a target among distractors was made contingent upon specific saccadic amplitudes. When saccades of rare amplitudes led to displaying the target, the U values (measuring uncertainty) increased by 54.89% on average. They decreased by 41.21% when reinforcing frequent amplitudes. In a noncontingent control group no consistent change in variability occurred. A second experiment revealed that this learning transferred to conventional visual search trials. These results provide experimental support for the importance of reinforcement learning for saccadic amplitude variability in visual search. <s> BIB061 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Current literature shows that radiologist experience does not affect detection tasks when the object does not require medical training to detect. However, the research was never sufficiently detailed to examine if the contrast detection threshold is also the same for radiologists versus nonradiologists. Previously, contrast threshold research was performed predominantly on nonradiologists. Therefore, any differences could lead to over- or under-estimation of the performance capabilities of radiologists. Fourteen readers, evenly divided between radiologists and nonradiologists, read a set of 150 mammogram-like images. The study was performed with the location of the objects known and unknown, requiring two separate readings. No difference in the contrast detection threshold between reader groups for either the location-unknown (4.9 just noticeable differences) or location-known (3.3 just noticeable differences) images was seen. The standard deviation for the location-unknown condition had no difference (p 0.91). But for the location-known condition, a significant difference (p 0.0009) was seen between radiologists and nonradiologists. No difference in contrast detection based on reader experience was observed, but decreased variance was seen with radiologists in the location-known condition. <s> BIB062 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> OBJECTIVE ::: The radiology report serves as the primary method of communication about imaging findings. Traditional free-text (i.e., unstructured) radiology reporting entails dictating in a stream-of-consciousness manner. Structured reporting aims to standardize the format and lexicon used in reports. This standardization may improve the communication of findings, allowing ease of reading and comprehension. A structured reporting template may also be used as a checklist while reviewing a case, which may facilitate focused attention and analysis. The goal of this study was to compare unstructured and structured reports in terms of their completeness and effectiveness. ::: ::: ::: MATERIALS AND METHODS ::: Radiology trainees were given an educational lecture on the background of reporting and were provided with a structured reporting template for dictating chest radiographs. Twelve trainees completed the study. Sixty reports from before and 60 reports from after the intervention were each independently scored by four blinded physician raters for completeness and effectiveness. ::: ::: ::: RESULTS ::: Structured reports were found to be statistically significantly more complete and more effective than unstructured reports (mean completeness score, 4.42 vs 3.99, p<0.001; mean effectiveness score, 4.11 vs 3.85, p<0.001). A combined score was calculated for each report and was higher for the structured reports (mean combined score, 8.54 vs 7.83, p<0.001). ::: ::: ::: CONCLUSION ::: Structured chest radiograph reports were more complete and more effective than unstructured chest radiograph reports. Although additional studies are needed for validation, this study suggests that structured reporting may represent an improved reporting method for radiologists. <s> BIB063 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The increasing use of medical checklists to promote patient safety raises the question of their utility in diagnostic radiology. This study evaluates the efficacy of a checklist-style reporting template in reducing resident misses on cervical spine CT examinations. A checklist-style reporting template for cervical spine CTs was created at our institution and mandated for resident preliminary reports. Ten months after implementation of the template, we performed a retrospective cohort study comparing rates of emergent pathology missed on reports generated with and without the checklist-style reporting template. In 1,832 reports generated without using the checklist-style template, 25 (17.6 %) out of 142 emergent findings were missed. In 1,081 reports generated using the checklist-style template, 13 (11.9 %) out of 109 emergent findings were missed. The decrease in missed pathology was not statistically significant (p = 0.21). However, larger differences were noted in the detection of emergent non-fracture findings, with 17 (28.3 %) out of 60 findings missed on reports without use of the checklist template and 5 (9.3 %) out of 54 findings missed on reports using the checklist template, representing a statistically significant decrease in missed non-fracture findings (p = 0.01). The use of a checklist-style structured reporting template resulted in a statistically significant decrease in missed non-fracture findings on cervical spine CTs. The lack of statistically significant change in missed fractures was expected given that residents’ search patterns naturally include fracture detection. Our findings suggest that the use of checklists in structured reporting may increase diagnostic accuracy. <s> BIB064 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Subjects searched for low- or high-prevalence targets among static nonoverlapping items or items piled in heaps that could be moved using a computer mouse. We replicated the classical prevalence effect both in visual search and when unpacking items from heaps, with more target misses under low prevalence. Moreover, we replicated our previous finding that while unpacking, people often move the target item without noticing (the unpacking error) and determined that these errors also increase under low prevalence. On the basis of a comparison of item movements during the manually-assisted search and eye movements during static visual search, we suggest that low prevalence leads to broadly reduced diligence during search but that the locus of this reduced diligence depends on the nature of the task. In particular, while misses during visual search often arise from a failure to inspect all of the items, misses during manually-assisted search more often result from a failure to adequately inspect individual items. Indeed, during manually-assisted search, over 90 % of target misses occurred despite subjects having moved the target item during search. <s> BIB065 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> RATIONALE AND OBJECTIVES ::: To examine the effect of changes in utilization and advances in cross-sectional imaging on radiologists' workload. ::: ::: ::: MATERIALS AND METHODS ::: All computed tomography (CT) and magnetic resonance imaging (MRI) examinations performed at a single institution between 1999 and 2010 were identified and associated with the total number of images for each examination. Annual trends in institutional numbers of interpreted examinations and images were translated to changes in daily workload for the individual radiologist by normalizing to the number of dedicated daily CT and MRI work assignments, assuming a 255-day/8-hour work day schedule. Temporal changes in institutional and individual workload were assessed by Sen's slope analysis (Q = median slope) and Mann-Kendall test (Z = Z statistic). ::: ::: ::: RESULTS ::: From 1999 to 2010, a total of 1,517,149 cross-sectional imaging studies (CT = 994,471; MRI = 522,678) comprising 539,210,581 images (CT = 339,830,947; MRI = 199,379,634) were evaluated at our institution. Total annual cross-sectional studies steadily increased from 84,409 in 1999 to 147,336 in 2010, representing a twofold increase in workload (Q = 6465/year, Z = 4.2, P < .0001). Concomitantly, the number of annual departmental cross-sectional images interpreted increased from 9,294,140 in 1990 to 94,271,551 in 2010, representing a 10-fold increase (Q = 8707876/year, Z = 4.5, P < .0001). Adjusting for staffing changes, the number of images requiring interpretation per minute of every workday per staff radiologist increased from 2.9 in 1999 to 16.1 in 2010 (Q = 1.7/year, Z = 4.3, P < .0001). ::: ::: ::: CONCLUSIONS ::: Imaging volumes have grown at a disproportionate rate to imaging utilization increases at our institution. The average radiologist interpreting CT or MRI examinations must now interpret one image every 3-4 seconds in an 8-hour workday to meet workload demands. <s> BIB066 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> PURPOSE ::: To determine the effectiveness of radiologists' search, recognition, and acceptance of lung nodules on computed tomographic (CT) images by using eye tracking. ::: ::: ::: MATERIALS AND METHODS ::: This study was performed with a protocol approved by the institutional review board. All study subjects provided informed consent, and all private health information was protected in accordance with HIPAA. A remote eye tracker was used to record time-varying gaze paths while 13 radiologists interpreted 40 lung CT images with an average of 3.9 synthetic nodules (5-mm diameter) embedded randomly in the lung parenchyma. The radiologists' gaze volumes ( GV gaze volume s) were defined as the portion of the lung parenchyma within 50 pixels (approximately 3 cm) of all gaze points. The fraction of the total lung volume encompassed within the GV gaze volume s, the fraction of lung nodules encompassed within each GV gaze volume (search effectiveness), the fraction of lung nodules within the GV gaze volume detected by the reader (recognition-acceptance effectiveness), and overall sensitivity of lung nodule detection were measured. ::: ::: ::: RESULTS ::: Detected nodules were within 50 pixels of the nearest gaze point for 990 of 992 correct detections. On average, radiologists searched 26.7% of the lung parenchyma in 3 minutes and 16 seconds and encompassed between 86 and 143 of 157 nodules within their GV gaze volume s. Once encompassed within their GV gaze volume , the average sensitivity of nodule recognition and acceptance ranged from 47 of 100 nodules to 103 of 124 nodules (sensitivity, 0.47-0.82). Overall sensitivity ranged from 47 to 114 of 157 nodules (sensitivity, 0.30-0.73) and showed moderate correlation (r = 0.62, P = .02) with the fraction of lung volume searched. ::: ::: ::: CONCLUSION ::: Relationships between reader search, recognition and acceptance, and overall lung nodule detection rate can be studied with eye tracking. Radiologists appear to actively search less than half of the lung parenchyma, with substantial interreader variation in volume searched, fraction of nodules included within the search volume, sensitivity for nodules within the search volume, and overall detection rate. <s> BIB067 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> PURPOSE ::: To assess the completeness and clarity of current free-form radiology reports for pancreatic cancer staging by evaluating them against the elements of the RSNA CT oncology primary pancreas mass dictation template. ::: ::: ::: METHODS ::: This retrospective study was approved by our Institutional Review Board (IRB). 295 free-form computed tomography (CT) reports for baseline staging of pancreatic cancer (PC) generated between August 2008 and December 2010 were evaluated by one of two radiologists with expertise in pancreatic cancer imaging. Reports which indicated that metastatic disease was present were excluded. The completeness and clarity of the reports were analyzed against the elements of the RSNA CT pancreas mass dictation template. Fisher's exact tests were used to analyze differences by year and type of radiologist. ::: ::: ::: RESULTS ::: Primary lesion location, size, and effect on bile duct (BD) were provided in 93.9% (277/295), 69.8% (206/295), and 67.5% (199/295) of reports, respectively. Standard terms to describe vascular involvement were used in 47.5% (140/295) of reports. In 20.3% (60/295), the resectability status could not be defined based on the report alone. In 36.9% (109/295) of reports, review of CT images was necessary to understand vascular involvement. Radiologists expert in pancreatic oncology had a higher proportion of reports using standardized terminology and reports in which vascular involvement was understood without revisiting the images. ::: ::: ::: CONCLUSIONS ::: Free-form reports were more likely to use ambiguous terminology and/or require review of the actual images for understanding resectability status. The use of a standardized reporting template may improve the usefulness of pancreatic cancer staging reports. <s> BIB068 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> OBJECTIVE. The purpose of this article is to evaluate the quality of reports of knee MRI examinations in form, content, and diagnosis and to assess the effect of three different quality improvement measures. MATERIALS AND METHODS. Reports of 500 knee MRI examinations (first round, or baseline) were reviewed retrospectively by five musculoskeletal radiologists. Fifteen different criteria were assessed for formal and content-related quality of reports. Diagnostic discrepancies were categorized using a 5-point scale, as follows: I, no deviation; II, undetected finding, clinically irrelevant; III, wrong interpretation of finding, clinically irrelevant; IV, undetected finding, clinically relevant; and V, wrong interpretation of finding, clinically relevant. Then three different quality improvement measures were applied prospectively to a total of 510 consecutive reports: a quiet work environment, double reading, and the use of a structured report template. These 510 knee MRI reports (second round) were evaluat... <s> BIB069 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Purpose: Signal detection on 3D medical images depends on many factors, such as foveal and peripheral vision, the type of signal, and background complexity, and the speed at which the frames are displayed. In this paper, the authors focus on the speed with which radiologists and naive observers search through medical images. Prior to the study, the authors asked the radiologists to estimate the speed at which they scrolled through CT sets. They gave a subjective estimate of 5 frames per second (fps). The aim of this paper is to measure and analyze the speed with which humans scroll through image stacks, showing a method to visually display the behavior of observers as the search is made as well as measuring the accuracy of the decisions. This information will be useful in the development of model observers, mathematical algorithms that can be used to evaluate diagnostic imaging systems. Methods: The authors performed a series of 3D 4-alternative forced-choice lung nodule detection tasks on volumetric stacks of chest CT images iteratively reconstructed in lung algorithm. The strategy used by three radiologists and three naive observers was assessed using an eye-tracker in order to establish where their gaze was fixed during the experiment and to verify that when a decision was made, a correct answer was not due only to chance. In a first set of experiments, the observers were restricted to read the images at three fixed speeds of image scrolling and were allowed to see each alternative once. In the second set of experiments, the subjects were allowed to scroll through the image stacks at will with no time or gaze limits. In both static-speed and free-scrolling conditions, the four image stacks were displayed simultaneously. All trials were shown at two different image contrasts. Results: The authors were able to determine a histogram of scrolling speeds in frames per second. The scrolling speed of the naive observers and the radiologists at the moment the signal was detected was measured at 25–30 fps. For the task chosen, the performance of the observers was not affected by the contrast or experience of the observer. However, the naive observers exhibited a different pattern of scrolling than the radiologists, which included a tendency toward higher number of direction changes and number of slices viewed. Conclusions: The authors have determined a distribution of speeds for volumetric detection tasks. The speed at detection was higher than that subjectively estimated by the radiologists before the experiment. The speed information that was measured will be useful in the development of 3D model observers, especially anthropomorphic model observers which try to mimic human behavior. <s> BIB070 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> People are surprisingly bad at knowing where they have looked in a scene. We tested participants' ability to recall their own eye movements in 2 experiments using natural or artificial scenes. In each experiment, participants performed a change-detection (Exp.1) or search (Exp.2) task. On 25% of trials, after 3 seconds of viewing the scene, participants were asked to indicate where they thought they had just fixated. They responded by making mouse clicks on 12 locations in the unchanged scene. After 135 trials, observers saw 10 new scenes and were asked to put 12 clicks where they thought someone else would have looked. Although observers located their own fixations more successfully than a random model, their performance was no better than when they were guessing someone else's fixations. Performance with artificial scenes was worse, though judging one's own fixations was slightly superior. Even after repeating the fixation-location task on 30 scenes immediately after scene viewing, performance was far from the prediction of an ideal observer. Memory for our own fixation locations appears to add next to nothing beyond what common sense tells us about the likely fixations of others. These results have important implications for socially important visual search tasks. For example, a radiologist might think he has looked at "everything" in an image, but eye tracking data suggest that this is not so. Such shortcomings might be avoided by providing observers with better insights of where they have looked. (PsycINFO Database Record <s> BIB071 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Eye tracking research has been conducted for decades to gain understanding of visual diagnosis such as in radiology. For educational purposes, it is important to identify visual search patterns that are related to high perceptual performance and to identify effective teaching strategies. This review of eye-tracking literature in the radiology domain aims to identify visual search patterns associated with high perceptual performance. Databases PubMed, EMBASE, ERIC, PsycINFO, Scopus and Web of Science were searched using ‘visual perception’ OR ‘eye tracking’ AND ‘radiology’ and synonyms. Two authors independently screened search results and included eye tracking studies concerning visual skills in radiology published between January 1, 1994 and July 31, 2015. Two authors independently assessed study quality with the Medical Education Research Study Quality Instrument, and extracted study data with respect to design, participant and task characteristics, and variables. A thematic analysis was conducted to extract and arrange study results, and a textual narrative synthesis was applied for data integration and interpretation. The search resulted in 22 relevant full-text articles. Thematic analysis resulted in six themes that informed the relation between visual search and level of expertise: (1) time on task, (2) eye movement characteristics of experts, (3) differences in visual attention, (4) visual search patterns, (5) search patterns in cross sectional stack imaging, and (6) teaching visual search strategies. Expert search was found to be characterized by a global-focal search pattern, which represents an initial global impression, followed by a detailed, focal search-to-find mode. Specific task-related search patterns, like drilling through CT scans and systematic search in chest X-rays, were found to be related to high expert levels. One study investigated teaching of visual search strategies, and did not find a significant effect on perceptual performance. Eye tracking literature in radiology indicates several search patterns are related to high levels of expertise, but teaching novices to search as an expert may not be effective. Experimental research is needed to find out which search strategies can improve image perception in learners. <s> BIB072 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Abstract This paper introduces the “hybrid foraging” paradigm. In typical visual search tasks, observers search for one instance of one target among distractors. In hybrid search, observers search through visual displays for one instance of any of several types of target held in memory. In foraging search, observers collect multiple instances of a single target type from visual displays. Combining these paradigms, in hybrid foraging tasks observers search visual displays for multiple instances of any of several types of target (as might be the case in searching the kitchen for dinner ingredients or an X-ray for different pathologies). In the present experiment, observers held 8–64 target objects in memory. They viewed displays of 60–105 randomly moving photographs of objects and used the computer mouse to collect multiple targets before choosing to move to the next display. Rather than selecting at random among available targets, observers tended to collect items in runs of one target type. Reaction time (RT) data indicate searching again for the same item is more efficient than searching for any other targets, held in memory. Observers were trying to maximize collection rate. As a result, and consistent with optimal foraging theory, they tended to leave 25–33% of targets uncollected when moving to the next screen/patch. The pattern of RTs shows that while observers were collecting a target item, they had already begun searching memory and the visual display for additional targets, making the hybrid foraging task a useful way to investigate the interaction of visual and memory search. <s> BIB073 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Purpose To establish potential markers of visual expertise in eye movement (EM) patterns of early residents, advanced residents, and specialists who interpret abdominal computed tomography (CT) studies. Materials and Methods The institutional review board approved use of anonymized CT studies as research materials and to obtain anonymized eye-tracking data from volunteers. Participants gave written informed consent. Early residents (n = 15), advanced residents (n = 14), and specialists (n = 12) viewed 26 abdominal CT studies as a sequence of images at either 3 or 5 frames per second while EMs were recorded. Data were analyzed by using linear mixed-effects models. Results Early residents' detection rate decreased with working hours (odds ratio, 0.81; 95% confidence interval [CI]: 0.73, 0.91; P = .001). They detected less of the low visual contrast (but not of the high visual contrast) lesions (45% [13 of 29]) than did specialists (62% [18 of 29]) (odds ratio, 0.39; 95% CI: 0.25, 0.61; P < .001) or advanced residents (56% [16 of 29]) (odds ratio, 0.55; 95% CI: 0.33, 0.93; P = .024). Specialists and advanced residents had longer fixation durations at 5 than at 3 frames per second (specialists: β = .01; 95% CI: .004, .026; P = .008; advanced residents: β = .04; 95% CI: .03, .05; P < .001). In the presence of lesions, saccade lengths of specialists shortened more than those of advanced (β = .02; 95% CI: .007, .04; P = .003) and of early residents (β = .02; 95% CI: .008, 0.04; P = .003). Irrespective of expertise, high detection rate correlated with greater reduction of saccade length in the presence of lesions (β = -.10; 95% CI: -.16, -.04; P = .002) and greater increase at higher presentation speed (β = .11; 95% CI: .04, .17; P = .001). Conclusion Expertise in CT reading is characterized by greater adaptivity in EM patterns in response to the demands of the task and environment. © RSNA, 2016 Online supplemental material is available for this article. <s> BIB074 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Following a baseline demographic survey, 87 pathologists interpreted 240 digital whole slide images of breast biopsy specimens representing a range of diagnostic categories from benign to atypia, ductal carcinoma in situ, and invasive cancer. A web-based viewer recorded pathologists’ behaviors while interpreting a subset of 60 randomly selected and randomly ordered slides. To characterize diagnostic search patterns, we used the viewport location, time stamp, and zoom level data to calculate four variables: average zoom level, maximum zoom level, zoom level variance, and scanning percentage. Two distinct search strategies were confirmed: scanning is characterized by panning at a constant zoom level, while drilling involves zooming in and out at various locations. Statistical analysis was applied to examine the associations of different visual interpretive strategies with pathologist characteristics, diagnostic accuracy, and efficiency. We found that females scanned more than males, and age was positively correlated with scanning percentage, while the facility size was negatively correlated. Throughout 60 cases, the scanning percentage and total interpretation time per slide decreased, and these two variables were positively correlated. The scanning percentage was not predictive of diagnostic accuracy. Increasing average zoom level, maximum zoom level, and zoom variance were correlated with over-interpretation. <s> BIB075 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Diagnosing certain fractures in conventional radiographs can be a difficult task, usually taking years to master. Typically, students are trained ad-hoc, in a primarily-rule based fashion. Our study investigated whether students can more rapidly learn to diagnose proximal neck of femur fractures via perceptual training, without having to learn an explicit set of rules. One hundred and thirty-nine students with no prior medical or radiology training were shown a sequence of plain film X-ray images of the right hip and for each image were asked to indicate whether a fracture was present. Students were told if they were correct and the location of any fracture, if present. No other feedback was given. The more able students achieved the same level of accuracy as board certified radiologists at identifying hip fractures in less than an hour of training. Surprisingly, perceptual learning was reduced when the training set was constructed to over-represent the types of images participants found more difficult to categorise. Conversely, repeating training images did not reduce post-training performance relative to showing an equivalent number of unique images. Perceptual training is an effective way of helping novices learn to identify hip fractures in X-ray images and should supplement the current education programme for students. <s> BIB076 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> PURPOSE ::: Systematic viewing of images is widely advocated in radiology; it is expected to lead to complete coverage of images and consequently more detection of abnormalities. Evidence on the efficacy of teaching systematic viewing to students is conflicting. The aim of this study was to investigate the effects of teaching systematic viewing to final-year medical students on systematicity of viewing behavior, coverage of the image, and detection. ::: ::: ::: METHODS ::: Final-year medical students (n = 60) viewed 10 chest radiographs in a first series before training and another 10 radiographs in a second series after training. Between series, students were taught basic chest radiographic viewing, in either a systematic or a nonsystematic manner. With eye tracking, systematicity (Levenshtein distances), coverage (percentage of image viewed), and detection (sensitivity and specificity) were measured. ::: ::: ::: RESULTS ::: In a mixed two-by-two design, significantly higher sensitivity was found after training compared with before training (F1,55 = 6.68, P = .012, ηp2 = .11) but no significant effect for type of training (F1,55 = 1.24, P = .30) and no significant interaction effect (F1,55 = 0.12, P = .73). Thus, training in systematic viewing was not superior to training in nonsystematic viewing. A significant interaction of training type and time of viewing was found on systematicity (F1,49 = 20.0, P < .01, ηp2 = .29) in favor of the systematic viewing group. No significant interaction was found for coverage (F1,49 = 0.43, P = .51) or specificity (F1,55 = .124, P = .73). ::: ::: ::: CONCLUSIONS ::: Both training types showed similar increases in sensitivity. Therefore, it might be advisable to pay less attention to systematic viewing and more attention to content, such as the radiologic appearances of diseases. <s> BIB077 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> From the earliest recordings of eye movements during active scene viewing to the present day, researchers have commonly reported individual differences in eye movement scan patterns under constant stimulus and task demands. These findings suggest viewer individual differences may be important for understanding gaze control during scene viewing. However, the relationship between scan patterns and viewer individual differences during scene viewing remains poorly understood because scan patterns are difficult to analyze. The present study uses a powerful technique called Successor Representation Scanpath Analysis (Hayes, Petrov, & Sederberg, 2011, 2015) to quantify the strength of the association between individual differences in scan patterns during real-world scene viewing and individual differences in viewer intelligence, working memory capacity, and speed of processing. The results of this analysis revealed individual differences in scan patterns that explained more than 40% of the variance in viewer intelligence and working memory capacity measures, and more than a third of the variance in speed of processing measures. The theoretical implications of our findings for models of gaze control and avenues for future individual differences research are discussed. <s> BIB078 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Abstract. Identifying if participants with differing diagnostic accuracy and visual search behavior during radiologic tasks also differ in nonradiologic tasks is investigated. Four clinician groups with different radiologic experience were used: a reference expert group of five consultant radiologists, four radiology registrars, five senior house officers, and six interns. Each of the four clinician groups is known to have significantly different performance in the identification of pneumothoraces in chest x-ray. Each of the 20 participants was shown 6 nonradiologic images (3 maps and 3 sets of geometric shapes) and was asked to perform search tasks. Eye movements were recorded with a Tobii TX300 (Tobii Technology, Stockholm, Sweden) eye tracker. Four eye-tracking metrics were analyzed. Variables were compared to identify any differences among the groups. All data were compared by using nonparametric methods of analysis. The average number of targets identified in the maps did not change among groups [mean=5.8 of 6 targets (range 5.6 to 6 p=0.861)]. None of the four eye-tracking metrics investigated varied with experience in either search task (p>0.5). Despite clear differences in radiologic experience, these clinician groups showed no difference in nonradiologic search pattern behavior or skill across complex images. This is another viewpoint adding to the evidence that radiologic image interpretation is a learned skill and is task specific. <s> BIB079 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Not everyone is equally well suited for every endeavor—individuals differ in their strengths and weaknesses, which makes some people better at performing some tasks than others. As such, it might b... <s> BIB080 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Displays of eye movements may convey information about cognitive processes but require interpretation. We investigated whether participants were able to interpret displays of their own or others' eye movements. In Experiments 1 and 2, participants observed an image under three different viewing instructions. Then they were shown static or dynamic gaze displays and had to judge whether it was their own or someone else's eye movements and what instruction was reflected. Participants were capable of recognizing the instruction reflected in their own and someone else's gaze display. Instruction recognition was better for dynamic displays, and only this condition yielded above chance performance in recognizing the display as one's own or another person's (Experiments 1 and 2). Experiment 3 revealed that order information in the gaze displays facilitated instruction recognition when transitions between fixated regions distinguish one viewing instruction from another. Implications of these findings are discussed. <s> BIB081 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> ABSTRACTEye movements bring new information into our visual system. The selection of each fixation is the result of a complex interplay of image features, task goals, and biases in motor control and perception. To what extent are we aware of the selection of saccades and their consequences? Here we use a converging methods approach to answer this question in three diverse experiments. In Experiment 1, participants were directed to find a target in a scene by a verbal description of it. We then presented the path the eyes took together with those of another participant. Participants could only identify their own path when the comparison scanpath was searching for a different target. In Experiment 2, participants viewed a scene for three seconds and then named objects from the scene. When asked whether they had looked directly at a given object, participants’ responses were primarily determined by whether or not the object had been named, and not by whether it had been fixated. In Experiment 3, participants... <s> BIB082 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> As a promising imaging modality, digital breast tomosynthesis (DBT) leads to better diagnostic performance than traditional full-field digital mammograms (FFDM) alone. DBT allows different planes of the breast to be visualized, reducing occlusion from overlapping tissue. Although DBT is gaining popularity, best practices for search strategies in this medium are unclear. Eye tracking allowed us to describe search patterns adopted by radiologists searching DBT and FFDM images. Eleven radiologists examined eight DBT and FFDM cases. Observers marked suspicious masses with mouse clicks. Eye position was recorded at 1000 Hz and was coregistered with slice/depth plane as the radiologist scrolled through the DBT images, allowing a 3-D representation of eye position. Hit rate for masses was higher for tomography cases than 2-D cases and DBT led to lower false positive rates. However, search duration was much longer for DBT cases than FFDM. DBT was associated with longer fixations but similar saccadic amplitude compared with FFDM. When comparing radiologists’ eye movements to a previous study, which tracked eye movements as radiologists read chest CT, we found DBT viewers did not align with previously identified “driller” or “scanner” strategies, although their search strategy most closely aligns with a type of vigorous drilling strategy. <s> BIB083 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Suppose you go to the supermarket with a shopping list of 10 items held in memory. Your shopping expedition can be seen as a combination of visual search and memory search. This is known as "hybrid search." There is a growing interest in understanding how hybrid search tasks are accomplished. We used eye tracking to examine how manipulating the number of possible targets (the memory set size [MSS]) changes how observers (Os) search. We found that dwell time on each distractor increased with MSS, suggesting a memory search was being executed each time a new distractor was fixated. Meanwhile, although the rate of refixation increased with MSS, it was not nearly enough to suggest a strategy that involves repeatedly searching visual space for subgroups of the target set. These data provide a clear demonstration that hybrid search tasks are carried out via a "one visual search, many memory searches" heuristic in which Os examine items in the visual array once with a very low rate of refixations. For each item selected, Os activate a memory search that produces logarithmic response time increases with increased MSS. Furthermore, the percentage of distractors fixated was strongly modulated by the MSS: More items in the MSS led to a higher percentage of fixated distractors. Searching for more potential targets appears to significantly alter how Os approach the task, ultimately resulting in more eye movements and longer response times. <s> BIB084 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> PURPOSE ::: To explore the characteristics that impact lung nodule detection by peripheral vision when searching for lung nodules on chest CT-scans. ::: ::: ::: METHODS ::: This study was approved by the local IRB and is HIPAA compliant. A simulated primary (1°) target mass (2 × 2 × 5 cm) was embedded into 5 cm thick subvolumes (SV) extracted from three unenhanced lung MDCT scans (64 row, 1.25 mm thickness, 0.7 mm increment). One of 30 solid, secondary nodules with either 3-4 mm and 5-8 mm diameters were embedded into 192 of 207 SVs. The secondary nodule was placed at a random depth within each SV, a transverse distance of 2.5, 5, 7.5, or 10 mm, and along one of eight rays cast every 45° from the center of the 1° mass. Video recordings of transverse paging in cranio-caudal direction were created for each SV (frame rate three sections/sec). Six radiologists observed each cine-loop once while gaze-tracking hardware assured that gaze was centered on the 1° mass. Each radiologist assigned a confidence rating (0-5) to the detection of a secondary nodule and indicated its location. Detection sensitivity was analyzed relative to secondary nodule size, transverse distance, radial orientation, and lung complexity. Lung complexity was characterized by the number of particles (connected pixels) and the sum of the area of all particles above a -500 HU threshold within regions of interest around the 1° mass and secondary nodule. ::: ::: ::: RESULTS ::: Using a proportional odds logistic regression model and eliminating redundant predictors, models fit individually to each reader resulted in the following decreasing order of association based on greatest reduction in Akaike Information Criterion: secondary nodule diameter (6/6 readers, P < 0.001), distance from central mass (6/6 readers, P < 0.001), lung complexity particle count (5/6 readers, P = 0.05), and lung complexity particle area (3/6 readers, P = 0.03). Substantial inter-reader differences in sensitivity to decreasing nodule diameter, distance, and complexity characteristics were observed. ::: ::: ::: CONCLUSIONS ::: Of the investigated parameters, secondary nodule size, distance from the gaze center and lung complexity (particle number and area) significantly impact nodule detection with peripheral vision. <s> BIB085 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> The interpretation of chest radiographs is a complex task that is prone to diagnostic error, especially for medical students. The aim of this study is to investigate the extent to which medical students benefit from the use of a checklist regarding the detection of abnormalities on a chest radiograph. We developed a checklist based on literature and interviews with experienced thorax radiologists. Forty medical students in the clinical phase assessed 18 chest radiographs during a computer test, either with (n = 20) or without (n = 20) the checklist. We measured performance and asked participants for feedback using a survey. Participants that used a checklist detected more abnormalities on images with multiple abnormalities (M = 50.1%) than participants that could not use a checklist (M = 41.9%), p = 0.04. The post-experimental survey shows that on average, participants considered the checklist helpful (M = 3.25 on a five-point scale), but also time consuming (M = 3.30 on a five-point scale). In conclusion, a checklist can help medical students to detect abnormalities in chest radiographs. Moreover, students tend to appreciate the use of a checklist as a helpful tool during the interpretation of a chest radiograph. Therefore, a checklist is a potentially important tool to improve radiology education in the medical curriculum. <s> BIB086 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Three dimensional image modalities introduce a new paradigm for visual search requiring visual exploration of a larger search space than 2D imaging modalities. The large number of slices in the 3D volumes and the limited reading times make it difficult for radiologists to explore thoroughly by fixating with their high resolution fovea on all regions of each slice. Thus, for 3D images, observers must rely much more on their visual periphery (points away from fixation) to process image information. We previously found a dissociation in signal detectability between 2D and 3D search tasks for small signals in synthetic textures evaluated with non-radiologist trained observers. Here, we extend our evaluation to more clinically realistic backgrounds and radiologist observers. We studied the detectability of simulated microcalcifications (MCALC) and masses (MASS) in Digital Breast Tomosynthesis (DBT) utilizing virtual breast phantoms. We compared the lesion detectability of 8 radiologists during free search in 3D DBT and a 2D single-slice DBT (center slice of the 3D DBT). Our results show that the detectability of the microcalcification degrades significantly in 3D DBT with respect to the 2D single-slice DBT. On the other hand, the detectability for masses does not show this behavior and its detectability is not significantly different. The large deterioration of the 3D detectability of microcalcifications relative to masses may be related to the peripheral processing given the high number of cases in which the microcalcification was missed and the high number of search errors. Together, the results extend previous findings with synthetic textures and highlight how search in 3D images is distinct from 2D search as a consequence of the interaction between search strategies and the visibility of signals in the visual periphery. <s> BIB087 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Purpose The aim of this pilot study was to assess the clinical feasibility, diagnostic yield, advantages and disadvantages of structured reporting for routine MRI-reading in patients with primary diagnosis of intracranial tumors as compared to traditional neuroradiological free text reporting. Methods A structured MRI reporting template was developed covering pathological, anatomical and functional aspects in an itemized fashion. Retrospectively 60 consecutive patients with first diagnosis of an intracranial tumor were selected from the RIS / PACS system. Structured reporting was performed by a senior neuroradiologist, blinded to clinical and radiological data. Reporting times were measured per patient. The diagnostic content was compared to free text reporting which was independently performed on the same MRI exams by two other neuroradiologists. The comparisons were categorized per item as: « congruent », « partially congruent », « incongruent » or « not mentioned in free-style report ». Results Tumor-related items: Congruent findings were found for all items (17/17) with congruence rates ranging between 98% and 39% per item. Four items achieved congruence rates ≥90%, 5 items > 80% and 9 items ≥ 70%. Partially congruent findings were found for all items in up to 50% per item. Incongruent findings were present in 7/17 items in up to 5% per item. Free text reports did not mention 12 of 17 items (range 7-43% per item). Non tumor-related items including brain atrophy, microangiopathy, vascular pathologies and various extracranial pathologies, which were not mentioned in free-text reports between 18-85% per item. Mean reporting time for structured reporting was 7:49 minutes (3:12-17:06 min). Conclusions First results showed that expert structured reporting ensured reliable detection of all relevant brain pathologies along with reproducible documentation of all predefined diagnostic items, which was not always the case for free text reporting. A mean reporting time of 8 minutes per patient seems clinically feasible. <s> BIB088 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Abstract. What are the costs and consequences of interruptions during diagnostic radiology? The cognitive psychology literature suggests that interruptions lead to an array of negative consequences that could hurt patient outcomes and lead to lower patient throughput. Meanwhile, observational studies have both noted a strikingly high rate of interruptions and rising number of interruptions faced by radiologists. There is some observational evidence that more interruptions could lead to worse patient outcomes: Balint et al. (2014) found that the shifts with more telephone calls received in the reading room were associated with more discrepant calls. The purpose of the current study was to use an experimental manipulation to precisely quantify the costs of two different types of interruption: telephone interruption and an interpersonal interruption. We found that the first telephone interruption led to a significant increase in time spent on the case, but there was no effect on diagnostic accuracy. Eye-tracking revealed that interruptions strongly influenced where the radiologists looked: they tended to spend more time looking at dictation screens and less on medical images immediately after interruption. Our results demonstrate that while radiologists’ eye movements are reliably influenced by interruptions, the behavioral consequences were relatively mild, suggesting effective compensatory mechanisms. <s> BIB089 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Image Coverage Global processing ability Learned scene regularities <s> Rummage search is the visual and haptic search of complex environments for targets. In this study, rummage search was explored using a novel analytic framework with expert dyads and novice dyads, as well as novice individuals. Participants sought an unknown number of targets placed in four rooms of a residential house. Some targets were plainly visible whereas others were hidden, and could only be found through haptic examination. Expert dyads were very good at the task, conducting a slowed, double-checking exhaustive search, while novices both failed to fixate potential target locations, and failed to carry out the appropriate action required to search those locations exhaustively. The novice dyads examined more than the novice individuals, but became more superficial in their search. We conclude that effective rummage searching is a skill enhanced by training. <s> BIB090
Image coverage should be summed across each slice in the volume, which can be accomplished by co-registering the position in depth with each eye-tracking sample. pathologists at all levels of experience were likely to select informative areas for the locations they would like to magnify, more experienced pathologists spent less time evaluating regions that ultimately would not be selected for magnification. This evidence, in addition to a number of critical behavioral and eyetracking measures, suggests that experienced pathologists have an increased ability to rapidly extract the most important information from medical images. Other studies have highlighted the similarities in search strategies between digital pathology and volumetric imaging BIB075 , but it is largely unclear how these findings relate to expertise in either domain. In addition, there are clear differences between these images: choosing to view a visible part of the image at a greater resolution is not the same as scrolling to reveal visual information that is embedded throughout the depth of the image. We believe there are a number of promising areas for future research related to how search behaviors might differ in relation to expertise across a wide variety of areas (e.g., pathology, ultrasonography). When discussing changes in search strategy with expertise, an important caveat should be considered: differences in search patterns between experts and novices do not necessarily mean that training the novice to use those strategies will improve performance. In many cases, the research indicates that strengthening the target template through greater exposure to examples of normal and abnormal images would be far more beneficial to the novice than instructing them where to look BIB076 BIB048 BIB002 BIB031 BIB013 BIB017 . Although it is tempting to identify shortcuts to expertise, most efforts to train novices to utilize new strategies or to follow the scan paths of experts have had modest success or limited generalizability (Gegenfurtner, Lehtinen, Jarodska, & Saljo, 2017;  BIB042 BIB039 BIB077 . When considering this issue, it may be helpful to consider which aspects of visual search might be enhanced by using these techniques. Training novices to mimic the search behavior of experts might improve overall search strategy, but it is doubtful these methods would substantially improve global processing ability, which is considered a hallmark of expertise. Rather, global processing ability is attributed to a greater ability to rapidly detect statistical abnormalities in an image via strong mental representations, which is acquired through extensive experience. Notably, expert radiologists search different areas of the image on each case, which is thought to be driven by the global properties of each image BIB028 . However, trained radiographers tend to skip the same regions consistently, which likely reflects a strategy more influenced by the prior probabilities of encountering an abnormality at a given location BIB028 . These findings suggest that although both experts and novices rely on their previous experiences to guide search, experts have stronger mental representations to rely on than novices. Future research that seeks better training techniques should consider which elements of expertise require experience and which are learned strategies. In addition, it may be beneficial to focus on supporting radiologists at different stages of development rather than seeking shortcuts between them. In addition to group-level differences between experts and novices, it may be equally beneficial to explore how idiosyncrasies in eye-movements relate to the substantial variability in performance observed among experts. BIB078 found that variations in scan patterns explain a large portion of the variance in individuals' working memory capacity, speed of processing, and intelligence. Moreover, individual differences in scan patterns seem to be fairly stable across different types of tasks, even when adopting a rigid scan pattern may not be optimal BIB018 BIB059 BIB060 BIB061 BIB049 BIB034 . In addition, scan patterns reveal a great deal about an individual's search strategy, such as a preference for speed or accuracy BIB014 . Many researchers have attempted to determine if there are domain general cognitive abilities associated with expertise in radiology, which may help predict who might become a better radiologist or explain why equal experience does not lead to equivalent performance. These approaches have largely been unsuccessful and paint a compelling picture of domain specificity with expertise BIB050  BIB079 BIB062 BIB010 BIB015 . However, performance on the first trial of a visual search task predicts which individuals will perform well with experience, which suggests there may be important individual characteristics that have been overlooked in previous research BIB080 . Research from the basic science literature suggests that differences in eye-movements may provide insight on these questions, but this has not yet been evaluated in the literature. What are the consequences of limited memory in volumetric image search? Guided search posits that attention will be directed to the subset of items in your environment that are more likely to be your target. For example, if you are searching for romaine lettuce in the grocery store, attending to green items reduces the overall number of items that need to be evaluated. However, it stands to reason that visual search would be most efficient if the cognitive system kept track of which green items have already been evaluated in order to guide attention to novel locations and minimize unintentional eye-movements to previously visited locations. Such a mechanism would be particularly advantageous for professional visual searchers, such as radiologists, who need to efficiently determine which areas of large volumetric images they have already evaluated and when it is time to move on to another task. Many models of visual search carry the implicit assumption that previously attended objects will never be reevaluated (e.g., BIB005 . Consistent with this assumption, research has shown that observers search as if they have implicit memory about where they have recently looked: saccades are more likely to move in the same direction as the preceding saccade than the opposite direction BIB019 , saccadic latency is higher to previously visited locations than to novel locations BIB008 , and refixation rate more closely resembles a model that assumes memory of previous fixations than one that does not BIB046 BIB025 . A commonly proposed mechanism for this phenomenon is inhibition of return (IOR), which is a term used to describe delayed response times to probes in recently attended locations relative to novel locations  . In real-world search tasks, IOR is thought to serve as a foraging facilitator BIB019 . In support of this hypothesis, BIB019 found that saccades to a probe in a Where's Waldo search task were delayed in recently (2-3 back) fixated locations. However, despite the obvious utility of a memory mechanism in visual search, evidence for it has been surprisingly mixed. BIB016 found that search efficiency was not affected when objects moved around in the scene every 100 ms, which suggests that memory typically plays little to no role in visual search. This extreme model of a memoryless search has been challenged many times (e.g., BIB035 BIB021 BIB025 BIB022 , but these results do indicate that visual search may involve less memory for previously visited locations than our intuition suggests. One proposal that attempts to reconcile these conflicting pieces of evidence is that IOR serves to discourage perseveration in visual search, but is too limited in capacity (~4 items) and takes too long to develop (~200-300 ms) to produce a search that "samples without replacement" BIB029 . These limitations also cast doubt on the idea that IOR might play a substantial role when scrolling through large, volumetric medical images that necessitate hundreds of fixations. Furthermore, IOR appears to be severely disrupted by interruptions, particularly when the search array is no longer visible BIB023 . This suggests that IOR may be closely tied to objects in the scene rather than spatial location. If IOR is only effective when tagged objects are visible, moving to new layers of depth may disrupt the process and further limit the utility of an IOR mechanism in volumetric image search. It appears that implicit memory for previously viewed locations is fairly limited, but what about explicit memory? When searching a complex scene (e.g., Where's Waldo) observers are able to distinguish their own eyemovements from randomly generated scan paths Kingstone, 2013a, 2013b; BIB071 . However, observers are close to chance at distinguishing their own fixations from a stranger's fixations, particularly in static displays Kingstone, 2013a, 2013b; BIB081 BIB071 . One explanation for this pattern of results is that observers rely on their knowledge of where it would make the most sense to look in an image to perform the task rather than maintain a representation of their scan path in memory BIB051 BIB052 BIB071 . In further support of this view, observers are able to better discriminate their own eye-movements in a given scene when the second observer searched for a different item and over-represent the likelihood that objects that are easily accessible in memory were fixated on during visual search BIB082 . Together, these results point to surprisingly poor explicit memory for previously visited locations, which is primarily driven by informed guesses about where someone should have looked in a scene rather than memory per se. What implications do poor implicit and explicit memory have for radiologists searching through volumetric images? If you forget where you have searched for your keys in the morning, the worst-case scenario is that you are a few minutes late for work because you checked the same places more than once. However, it would be highly consequential for a radiologist to forget whether or not they have checked everywhere for signs of trauma after a car accident. This may be particularly relevant for volumetric images: it may be more difficult to maintain a representation of where you have already searched when images increase in size. Furthermore, it is more time consuming to start over or retrace your steps in a large CT scan than in a radiograph if you lose your place, which is even more consequential in light of the increase in radiologists' workload due to volumetric imaging BIB044 BIB066 . The visual search literature suggests that knowledge of where you have already searched is largely based on statistical regularities and scene context BIB020 BIB082 BIB026 . There is little reason to suspect that expert radiologists would differ in this finding, but there are clear limitations to this strategy. For example, following an interruption, where does the radiologist choose to resume their search? One possibility is that radiologists have forgotten where they have already searched and unknowingly revisit those locations, which could be observed by tracking the number of refixations and the accuracy of search resumption following the interruption  . However, from these measures alone, it is unclear if areas are revisited because they are forgotten or if they are consciously revisiting these areas in order to better recall what they intended to do next. This limitation highlights the need for more direct measures of memory in applied visual search tasks. If explicit recall is largely based on knowledge of which areas should be searched rather than knowledge of where you have actually searched, this strategy may lead to inaccurate search resumption following an interruption. One possibility is that relevant areas will be prioritized and more resistant to the effects of interruptions. Alternatively, if memory recall is primarily based on which areas should be searched, the most relevant structures might be recalled despite the fact that they were never searched. One way to disentangle these possibilities would be to combine indirect measures (e.g., eye-tracking) with more direct measures (e.g., periodic probes) to determine which areas are more likely to be reported as searched following an interruption. Consistent with a poor memory account, radiologists often search a surprisingly small portion of medical images, even though coverage is negatively associated with error rate within an expert population BIB067 BIB001 . For example, found that only 69% of the lung was searched during lung cancer screening using a 5°useful field of view (UFOV) estimate. Drillers covered more of the image than scanners, which may be another factor that explains their better performance. Using a smaller UFOV (2.6°of visual angle), BIB067 found that average coverage for lung cancer screening was only 26.7%. Consistent with research using 2D images, higher coverage was associated with reduced sensitivity. In fact, they estimate it would have taken almost 12 min per case for the images to be thoroughly searched, but average search time was closer to 3 min. In a direct comparison between 2D and volumetric image search, coverage was higher for mammography than breast tomosynthesis over a wide range of UFOV estimates BIB083 . In fact, overall coverage was less than 30% in volumetric images using the highest UFOV estimate (5°). A similar finding of decreased volumetric image coverage was observed in a study comparing DBT to single-slice DBT BIB087 . Although it is clear that coverage is low in volumetric images, it is impossible to obtain a precise estimate of coverage without an accurate UFOV estimate (Fig. 5) . In chest radiography, 5°is a common estimate of UFOV because the vast majority of lung nodules can be detected within that window BIB009 . However, UFOV is known to decrease with image complexity and task difficulty BIB084 BIB053 , and research suggests this estimate may be too generous for lung cancer screening in chest CT . It is also important to note that UFOV varies substantially with nodule size, image complexity, and reader BIB085 . In future research, it may be necessary to empirically validate UFOV estimates for a particular task or to report results for a range of UFOV estimates (e.g., BIB083 . For example, BIB067 calculated UFOV based on the distance of nodules from central fixation at the moment of recognition, and found that 99.8% of detected nodules were 50 pixels or less from central fixation (2.6°window). Notably, 25% of missed nodules were never within UFOV, which highlights the potential consequences of poor image coverage in large volumetric images. In addition, it is important to understand how UFOV changes as a function of expertise in order to test models of expertise in volumetric images. For example, if experts are able to detect abnormalities more effectively using parafoveal vision, they should have a wider UFOV than novices. In light of the poor image coverage associated with volumetric images, holistic processing might play a downsized role relative to overall image coverage: it is obvious there could be no behavioral benefit if the slices of the image that contain the abnormality are never visible. For example, there may be a behavioral cost of expertise if there are unexpected abnormalities in an image. We know that contextual cueing is detrimental to performance if the target is not in the expected location BIB043 . Similarly, in medical images, initially incorrect holistic decisions are rarely reverted BIB041 ) and clinical history Williams and Drew Cognitive Research: Principles and Implications (2019) significantly affects how images are interpreted  . In volumetric images, these effects may be exacerbated by the increased need to reduce the overall search area and the ability to scroll directly to regions of interest. For example, the most logical way for a radiologist to evaluate a patient for gallstones is to focus on the layers of the image where the gallbladder is present. However, this approach may lead to negative consequences if there are unexpected abnormalities, such as cancer, that are visible on different slices of the image. Although missed incidental findings are not necessarily an error in the context of the assigned task, the undetected cancer may nonetheless result in negative patient outcomes and/or medical malpractice claims. Considering the potential for incomplete image coverage to result in negative consequences for both the patient and the radiologist, future research on this topic is essential. Given the limitations of memory in search, it is reasonable to question how attention is guided to new locations at all in volumetric images. Eye-tracking during real-world tasks suggests that humans continually sample their environment for information rather than relying on short-term memory BIB012 . In fact, some researchers have suggested that the appearance of mnemonic mechanisms in visual search may be driven largely by search strategies rather than memory for previously searched locations BIB036 . Observers often adopt a systematic pattern during orderly visual search tasks and display a bias toward horizontal scans of the scene BIB037 BIB032 BIB033 . Furthermore, working memory capacity (~4 items;  ) is typically assumed to be a limiting factor for the number of previous locations that can be maintained in memory BIB030 . However, some studies have found that observers are less likely to refixate on as many as 12 previous fixations and will report with high confidence whether or not a target appeared at those locations BIB037 BIB036 . Working memory capacity limitations may be overcome by maintaining a coarse representation of the general search path rather than a high-resolution memory of the distractor locations BIB037 BIB054 BIB036 . Notably, random deployments of attention to salient stimuli are faster than volitional deployments of attention, which may explain why observers often fail to engage in a systematic search pattern BIB024 . This research suggests it is often a better strategy to randomly sort through large amounts of visual information quickly rather than perform slow systematic searches of the environment. However, it could reasonably be argued that a systematic strategy should play a larger role in radiology due to the need to prioritize accuracy over speed in medicine. Nonetheless, BIB009 calculated that a systematic search strategy through a chest radiograph would require 500 fixations and 3 min of searching, which far exceeds what is typically observed in these tasks (e.g., 1 min, 50 s by expert observers in BIB007 . Thus, it seems that radiologists often adopt search strategies that prioritize efficiency over an exhaustive search. Nonetheless, the sheer size of volumetric images may necessitate some degree of systematic search through the depth of the image in order to counteract a limited memory system. In support of this proposal,  found that partitioning a search array Fig. 5 How useful field of view (UFOV) is defined (in terms of degrees of visual angle (dva)) directly influences the outcome of downstream analyses, such as error classification and image coverage. In this hypothetical example, an observer fixated three times (represented by concentric circles) on an image with a visible lung-nodule (located in the red box) but failed to report it. Using a smaller UFOV, the missed abnormality would be considered a search error. However, it would be classified as a recognition or decision error using the largest UFOV estimate. Similarly, estimated image coverage varies considerably with UFOV size. Critically, the size of the UFOV is both task-dependent and observer-dependent BIB084 BIB053 BIB085 Williams and encouraged a more systematic search strategy and led to improvements in explicit recall for previous target locations. Similarly, expert dermatologists exhibited fewer refixations that were separated further in time and were less likely to retrace a scan path than novices BIB072 . In addition, there is compelling evidence in other areas of radiology that using a more structured approach might generally help offset memory demands and improve performance. For example, relative to free-form dictation templates, structured templates improve dictation quality BIB068 BIB063 BIB045 , encourage adherence to best practices BIB055 , and improve diagnostic accuracy BIB088 BIB064 BIB069 WildmanTobriner et al., 2017) . Similarly, using a checklist with anatomical structures and frequently missed diagnoses improved diagnostic performance in a group of medical students BIB086 , though see Berbaum, Franken Jr., Caldwell, & Schwartz, 2006 . In addition, radiologists tend to look at their dictation screens more often following an interruption, presumably in order to remember where they have already searched BIB089 . Together, this evidence suggests that interventions that target memory limitations are a worthwhile endeavor, but it is not yet known if adopting a systematic search strategy might also help counteract these limitations in volumetric search. How do radiologists decide to terminate search in large volumetric images? Another challenge for our limited memory in visual search is determining when to stop searching and move on to the next task. In some cases, the answer is simple. If you are looking for honeycrisp apples in a new grocery store, you will stop searching once you have found them. However, how do you know when to stop searching if the store does not sell these apples? In radiology, the problem becomes even more complex; the targets are often unspecified in both appearance and quantity. If the radiologist finds a tumor, there may still be other tumors located elsewhere. The most conservative approach would be to search every relevant pixel of the image. However, time-constraints likely prohibit such a strategy, particularly in light of the increase in the size and number of images generated by volumetric imaging techniques in recent years BIB066 . Furthermore, even if the radiologist has an unlimited amount of time to conduct such a search, a failure to find an abnormality does not mean that an abnormality is not there. In fact, many abnormalities in radiology are fixated on but never reported BIB004 . So how does the radiologist decide when to terminate search given all of this uncertainty? A model of search termination has been proposed that is similar to a drift diffusion model BIB047 . During search, information is acquired about how long or how many items you have searched until a termination threshold is reached. This threshold can be pushed around by variables in your environment, such as the likelihood of a target being present or the reward associated with finding the target. Recently, it has been proposed that search termination may mimic foraging behavior observed in the wild  BIB056 . When an animal forages for food, such as berries, energy intake is maximized by moving on to the next bush when the intake falls below the average intake for that environment, which is known as optimal foraging theory BIB003 . Observers seem to follow the predictions of this model when searching for multiple targets, and collect items in runs of one target at a time when searching for multiple different types of targets  BIB056 BIB073 . However, it is less clear how quitting behavior changes when the goal is not to collect a large number of abundant, obvious targets but instead to find rare, hard-to-find targets. Although terminating search too early may lead to negative consequences in radiology, the factors that determine when a radiologist decides to terminate search are poorly understood. Existing models of medical image interpretation focus on what might be considered the front-end of the clinician's ultimate task of accurate diagnosis: initial perception BIB006 . It is important to note that these models do little to account for the decisionmaking that follows perception. This is in contrast to a number of cognitive models, such as a class of driftdiffusion models, that were explicitly designed to account for differences in how long it takes for an observer to reach a decision (e.g., BIB040 . None of the current models of medical image perception address how a clinician ultimately decides when to stop examining a case. However, it is clear that most true positives are identified very early during search BIB011 BIB007 BIB027 ) and large portions of CT scans are never searched at all (e.g., BIB067 . As search continues, the likelihood of false positives increases dramatically. This topic is particularly important in the context of volumetric images, which typically take much longer to evaluate than 2D images. Under these circumstances, ability to efficiently move on from a healthy patient's scans may be a critical indicator of expertise that would be missed by the existing models. For example, in 2D images, experienced radiologists appear to terminate their search when they are still identifying more true positives than false positives, but novices continue until false positives are the dominant response BIB007 BIB027 . Evaluating the time-course of errors with expertise in volumetric imaging is completely uncharted territory and will likely be a fruitful area for future research. In addition, future research could seek to apply a drift diffusion modeling technique to determine how different factors, such as overall workload or the experience of the observer, influence the quitting threshold in volumetric image search. How do motor and perceptual processes interact in the evaluation of volumetric images? Unlike the feature-based searches that are common in the literature on visual attention, search in the real world often involves navigating through large 3D spaces for objects that may be obscured by other objects. When searching a field for targets, participants spontaneously adopt a systematic search path  . Similarly, when searching for evidence of a crime, participant dyads engage in a highly systematic search and frequently double check their work BIB090 . However, others have found that revisits are rare in realworld visual search, which is attributed to the extra effort required to retrace your steps in locomotive tasks  BIB038 . Together, this research has profound implications for volumetric image search, which involves both motor and perceptual components as the observer scrolls through depth. In recent years, there has been a growing interest in how motor processes influence visual search when target items must be located by moving other items, termed "manually assisted search." In some cases, manually assisted search has replicated findings from the visual search literature (e.g., "the low prevalence effect", BIB065 . In other cases, new sources of error have been identified. For example, Solman, Cheyne, and Smilek (2012) created an "unpacking" paradigm where the observer could move overlapping virtual items using the computer mouse. The researchers found that target items were often picked up and discarded without being recognized, which suggests that perception and action can be decoupled in visual search. In other words, a decision for action ("discard the selected item") can precede a decision for identification ("the selected item is my target"). The authors propose that naturalistic visual search engages a perceptual search process that supervises, but does not direct, the motor "unpacking" process BIB057 . In radiology, the findings could mean that the motor system decides to move through depth before an abnormality can be identified on the current slice. Although verbal instructions to slow down motor movements were ineffective, forcing the participant to slow down significantly reduced unpacking errors BIB057 . At present, it is unknown how the speed of scrolling through the depth of a volumetric medical image relates to diagnostic accuracy or whether these "decoupling" errors occur in radiology. Presenting CT scans at different frame rates has led to mixed outcomes, ranging from no accuracy differences BIB058 to poorer performance at faster speeds BIB074 . Scrolling speed may also provide insight on the effectiveness of motion onset cues or the development of global processing ability in volumetric imaging. If experts are able to extract relevant information from the images more quickly than novices, they might be less vulnerable to the potentially negative effects of scrolling more quickly, such as "decoupling" errors. In a lung cancer screening task, there were no observed differences in speed between radiologists and naïve observers BIB070 . On average, nodules were detected at a speed between 25 and 30 frames per second (fps). However, it is notable that performance in this task was at ceiling for both experts and novices, and there were no differences in performance across groups. Therefore, it remains possible that differences in scrolling behavior are more important when there is greater variability in performance. BIB058 also found no expertise-related differences in performance when observers looked for a variety of abnormalities in abdominal CT scans presented as fixed-speed videos at 7, 14, or 28 fps. In contrast, BIB074 observed better performance at 5 fps than 3 fps, and experts were better able to adapt to the increased presentation rate in abdominal CT scans. However, both of these studies relied on fixed-speed videos rather than allowing the observers to control their own speed, which limits ecological validity. Clearly, there is not yet a complete picture of how scrolling speed influences search performance in volumetric images. In future research, it may also be beneficial to analyze the distribution of errors as a function of naturalistic scrolling speed. Moreover, it is important to consider the properties of the abnormality itself. Scrolling speed might be an important predictor of abnormality detection when abnormalities elicit motion onset cues or for smaller abnormalities that are visible on fewer layers of depth. In contrast, it is less likely that scrolling speed predicts the detectability of diffuse or large abnormalities that are visible throughout many slices.