What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> The process of roentgen diagnosis comprises three basic steps: the recording, the perception, and the interpretation of critical roentgen shadows. Volumes have been written on the recording and interpretation of these shadows, but their perception is so spontaneous that radiologists have largely taken it for granted. Errors can and do arise in this stage of roentgen diagnosis, however, and their control depends on our knowledge of the mechanisms involved. It is our purpose here, therefore, to summarize present knowledge of visual perception as it relates to roentgen diagnosis, and to suggest new research which may shed further light on this aspect. Frequency of Perceptual Error We fail to perceive significant findings in the roentgenogram with surprising frequency. With several colleagues, I investigated this problem some years ago and was amazed to find that three experienced radiologists, charged only with indicating the presence of abnormal shadows3 in a collection of chest films, “overlooked” 20 to 30... <s> BIB001 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB002 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Detection of lung nodules contained in chest X-ray films was studied during both tachistoscopic presentation and free search. Lung nodules were first rated for their visibility against the anatomical background of the chest films. With tachistoscopic presentation, detection accuracy was influenced by rated visibility and by exposure durations up to 180 msec. Eye movements and fixations were recorded during free search. These measures indicated that radiologists use a comparative scanning strategy to differentiate nodules from anatomical structures. The frequency of comparative scans was influenced by rated visibility: Less visible nodules received more comparisons than the more visible nodules. We believe that the radiologist compares suspected nodules with the features of normal structures which serve as references for decisions. <s> BIB003 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Yantis and Jonides (1984) demonstrated that the detection of a target in visual search was markedly enhanced when the target was presented as an abruptly onset character embedded among other characters whose presentation was not characterized by abrupt onset. This effect was attributed to a shift of attention caused by abrupt onset. In the present article, we report experiments investigating whether abrupt onset is simply one member of a large class of stimulus characteristics, all of which are capable of capturing attention. To test this possibility, we compared abrupt onset with differences in stimulus luminance and hue to determine whether these also could elicit shifts of attention. They could not. <s> BIB004 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Subjects searched sets of items for targets defined by conjunctions of color and form, color and orientation, or color and size. Set size was varied and reaction times (RT) were measured. For many unpracticed subjects, the slopes of the resulting RT X Set Size functions are too shallow to be consistent with Treisman's feature integration model, which proposes serial, self-terminating search for conjunctions. Searches for triple conjunctions (Color X Size X Form) are easier than searches for standard conjunctions and can be independent of set size. A guided search model similar to Hoffman's (1979) two-stage model can account for these data. In the model, parallel processes use information about simple features to guide attention in the search for conjunctions. Triple conjunctions are found more efficiently than standard conjunctions because three parallel processes can guide attention more effectively than two. <s> BIB005 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Eye position recordings made while radiologists searched chest images for lung nodules showed that regions falsely reported positive or suspicious received prolonged visual attention. Correlation of regional fixation dwell time with independent ratings of image features indicated that more than 90% of false-positive decisions were caused by some perturbation in the image that aroused the suspicion of the viewer. The remainder apparently arose from within the viewer. Most missed nodules (false-negative reports) also received prolonged visual attention, implying an active decision not to perceive a nodule. The data are interpreted to show that roughly one task-related decision is made during each second of scanning a radiograph. This departs from the central assumption of the traditional signal-detection model based upon one decision per image. <s> BIB006 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> A subset of underreading errors (false-negative responses) in radiology has been attributed to "satisfaction of search," which occurs when lesions remain undetected after detection of an initial lesion. This phenomenon has not been studied in the experimental laboratory. A primary goal of this study was to develop a procedure or paradigm to study satisfaction of search. The authors measured detection accuracy for native lesions in images before and after the addition of a simulated nodular lesion. Simulated and native lesions were not spatially superimposed and the native abnormalities were physically identical with and without the nodules. Only responses related to the native lesion were analyzed. Accuracy parameters of receiver operating characteristic (ROC) curves were estimated by the method of maximum likelihood and jackknife. The average perceptual accuracy of the individual ROC curves as measured by Az and de' was significantly reduced with addition of the nodules (t = 2.364, p = 0.025, t = 2.648, p = 0.017, respectively). Az and de' parameters of the pooled ROC curve showed a similar effect (t = 1.573, p = 0.080; t = 1.934, p = 0.047, respectively). The results indicated a substantial satisfaction-of-search effect, with diminished accuracy in perception of native lesions. <s> BIB007 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Search for a target defined by a conjunction of movement and form (e.g., an X moving up in a display of intermingled Os moving up and stationary Xs) is parallel. This result is also found if (a) the moving Os and target X move in unpredictable directions so that the moving stimuli do not form a clear perceptual group or (b) the nontarget Xs also move but in a known, different direction from the Os and target X. In contrast, search is slow and serial if the target may be unpredictably among either moving or stationary stimuli. These results suggest that a component of the visual system operates as a movement filter that can direct attention to stimuli with a common movement characteristic. The filtering cue can be moving (vs. stationary), or movement in 1 particular direction. The results do not support the view that attention can only be directed to groups defined by common fate. <s> BIB008 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB009 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> PURPOSE: To determine radiologists' ability to find lung nodules on spiral computed tomographic (CT) scans of the chest with both rapid sequential (cine) and conventional film-based viewing. MATERIALS AND METHODS: Eight radiologists searched for lung nodules on spiral CT images (10-mm collimation, 10 mm/sec table speed) presented in two formats. Cine viewing was performed at a computer work-station; sections were viewed in 2-mm increments at frame rates up to 10 frames per second. Film-based viewing of images from a laser printer was performed with a lightbox; sections were viewed at 4-mm increments. Eight 3-5-mm-diameter simulated nodules were superimposed on each of five normal CT scans. RESULTS: Radiologists found a higher fraction of nodules with the cine presentation than with film (mean, 0.69 +/- 0.02 [standard error] versus 0.58 +/- 0.03, respectively [P = .006]). Diameter thresholds for nodule detection (50% correctly localized) were 3.3 and 3.5 mm, respectively. CONCLUSION: Cine viewing of spiral... <s> BIB010 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> We examined the ability of younger and older adults to selectively process moving items and ignore stationary items in a task that required the search for a target defined by a conjunction of movement and form (i.e., search for a moving X among moving Os and stationary Xs) in displays of 5, 9, 17, and 25 stimuli (Experiment 1) and displays of 5, 10, and 20 stimuli (Experiment 2). We also investigated subjects' performance in two feature search tasks, the search for a target defined by movement or form. Finally, we examined the influence of practice on feature and conjunction search. Younger and older adults searched the displays at similar rates in the feature and conjunction search tasks. Older and younger adults also benefited equivalently from practice. These data suggest age-equivalence in the processes which underlie feature search in dynamic environments as well as those processes responsible for the segregation of moving and stationary objects in the visual field. Language: en <s> BIB011 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Motion information tends to be segregated from color and form information in the visual system, both perceptually and neuroanatomically, and it is therefore possible that different mechanisms of attention are used to select targets defined by these different feature types during visual search. To test this hypothesis, we recorded the N2pc component of the event-related potential waveform during visual search tasks with color, orientation, and motion targets. The N2pc component has previously been shown to reflect a specific attentional mechanism that is present for color and form targets, and we sought to determine whether this component would also be present for motion targets. The N2pc component was indeed observed for motion targets as well as color and orientation targets, consistent with the use of a common attentional mechanism across feature types. In addition, we found that motion singletons (i.e., individual items that moved in the opposite direction from the other items in the army) elicited an N2pc component even when they were task-irrelevant, indicating that motion discontinuities may produce an automatic orienting of attention. <s> BIB012 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> PURPOSE ::: To compare picture archiving and communication system (PACS) image display in so-called stack mode with conventional image display, tile mode, in efficacy of analysis of three-dimensional structure on computed tomographic (CT) scans. ::: ::: ::: MATERIALS AND METHODS ::: A complex three-dimensional phantom composed of 20 entangled tubes was constructed and scanned. The resultant images were transferred to a PACS for analysis. Five experienced CT radiologists were asked to unravel the tubes by identifying their ends and to perform this task in both stack and tile modes. The time taken and any errors were recorded. ::: ::: ::: RESULTS ::: All five radiologists performed considerably faster in stack mode than in tile mode; the speed varied by a factor of 3.2-5.7 times. The results of a paired t test showed this difference to be significant (P = .0002). Furthermore, no mistakes were made in stack mode, while two mistakes were made in tile mode. ::: ::: ::: CONCLUSION ::: Stack mode facilitates analysis of three-dimensional structure depicted on CT scans. <s> BIB013 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> With each eye fixation, we experience a richly detailed visual world. Yet recent work on visual integration and change direction reveals that we are surprisingly unaware of the details of our envir... <s> BIB014 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Previous research has shown that when searching for a color singleton. top-down control cannot prevent attentional capture by an abrupt visual onset. The present research addressed whether a task-irrelevant abrupt onset would affect eye movement behavior when searching for a color singleton. Results show that in many instances the eye moved in the direction of the task-irrelevant abrupt onset. There was evidence that top-down control could neither entirely prevent attentional capture by visual onsets nor prevent the eye from starring to move in the direction of the onset. Results suggest parallel programming of 2 saccades: 1 voluntary goal-directed eye movement toward the color singleton target and 1 stimulus-driven eye movement reflexively elicited by the abrupt onset. A neurophysiologically plausible model that can account for the current findings is discussed. <s> BIB015 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> RATIONALE AND OBJECTIVES ::: The goal of the study was to determine whether there are certain physical features of pulmonary nodules that attract visual attention and contribute to increased recognition and detection by observers. ::: ::: ::: MATERIALS AND METHODS ::: A series of posteroanterior chest images with solitary pulmonary nodules were searched by six radiologists as their eye-position was recorded. The signal-to-noise ratio, size, conspicuity, location, and calcification status were measured for each nodule. Dwell parameters were correlated with nodule features and related to detection rates. ::: ::: ::: RESULTS ::: Only nodule size (F = 5.08, P = .0254) and conspicuity (F = 4.625, P = .0329) influenced total dwell time on nodules, with larger, more conspicuous nodules receiving less visual attention than smaller, less conspicuous nodules. All nodule features examined influenced overall detection performance (P < .05) even though most did not influence visual search and attention. ::: ::: ::: CONCLUSION ::: Individual nodule features do not attract attention as measured by "first hit" fixation data, but certain features do tend to hold attention once the nodule has been fixated. The combination of all features influences whether or not it is detected. <s> BIB016 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Although visual motion may seem salient, motion per se does not automatically attract attention. We show here, however, that the onset of motion does indeed attract attention. In three experiments, subjects identified target letters in displays that contained targets and distractors. There was no advantage for moving letters among static ones, but there was an advantage for objects that had recently started to move despite the fact that the motion was uninformative. If some additional time was allowed to elapse after motion onset, inhibition of return slowed responding to the item that had started to move—a further sign that the motion onset had captured attention. Finally, detection of target letters was found to be independent of the number of distractors in the display if the target had undergone motion onset, also indicative of attentional capture. We discuss the adaptive significance of sensitivity to onsets in the presence of a relative insensitivity to ongoing motion. <s> BIB017 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> The effects of mental workload on visual search and decision making were studied in real traffic conditions with 12 participants who drove an instrumented car. Mental workload was manipulated by having participants perform several mental tasks while driving. A simultaneous visual-detection and discrimination test was used as performance criteria. Mental tasks produced spatial gaze concentration and visual-detection impairment, although no tunnel vision occurred. According to ocular behavior analysis, this impairment was due to late detection and poor identification more than to response selection. Verbal acquisition tasks were innocuous compared with production tasks, and complex conversations, whether by phone or with a passenger, are dangerous for road safety. Language: en <s> BIB018 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Most laboratory visual search tasks involve many searches for the same target, while in the real world we typically change our target with each search (e.g. find the coffee cup, then the sugar). How quickly can the visual system be reconfigured to search for a new target? Here observers searched for targets specified by cues presented at different SOAs relative to the search stimulus. Search for different targets on each trial was compared to search for the same target over a block of trials. Experiments 1 and 2 showed that an exact picture cue acts within 200 ms to make varied target conjunction search as fast and efficient as blocked conjunction search. Word cues were slower and never as effective. Experiment 3 replicated this result with a task that required top-down information about target identity. Experiment 4 showed that the effects of an exact picture cue were not mandatory. Experiments 5 and 6 used pictures of real objects to cue targets by category level. <s> BIB019 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB020 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Many theories have proposed that visual working memory plays an important role in visual search. In contrast, by showing that a nonspatial working memory load did not interfere with search efficiency, Woodman, Vogel, and Luck (2001) recently proposed that the role of working memory in visual search is insignificant. However, the visual search process may interfere with spatial working memory. In the present study, a visual search task was performed concurrently with either a spatial working memory task (Experiment 1) or a nonspatial working memory task (Experiment 2). We found that the visual search process interfered with a spatial working memory load, but not with a nonspatial working memory load. These results suggest that there is a distinction between spatial and nonspatial working memory in terms of interactions with visual search tasks. These results imply that the visual search process and spatial working memory storage require the same limited-capacity mechanisms. <s> BIB021 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Four experiments explored the interrelations between working memory, attention, and eye movements. Observers had to identify a tilted line amongst vertical distractors. Each line was surrounded by a colored shape that could be precued by a matching item held in memory. Relative to a neutral baseline, in which no shapes matched the memory item, search was more efficient when the memory cue matched the shape containing the target, and it was less efficient when the cued stimulus contained a distractor. Cuing affected the shortest reaction times and the first saccade in search. The effect occurred even when the memory cue was always invalid but not when the cue did not have to be held in memory. There was also no evidence for priming effects between consecutive trials. The results suggest that there can be early, involuntary top-down directing of attention to a stimulus matching the contents of working memory. The visual field usually contains more information than the visual system can process at any given time. Attentional mechanisms are thus crucial to selection of relevant objects for further processing and, perhaps also, to inhibition of those objects that are irrelevant to current goals. How can attention be guided so as to select the appropriate visual information? Attentional guidance can occur in a bottom-up way, as when the sudden appearance of a new object or a salient stimulus change directs our attention to its location (Theeuwes & Burger, 1998; Yantis & Hillstrom, 1994). In addition, the objects with which attention is engaged can guide its deployment over the visual field. For instance, spatial attentional shifts are faster within a selected object than they are across objects (Egly, Driver, & Rafal, 1994; Lamy & Tsal, 2000). Objects can also guide attention even when object-based cuing is not valid (Soto & Blanco, 2004) and when an object’s location can <s> BIB022 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> RATIONALE AND OBJECTIVES ::: The goal of this study is to determine whether mammographic lesion subtlety influences the detection accuracy and visual search parameters of radiologists. ::: ::: ::: MATERIALS AND METHODS ::: Six radiologists searched a set of 20 mammograms with at least two lesions per image (masses and/or microcalcifications). Eye position was recorded. False-negative (FN) and true-positive (TP) decisions were correlated with lesion subtlety and visual search parameters of time to first hit, total dwell time, and number of return fixations. ::: ::: ::: RESULTS ::: Lesions with lower subtlety ratings were detected later in the search than more obvious ones (FN later than TP decisions). When subtler lesions were detected (TP), dwell time was longer than for more obvious lesions, but FN decisions received shorter total dwell. Subtler lesions, when detected (TP), received more total fixation clusters than more obvious ones, but FN decisions received fewer. ::: ::: ::: CONCLUSION ::: Subtle mammographic lesions are associated with significantly different visual search parameters than obvious lesions, explaining in part why they are missed more often. Developing tools to improve lesion visibility may improve detection. <s> BIB023 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> In 7 experiments, the authors explored whether visual attention (the ability to select relevant visual information) and visual working memory (the ability to retain relevant visual information) share the same content representations. The presence of singleton distractors interfered more strongly with a visual search task when it was accompanied by an additional memory task. Singleton distractors interfered even more when they were identical or related to the object held in memory, but only when it was difficult to verbalize the memory content. Furthermore, this content-specific interaction occurred for features that were relevant to the memory task but not for irrelevant features of the same object or for onceremembered objects that could be forgotten. Finally, memory-related distractors attracted more eye movements but did not result in longer fixations. The results demonstrate memory-driven attentional capture on the basis of content-specific representations. <s> BIB024 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> BACKGROUND ::: Lung cancer has the highest mortality-rate per cancer, with an overall 5-year survival <15%. Several non-randomized studies pointed out the high sensitivity of low dose computed tomography (LDCT) to detect early stage lung cancer. In France, Depiscan, a pilot RCT of LDCT versus chest X-ray (CXR), started on October 2002 to determine the feasibility of enrollment by general practitioners (GPs), investigations and diagnostic procedures by university hospital radiologists and multidisciplinary teams, data management by centralized clinical research assistants, and anticipate the future management of a large national trial. ::: ::: ::: METHODS ::: GPs and occupational physicians (OPs) selected and enrolled 1000 subjects in 1 year. Eligible subjects were asymptomatic males or females aged 50-75 years with a current or former cigarette smoking history of >/=15 cigarettes per day for at least 20 years (former smokers having quit <15 years prior to enrollment). Based to randomization, annual LDCT or CXR screenings were planned at baseline and annually for 2 years. ::: ::: ::: RESULTS ::: Between October 2002 and December 2004, 765 subjects were enrolled by 89 out of the 232 participating GPs and OPs. Complete clinical and imaging baseline data were available for 621 individuals out of the 765 enrolled, due to 144 noncompliant subjects who withdrew their consent. At least one nodule was detected in 152 out of 336 subjects (45.2%) in the LDCT screening, versus 21 out of 285 subjects (7.4%) in the CXR screening arm. Eight lung cancers were detected in the LDCT arm and one in the CXR arm. ::: ::: ::: DISCUSSION ::: This pilot trial allows estimating that non-calcified nodules are 10 [6.36-17.07] times more often detected from LDCT than from CXR. However enrollment by GPs was more difficult than expected with 41% active investigators and a high rate (19%) of noncompliant patients. This experience speaks to the need for a high level of GPs formation and a large, coordinated clinical research team in such a trial. ::: ::: ::: TRIAL REGISTRATION NUMBER ::: 02526. <s> BIB025 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> We investigated the processing effort during visual search and counting tasks using a pupil dilation measure. Search difficulty was manipulated by varying the number of distractors as well as the heterogeneity of the distractors. More difficult visual search resulted in more pupil dilation than did less difficult search. These results confirm a link between effort and increased pupil dilation. The pupil dilated more during the counting task than during target-absent search, even though the displays were identical, and the two tasks were matched for reaction time. The moment-to-moment dilation pattern during search suggests little effort in the early stages, but increasingly more effort towards response, whereas the counting task involved an increased initial effort, which was sustained throughout the trial. These patterns can be interpreted in terms of the differential memory load for item locations in each task. In an additional experiment, increasing the spatial memory requirements of the search evoked ... <s> BIB026 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB027 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Historically, radiology research has been dominated by chest and breast screening. Few studies have examined complex ::: interpretative tasks such as the reading of multidimensional brain CT or MRI scans. Additionally, no studies at the time ::: of writing have explored the interpretation of stroke images; from novices through to experienced practitioners using eye ::: movement analysis. Finally, there appears a lack of evidence on the clinical effects of radiology reports and their ::: influence on image appraisal and clinical diagnosis. A computer-based, eye-tracking study was designed to assess ::: diagnostic accuracy and interpretation in stroke CT and MR imagery. Eight predetermined clinical cases, five images per ::: case, were presented to participants (novices, trainee, and radiologists; n=8). The presence or absence of abnormalities ::: was rated on a five-point Likert scale and their locations reported. Half cases of the cases were accompanied by clinical ::: information; half were not, to assess the impact of information on observer performance. Results highlight differences in ::: visual search patterns amongst novice, trainee and expert observers; the most marked differences occurred between ::: novice readers and experts. Experts spent more time in challenging areas of interest (AOI) than novices and trainee, and ::: were more confident unless a lesion was large and obvious. The time to first AOI fixation differed by size, shape and ::: clarity of lesion. 'Time to lesion' dropped significantly when recognition appeared to occur between slices. The ::: influence of clinical information was minimal. <s> BIB028 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Is the sequence of eye-movements made when viewing a picture related to encoding the image into memory? The suggestion of a relationship is supported by studies that have found that scanpaths are more similar over multiple viewings of a stimulus than would be expected by chance. It has also been found that low-level visual saliency contributes to the initial formation of these scanpaths, and has lead to formation of theories such as the saliency map hypothesis. However, bottom-up processes such as these can be overridden by top-down cognitive knowledge in the form of domain proficiency. Domain specialists were asked to look at a set of photographs of real-world scenes in preparation for a memory test. Then they were given a second set of stimuli and were asked to identify the picture as old (from the previous set) or new (never seen before). Eye tracking analyses (including scanpath comparison using a string editing algorithm) revealed that saliency did influence where participants looked and in what sequence. However, this was reliably reduced when participants viewed pictures from their specialist domain. This effect is shown to be robust in a repeated viewing of the stimuli. <s> BIB029 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Institutional review board approval and signed informed consent were not needed, as medical images included in public databases were used in this study. The purpose of this study was to improve the detection of microcalcifications on mammograms and lung nodules on chest radiographs by using the dynamic cues algorithm and the motion and flickering sensitivity of the human visual system (HVS). Different sets of mammograms from the Mammographic Image Analysis Society database and chest radiographs from the Japanese Society of Radiological Technology database were presented statically, as is standard, and in a video sequence generated with the dynamic cues algorithm. Nine observers were asked to rate the presence of abnormalities with a five-point scale (1, definitely not present; 5, definitely present). The data were analyzed with receiver operating characteristic (ROC) techniques and the Dorfman-Berbaum-Metz method. The video sequence generated with the dynamic cues algorithm increased the rate of detection... <s> BIB030 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> OBJECTIVE ::: To compare the clinical performance of digital breast tomosynthesis (DBT) with that of full-field digital mammography (FFDM) in a diagnostic population. ::: ::: ::: METHODS ::: The study enrolled 200 consenting women who had at least one breast lesion discovered by mammography and/or ultrasound classified as doubtful or suspicious or probably malignant. They underwent tomosynthesis in one view [mediolateral oblique (MLO)] of both breasts at a dose comparable to that of standard screen-film mammography in two views [craniocaudal (CC) and MLO]. Images were rated by six breast radiologists using the BIRADS score. Ratings were compared with the truth established according to the standard of care and a multiple-reader multiple-case (MRMC) receiver-operating characteristic (ROC) analysis was performed. Clinical performance of DBT compared with that of FFDM was evaluated in terms of the difference between areas under ROC curves (AUCs) for BIRADS scores. ::: ::: ::: RESULTS ::: Overall clinical performance with DBT and FFDM for malignant versus all other cases was not significantly different (AUCs 0.851 vs 0.836, p = 0.645). The lower limit of the 95% CI or the difference between DBT and FFDM AUCs was -4.9%. ::: ::: ::: CONCLUSION ::: Clinical performance of tomosynthesis in one view at the same total dose as standard screen-film mammography is not inferior to digital mammography in two views. <s> BIB031 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> OBJECTIVE. The purpose of this study was to compare in a retrospective observer study the diagnostic performance of full-field digital mammography (FFDM) with that of digital breast tomosynthesis.MATERIALS AND METHODS. Eight experienced radiologists interpreted images from 125 selected examinations, 35 with verified findings of cancer and 90 with no finding of cancer. The four display conditions included FFDM alone, 11 low-dose projections, reconstructed digital breast tomosynthesis images, and a combined display mode of FFDM and digital breast tomosynthesis images. Observers rated examinations using the screening BI-RADS rating scale and the free-response receiver operating characteristic paradigm. Observer performance levels were measured as the proportion of examinations prompting recall of patients for further diagnostic evaluation. The results were presented in terms of true-positive fraction and false-positive fraction. Performance levels were compared among the acquisitions and reading modes. Time ... <s> BIB032 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> How does expertise in the analysis of particular images influence the effects of visual saliency upon attention? Expert analysts of aerial photographs and untrained viewers undertook change-detection and location memory tasks using aerial photographs with eye movements recorded throughout. Experts were more accurate in both tasks. Significant differences were also seen in the scanpaths: Untrained viewers fixated preferentially upon salient features throughout stimulus presentation whereas experts did not. However, both groups showed a strong influence of saliency in change detection and memory tasks. We interpret this apparent contradiction by: (i) assuming that the use of saliency in visual search is discretionary, and experts can use semantic information to prioritise where to fixate next; whereas, (ii) in tasks requiring spatial memory, analysis of visual saliency delivers easily acquired landmarks to reference the location of items in an image; a previously overlooked function used by expert and untrained viewers alike. Copyright © 2009 John Wiley & Sons, Ltd. Language: en <s> BIB033 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Where does one attend when viewing dynamic scenes? Research into the factors influencing gaze location during static scene viewing have reported that low-level visual features contribute very little to gaze location especially when opposed by high-level factors such as viewing task. However, the inclusion of transient features such as motion in dynamic scenes may result in a greater influence of visual features on gaze allocation and coordination of gaze across viewers. In the present study, we investigated the contribution of low- to mid-level visual features to gaze location during free-viewing of a large dataset of videos ranging in content and length. Signal detection analysis on visual features and Gaussian Mixture Models for clustering gaze was used to identify the contribution of visual features to gaze location. The results show that mid-level visual features including corners and orientations can distinguish between actual gaze locations and a randomly sampled baseline. However, temporal features such as flicker, motion, and their respective contrasts were the most predictive of gaze location. Additionally, moments in which all viewers’ gaze tightly clustered in the same location could be predicted by motion. Motion and mid-level visual features may influence gaze allocation in dynamic scenes, but it is currently unclear whether this influence is involuntary or due to correlations with higher order factors such as scene semantics. <s> BIB034 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB035 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> The aim of this study was to investigate where neurologists look when they view brain computed tomography (CT) images and to evaluate how they deploy their visual attention by comparing their gaze distribution with saliency maps. Brain CT images showing cerebrovascular accidents were presented to 12 neurologists and 12 control subjects. The subjects' ocular fixation positions were recorded using an eye-tracking device (Eyelink 1000). Heat maps were created based on the eye-fixation patterns of each group and compared between the two groups. The heat maps revealed that the areas on which control subjects frequently fixated often coincided with areas identified as outstanding in saliency maps, while the areas on which neurologists frequently fixated often did not. Dwell time in regions of interest (ROI) was likewise compared between the two groups, revealing that, although dwell time on large lesions was not different between the two groups, dwell time in clinically important areas with low salience was longer in neurologists than in controls. Therefore it appears that neurologists intentionally scan clinically important areas when reading brain CT images showing cerebrovascular accidents. Both neurologists and control subjects used the "bottom-up salience" form of visual attention, although the neurologists more effectively used the "top-down instruction" form. <s> BIB036 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Previous work has shown that distractors present in a visual search display attract attention when they match objects kept in visual working memory. It seems that maintaining an object in working memory is functionally identical to adopting an attentional set for that object. We test this conjecture by asking observers to perform a memory task as well as a visual search task (in which memory-related distractors could return), but to leave the observer uncertain as to which of these tasks would have to be completed first. This way, observers ought to more readily look for the memorized information, rather than just remember it. Memory-related distractor effects were larger than when participants knew the order of the tasks beforehand, consistent with the idea that trying to attend to something involves additional processes or representations beyond those needed for simply storing an item. <s> BIB037 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> OBJECTIVE. The purpose of this article is to compare the ability of digital breast tomosynthesis and full field digital mammography (FFDM) to detect and characterize calcifications.MATERIALS AND METHODS. One hundred paired examinations were performed utilizing FFDM and digital breast tomosynthesis. Twenty biopsy-proven cancers, 40 biopsy-proven benign calcifications, and 40 randomly selected negative screening studies were retrospectively reviewed by five radiologists in a crossed multireader multimodal observer performance study. Data collected included the presence of calcifications and forced BI-RADS scores. Receiver operator curve analysis using BI-RADS was performed.RESULTS. Overall calcification detection sensitivity was higher for FFDM (0.84% [95% CI, 0.79–0.88%]) than for digital breast tomosynthesis (0.75% [95% CI, 0.70–0.80%]). In the cancer cohort, 75 (76%) of 99 interpretations identified calcification in both modes. Of those, a BI-RADS score less than or equal to 2 was rendered in three (4%) ... <s> BIB038 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> It has been claimed that gaze control during scene viewing is largely governed by stimulus-driven, bottom-up selection mechanisms. Recent research, however, has strongly suggested that observers’ topdown control plays a dominant role in attentional prioritization in scenes. A notable exception to this strong top-down control is oculomotor capture, where visual transients in a scene draw the eyes. One way to test whether oculomotor capture during scene viewing is independent of an observer’s top-down goal setting is to reduce observers’ cognitive resource availability. In the present study, we examined whether increasing observers’ cognitive load influences the frequency and speed of oculomotor capture during scene viewing. In Experiment 1, we tested whether increasing observers’ cognitive load modulates the degree of oculomotor capture by a new object suddenly appeared in a scene. Similarly, in Experiment 2, we tested whether increasing observers’ cognitive load modulates the degree of oculomotor capture by an object’s color change. In both experiments, the degree of oculomotor capture decreased as observers’ cognitive resources were reduced. These results suggest that oculomotor capture during scene viewing is dependent on observers’ top-down selection mechanisms. <s> BIB039 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> AIM ::: To measure the change in diagnostic accuracy of conventional film-screen mammography and full-field digital mammography (FFDM) with the addition of digital breast tomosynthesis (DBT) in women recalled for assessment following routine screening. ::: ::: ::: MATERIALS AND METHODS ::: Ethics approval for the study was granted. Women recalled for assessment following routine screening with screen-film mammography were invited to participate. Participants underwent bilateral, two-view FFDM and two-view DBT. Readers scored each lesion separately for probability of malignancy on screen-film mammography, FFDM, and then DBT. The scores were compared with the presence or absence of malignancy based on the final histopathology outcome. ::: ::: ::: RESULTS ::: Seven hundred and thirty-eight women participated (93.2% recruitment rate). Following assessment 204 (26.8%) were diagnosed as malignant (147 invasive and 57 in-situ tumours), 286 (37.68%) as benign, and 269 (35.4%) as normal. The diagnostic accuracy was evaluated by using receiving operating characteristic (ROC) and measurement of area under the curve (AUC). The AUC values demonstrated a significant (p = 0.0001) improvement in the diagnostic accuracy with the addition of DBT combined with FFDM and film-screen mammography (AUC = 0.9671) when compared to FFDM plus film-screen mammography (AUC = 0.8949) and film-screen mammography alone (AUC = 0.7882). The effect was significantly greater for soft-tissue lesions [AUC was 0.9905 with the addition of DBT and AUC was 0.9201 for FFDM with film-screen mammography combined (p = 0.0001)] compared to microcalcification [with the addition of DBT (AUC = 0.7920) and for FFDM with film-screen mammography combined (AUC = 0.7843; p = 0.3182)]. ::: ::: ::: CONCLUSION ::: The addition of DBT increases the accuracy of mammography compared to FFDM and film-screen mammography combined and film-screen mammography alone in the assessment of screen-detected soft-tissue mammographic abnormalities. <s> BIB040 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Purpose A previous study demonstrated decreased diagnostic accuracy for finding fractures and decreased ability to focus on skeletal radiographs after a long working day. Skeletal radiographic examinations commonly have images that are displayed statically. The aim of this study was to investigate whether diagnostic accuracy for detecting pulmonary nodules on CT of the chest displayed dynamically would be similarly affected by fatigue. Methods Twenty-two radiologists and 22 residents were given 2 tests searching CT chest sequences for a solitary pulmonary nodule before and after a day of clinical reading. To measure search time, 10 lung CT sequences, each containing 20 consecutive sections and a single nodule, were inspected using free search and navigation. To measure diagnostic accuracy, 100 CT sequences, each with 20 sections and half with nodules, were displayed at preset scrolling speed and duration. Accuracy was measured using receiver operating characteristic curve analysis. Visual strain was measured via dark vergence, an indicator of the ability to keep the eyes focused on the display. Results Diagnostic accuracy was reduced after a day of clinical reading ( P = .0246), but search time was not affected ( P > .05). After a day of reading, dark vergence was significantly larger and more variable ( P = .0098), reflecting higher levels of visual strain, and subjective ratings of fatigue were also higher. Conclusions After their usual workday, radiologists experience increased fatigue and decreased diagnostic accuracy for detecting pulmonary nodules on CT. Effects of fatigue may be mitigated by active interaction with the display. <s> BIB041 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Summary ::: ::: Models of expertise differences in radiology often do not take into account visual differences between diseases. This study investigates the bottom-up effects of three types of images on viewing patterns of students, residents and radiologists: focal diseases (localized abnormality), diffuse diseases (distributed abnormality) and images showing no abnormalities (normal). Participants inspected conventional chest radiographs while their eye movements were recorded. Regardless of expertise, in focal diseases, participants fixated relatively long at specific locations, whereas in diffuse diseases, fixations were more dispersed and shorter. Moreover, for students, dispersion of fixations was higher on diffuse compared with normal images, whereas for residents and radiologists, dispersion was highest on normal images. Despite this difference, students showed relatively high performance on normal images but low performance on focal and diffuse images. Viewing patterns were strongly influenced by bottom-up stimulus effects. Although viewing behavior of students was similar to that of radiologists, they lack knowledge that helps them diagnose the disease correctly. Copyright © 2012 John Wiley & Sons, Ltd. <s> BIB042 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Multiple-target visual searches are especially error prone; once one target is found, additional targets are likely to be missed. This phenomenon, often called satisfaction of search (which we refer to here as subsequent search misses; SSMs), is well known in radiology, despite no existing consensus about the underlying cause(s). Taking a cognitive laboratory approach, we propose that there are multiple causes of SSMs and present a taxonomy of SSMs based on searchers' eye movements during a multiple-target search task, including both previously identified and novel sources of SSMs. The types and distributions of SSMs revealed effects of working memory load, search strategy, and additional causal factors, suggesting that there is no single cause of SSMs. A multifaceted approach is likely needed to understand the psychological causes of SSMs and then to mitigate them in applied settings such as radiology and baggage screening. <s> BIB043 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> BACKGROUND ::: Digital breast tomosynthesis with 3D images might overcome some of the limitations of conventional 2D mammography for detection of breast cancer. We investigated the effect of integrated 2D and 3D mammography in population breast-cancer screening. ::: ::: ::: METHODS ::: Screening with Tomosynthesis OR standard Mammography (STORM) was a prospective comparative study. We recruited asymptomatic women aged 48 years or older who attended population-based breast-cancer screening through the Trento and Verona screening services (Italy) from August, 2011, to June, 2012. We did screen-reading in two sequential phases-2D only and integrated 2D and 3D mammography-yielding paired data for each screen. Standard double-reading by breast radiologists determined whether to recall the participant based on positive mammography at either screen read. Outcomes were measured from final assessment or excision histology. Primary outcome measures were the number of detected cancers, the number of detected cancers per 1000 screens, the number and proportion of false positive recalls, and incremental cancer detection attributable to integrated 2D and 3D mammography. We compared paired binary data with McNemar's test. ::: ::: ::: FINDINGS ::: 7292 women were screened (median age 58 years [IQR 54-63]). We detected 59 breast cancers (including 52 invasive cancers) in 57 women. Both 2D and integrated 2D and 3D screening detected 39 cancers. We detected 20 cancers with integrated 2D and 3D only versus none with 2D screening only (p<0.0001). Cancer detection rates were 5.3 cancers per 1000 screens (95% CI 3.8-7.3) for 2D only, and 8.1 cancers per 1000 screens (6.2-10.4) for integrated 2D and 3D screening. The incremental cancer detection rate attributable to integrated 2D and 3D mammography was 2.7 cancers per 1000 screens (1.7-4.2). 395 screens (5.5%; 95% CI 5.0-6.0) resulted in false positive recalls: 181 at both screen reads, and 141 with 2D only versus 73 with integrated 2D and 3D screening (p<0.0001). We estimated that conditional recall (positive integrated 2D and 3D mammography as a condition to recall) could have reduced false positive recalls by 17.2% (95% CI 13.6-21.3) without missing any of the cancers detected in the study population. ::: ::: ::: INTERPRETATION ::: Integrated 2D and 3D mammography improves breast-cancer detection and has the potential to reduce false positive recalls. Randomised controlled trials are needed to compare integrated 2D and 3D mammography with 2D mammography for breast cancer screening. ::: ::: ::: FUNDING ::: National Breast Cancer Foundation, Australia; National Health and Medical Research Council, Australia; Hologic, USA; Technologic, Italy. <s> BIB044 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> PURPOSE ::: To compare radiologists' diagnostic accuracy and recall rates for breast tomosynthesis combined with digital mammography versus digital mammography alone. ::: ::: ::: MATERIALS AND METHODS ::: Institutional review board approval was obtained at each accruing institution. Participating women gave written informed consent. Mediolateral oblique and craniocaudal digital mammographic and tomosynthesis images of both breasts were obtained from 1192 subjects. Two enriched reader studies were performed to compare digital mammography with tomosynthesis against digital mammography alone. Study 1 comprised 312 cases (48 cancer cases) with images read by 12 radiologists; study 2, 312 cases (51 cancer cases) with 15 radiologists. Study 1 readers recorded only that an abnormality requiring recall was present; study 2 readers had additional training and recorded both lesion type and location. Diagnostic accuracy was compared with receiver operating characteristic analysis. Recall rates of noncancer cases, sensitivity, specificity, and positive and negative predictive values determined by analyzing Breast Imaging Reporting and Data System scores were compared for the two methods. ::: ::: ::: RESULTS ::: Diagnostic accuracy for combined tomosynthesis and digital mammography was superior to that of digital mammography alone. Average difference in area under the curve in study 1 was 7.2% (95% confidence interval [CI]: 3.7%, 10.8%; P < .001) and in study 2 was 6.8% (95% CI: 4.1%, 9.5%; P < .001). All 27 radiologists increased diagnostic accuracy with addition of tomosynthesis. Recall rates for noncancer cases for all readers significantly decreased with addition of tomosynthesis (range, 6%-67%; P < .001 for 25 readers, P < .03 for all readers). Increased sensitivity was largest for invasive cancers: 15% and 22% in studies 1 and 2 versus 3% for in situ cancers in both studies. ::: ::: ::: CONCLUSION ::: Addition of tomosynthesis to digital mammography offers the dual benefit of significantly increased diagnostic accuracy and significantly reduced recall rates for noncancer cases. ::: ::: ::: SUPPLEMENTAL MATERIAL ::: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120674/-/DC1. <s> BIB045 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB046 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> To investigate interpretation of modern three-dimensional medical image displays, we have developed a method for analyzing visual gaze when the abnormality is both moving and changing in size. <s> BIB047 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> RATIONALE AND OBJECTIVES ::: To determine if the rate of major discrepancies between resident preliminary reports and faculty final reports increases during the final hours of consecutive 12-hour overnight call shifts. ::: ::: ::: MATERIALS AND METHODS ::: Institutional review board exemption status was obtained for this study. All overnight radiology reports interpreted by residents on-call between January 2010 and June 2010 were reviewed by board-certified faculty and categorized as major discrepancies if they contained a change in interpretation with the potential to impact patient management or outcome. Initial determination of a major discrepancy was at the discretion of individual faculty radiologists based on this general definition. Studies categorized as major discrepancies were secondarily reviewed by the residency program director (M.H.S.) to ensure consistent application of the major discrepancy designation. Multiple variables associated with each report were collected and analyzed, including the time of preliminary interpretation, time into shift study was interpreted, volume of studies interpreted during each shift, day of the week, patient location (inpatient or emergency department), block of shift (2-hour blocks for 12-hour shifts), imaging modality, patient age and gender, resident identification, and faculty identification. Univariate risk factor analysis was performed to determine the optimal data format of each variable (ie, continuous versus categorical). A multivariate logistic regression model was then constructed to account for confounding between variables and identify independent risk factors for major discrepancies. ::: ::: ::: RESULTS ::: We analyzed 8062 preliminary resident reports with 79 major discrepancies (1.0%). There was a statistically significant increase in major discrepancy rate during the final 2 hours of consecutive 12-hour call shifts. Multivariate analysis confirmed that interpretation during the last 2 hours of 12-hour call shifts (odds ratio (OR) 1.94, 95% confidence interval (CI) 1.18-3.21), cross-sectional imaging modality (OR 5.38, 95% CI 3.22-8.98), and inpatient location (OR 1.81, 95% CI 1.02-3.20) were independent risk factors for major discrepancy. ::: ::: ::: CONCLUSIONS ::: In a single academic medical center, major discrepancies in resident preliminary reports increased significantly during the final 2 hours of consecutive 12-hour overnight call shifts. This finding could be related to either fatigue or circadian desynchronization. Discrimination of these two potential etiologies requires additional investigation as major discrepancies in resident reports have the potential to negatively impact patient care/outcome. Cross-sectional imaging modalities including computed tomography and ultrasound (versus conventional radiography), as well as inpatient location (versus Emergency Department location), were also associated with significantly higher major discrepancy rates. <s> BIB048 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Expertise research has produced mixed results regarding the problem of transfer of expertise. Is expert performance context-bound or can the underlying processes be applied to more general situations? The present study tests whether expert performance and its underlying processes transfer to novel tasks within a domain. A mixed method study using eye-tracking and quantitative and qualitative analyses of think aloud protocols was conducted with medical professionals in radiology and nuclear medicine who diagnosed identical patient cases displayed with three different computer-based imaging technologies: a familiar, a semi-familiar, and an unfamiliar imaging technology. Results indicate that expert performance, as well as its underlying processes, transferred from the familiar to the semi-familiar, but not to the unfamiliar imaging technology. Educational implications of these findings are discussed in terms of their significance for designing technology-enhanced learning environments to promote the transfer of expertise. <s> BIB049 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Objectives ::: The objectives are To to compare the diagnostic performance of combined digital breast tomosynthesis (DBT) and digital mammography (DM) with that of DM alone, as a function of radiologists’ experience with DBT. <s> BIB050 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> RATIONALE AND OBJECTIVES ::: To determine the impact of mammographic breast density on the visual search process of radiologists when reading digital mammograms. ::: ::: ::: MATERIALS AND METHODS ::: Institutional review board approval was obtained. A set of 149 craniocaudal digital mammograms were read by seven radiologists, and observer search patterns were recorded. Total time examining each case, time to first hit the lesion, dwell time, and number of hits per area were calculated. The nonparametric Mann-Whitney U test was used for statistical evaluation. ::: ::: ::: RESULTS ::: In both low- and high-mammographic density cases, significant increases were observed in the time to first hit lesions when they were located outside, compared to overlying fibroglandular dense tissue (P = .001). Significantly longer dwell time (P = .003) and greater number of fixations (P = .0003) were observed when the lesions were situated within--rather than outside--the dense fibroglandular tissue. ::: ::: ::: CONCLUSIONS ::: Increased mammographic breast density changes radiologists' visual search patterns. Dense areas of the parenchyma attracted greater visual attention in both high- and low-mammographic density cases, resulting in faster detection of lesions overlying the fibroglandular dense tissue, along with longer dwell times and greater number of fixations, as compared to lesions located outside the dense fibroglandular regions. <s> BIB051 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Fundamental to the diagnosis of lung cancer in computed tomography (CT) scans is the detection and interpretation of lung nodules. As the capabilities of CT scanners have advanced, higher levels of spatial resolution reveal tinier lung abnormalities. Not all detected lung nodules should be reported; however, radiologists strive to detect all nodules that might have relevance to cancer diagnosis. Although medium to large lung nodules are detected consistently, interreader agreement and reader sensitivity for lung nodule detection diminish substantially as the nodule size falls below 8 to 10 mm. The difficulty in establishing an absolute reference standard presents a challenge to the reliability of studies performed to evaluate lung nodule detection. In the interest of improving detection performance, investigators are using eye tracking to analyze the effectiveness with which radiologists search CT scans relative to their ability to recognize nodules within their search path in order to determine whether strategies might exist to improve performance across readers. Beyond the viewing of transverse CT reconstructions, image processing techniques such as thin-slab maximum-intensity projections are used to substantially improve reader performance. Finally, the development of computer-aided detection has continued to evolve with the expectation that one day it will serve routinely as a tireless partner to the radiologist to enhance detection performance without significant prolongation of the interpretive process. This review provides an introduction to the current understanding of these varied issues as we enter the era of widespread lung cancer screening. <s> BIB052 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB053 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> While eye tracking research in conventional radiography has flourished over the past decades, the number of eye tracking studies that looked at multislice images lags behind. A possible reason for the lack of studies in this area might be that the eye tracking methodology used in the context of conventional radiography cannot be applied one-on-one to volumetric imaging material. Challenges associated with eye tracking in volumetric imaging are particularly associated with the selection of stimulus material, the detection of events in the eye tracking data, the calculation of meaningful eye tracking parameters, and the reporting of abnormalities. However, all of these challenges can be addressed in the design of the experiment. If this is done, eye tracking studies using volumetric imaging material offer almost unlimited opportunity for perception research and are highly relevant as the number of volumetric images that are acquired and interpreted is rising. <s> BIB054 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> When viewing a painting, artists perceive more information from the painting on the basis of their experience and knowledge than art novices do. This difference can be reflected in eye scan paths during viewing of paintings. Distributions of scan paths of artists are different from those of novices even when the paintings contain no figurative object (i.e. abstract paintings). There are two possible explanations for this difference of scan paths. One is that artists have high sensitivity to high-level features such as textures and composition of colors and therefore their fixations are more driven by such features compared with novices. The other is that fixations of artists are more attracted by salient features than those of novices and the fixations are driven by low-level features. To test these, we measured eye fixations of artists and novices during the free viewing of various abstract paintings and compared the distribution of their fixations for each painting with a topological attentional map that quantifies the conspicuity of low-level features in the painting (i.e. saliency map). We found that the fixation distribution of artists was more distinguishable from the saliency map than that of novices. This difference indicates that fixations of artists are less driven by low-level features than those of novices. Our result suggests that artists may extract visual information from paintings based on high-level features. This ability of artists may be associated with artists’ deep aesthetic appreciation of paintings. <s> BIB055 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> When people look for things in the environment, they use target templates—mental representations of the objects they are attempting to locate—to guide attention and to assess incoming visual input as potential targets. However, unlike laboratory participants, searchers in the real world rarely have perfect knowledge regarding the potential appearance of targets. In seven experiments, we examined how the precision of target templates affects the ability to conduct visual search. Specifically, we degraded template precision in two ways: 1) by contaminating searchers’ templates with inaccurate features, and 2) by introducing extraneous features to the template that were unhelpful. We recorded eye movements to allow inferences regarding the relative extents to which attentional guidance and decision-making are hindered by template imprecision. Our findings support a dual-function theory of the target template and highlight the importance of examining template precision in visual search. <s> BIB056 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Rationale and Objectives ::: In current practice, radiologists interpret digital images, including a substantial amount of volumetric images. We hypothesized that interpretation of a stack of a volumetric data set demands different skills than interpretation of two-dimensional (2D) cross-sectional images. This study aimed to investigate and compare knowledge and skills used for interpretation of volumetric versus 2D images. ::: Materials and Methods ::: Twenty radiology clerks were asked to think out loud while reading four or five volumetric computed tomography (CT) images in stack mode and four or five 2D CT images. Cases were presented in a digital testing program allowing stack viewing of volumetric data sets and changing views and window settings. Thoughts verbalized by the participants were registered and coded by a framework of knowledge and skills concerning three components: perception, analysis, and synthesis. The components were subdivided into 16 discrete knowledge and skill elements. A within-subject analysis was performed to compare cognitive processes during volumetric image readings versus 2D cross-sectional image readings. ::: Results ::: Most utterances contained knowledge and skills concerning perception (46%). A smaller part involved synthesis (31%) and analysis (23%). More utterances regarded perception in volumetric image interpretation than in 2D image interpretation (Median 48% vs 35%; z = −3.9; P < .001). Synthesis was less prominent in volumetric than in 2D image interpretation (Median 28% vs 42%; z = −3.9; P < .001). No differences were found in analysis utterances. ::: Conclusions ::: Cognitive processes in volumetric and 2D cross-sectional image interpretation differ substantially. Volumetric image interpretation draws predominantly on perceptual processes, whereas 2D image interpretation is mainly characterized by synthesis. The results encourage the use of volumetric images for teaching and testing perceptual skills. <s> BIB057 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> We examined the characteristics of endogenous exploratory behaviors in a generalized search task in which guidance signals (e.g., landmarks, semantics, visual saliency, layout) were limited or precluded. Individuals looked for the highest valued cell in an array and were scored on the quality of the best value they could find. Exploration was guided only by the cells that had been previously examined, and the value of this guidance was manipulated by adjusting spatial autocorrelation to produce relatively smooth and rough landscapes-that is, arrays in which nearby cells had unrelated values (low correlation = rough) or similar values (high correlation = smooth). For search in increasingly rough as compared with smooth arrays, we found reduced performance despite increased sampling and increased time spent searching after revelation of a searcher's best cell. Spatially, sampling strategies tended toward more excursive, branching, and space-filling patterns as correlation decreased. Using a novel generalized-recurrence analysis, we report that these patterns reflect an increase in systematic search paths, characterized by regularized sweeps with localized infilling. These tendencies were likewise enhanced for high-performance as compared with low-performance participants. The results suggest a trade-off between guidance (in smooth arrays) and systematicity (in rough arrays), and they provide insight into the particular strategic approaches adopted by searchers when exogenous guiding information is minimized. <s> BIB058 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Medical image interpretation is moving from using 2D- to volumetric images, thereby changing the cognitive and perceptual processes involved. This is expected to affect medical students' experienced cognitive load, while learning image interpretation skills. With two studies this explorative research investigated whether measures inherent to image interpretation, i.e. human-computer interaction and eye tracking, relate to cognitive load. Subsequently, it investigated effects of volumetric image interpretation on second-year medical students' cognitive load. Study 1 measured human-computer interactions of participants during two volumetric image interpretation tasks. Using structural equation modelling, the latent variable 'volumetric image information' was identified from the data, which significantly predicted self-reported mental effort as a measure of cognitive load. Study 2 measured participants' eye movements during multiple 2D and volumetric image interpretation tasks. Multilevel analysis showed that time to locate a relevant structure in an image was significantly related to pupil dilation, as a proxy for cognitive load. It is discussed how combining human-computer interaction and eye tracking allows for comprehensive measurement of cognitive load. Combining such measures in a single model would allow for disentangling unique sources of cognitive load, leading to recommendations for implementation of volumetric image interpretation in the medical education curriculum. Display Omitted Image interpretation in medicine moved from 2D- to volumetric images.Cognitive load of students interpreting medical images affected.Human computer interaction and time to locate relevant area predict cognitive load.Insights useful for avoiding cognitive overload in medical curriculum. <s> BIB059 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Background ::: No automated methods exist to objectively monitor and evaluate the diagnostic process while physicians review computerized medical images. The present study tested whether using eye tracking to monitor tonic and phasic pupil dynamics may prove valuable in tracking interpretive difficulty and predicting diagnostic accuracy. <s> BIB060 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB061 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> When searching through volumetric images [e.g., computed tomography (CT)], radiologists appear to use two different search strategies: “drilling” (restrict eye movements to a small region of the image while quickly scrolling through slices), or “scanning” (search over large areas at a given depth before moving on to the next slice). To computationally identify the type of image information that is used in these two strategies, 23 naive observers were instructed with either “drilling” or “scanning” when searching for target T’s in 20 volumes of faux lung CTs. We computed saliency maps using both classical two-dimensional (2-D) saliency, and a three-dimensional (3-D) dynamic saliency that captures the characteristics of scrolling through slices. Comparing observers’ gaze distributions with the saliency maps showed that search strategy alters the type of saliency that attracts fixations. Drillers’ fixations aligned better with dynamic saliency and scanners with 2-D saliency. The computed saliency was greater for detected targets than for missed targets. Similar results were observed in data from 19 radiologists who searched five stacks of clinical chest CTs for lung nodules. Dynamic saliency may be superior to the 2-D saliency for detecting targets embedded in volumetric images, and thus “drilling” may be more efficient than “scanning.” <s> BIB062 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB063 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB064 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> When searching for things in the world, we seldom encounter the static environment so often afforded by laboratory search tasks. Dynamic events tend to capture attention; however, Kunar and Watson ... <s> BIB065 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Background ::: Radiological techniques for breast cancer detection are undergoing a massive technological shift—moving from mammography, a process that takes a two-dimensional (2D) image of breast tissue, to tomosynthesis, a technique that creates a segmented-three-dimensional (3D) image. There are distinct benefits of tomosynthesis over mammography with radiologists having fewer false positives and more accurate detections; yet there is a significant and meaningful disadvantage with tomosynthesis in that it takes longer to evaluate each patient. This added time can dramatically impact workflow and have negative attentional and cognitive impacts on interpretation of medical images. To better understand the nature of segmented-3D visual search and the implications for radiology, the current study looked to establish a new testing platform that could reliably examine differences between 2D and segmented-3D search. <s> BIB066 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <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> BIB067 </s> What do we know about volumetric medical image interpretation?: a review of the basic science and medical image perception literatures <s> Introduction <s> Brain tumour detection and diagnosis requires clinicians to inspect and analyse brain magnetic resonance images. Eye-tracking is commonly used to examine observers’ gaze behaviour during such medical image interpretation tasks, but analysis of eye movement sequences is limited. We therefore used ScanMatch, a novel technique that compares saccadic eye movement sequences, to examine the effect of expertise and diagnosis on the similarity of scanning patterns. Diagnostic accuracy was also recorded. Thirty-five participants were classified as Novices, Medics and Experts based on their level of expertise. Participants completed two brain tumour detection tasks. The first was a whole-brain task, which consisted of 60 consecutively presented slices from one patient; the second was an independent-slice detection task, which consisted of 32 independent slices from five different patients. Experts displayed the highest accuracy and sensitivity followed by Medics and then Novices in the independent-slice task. Experts showed the highest level of scanning pattern similarity, with medics engaging in the least similar scanning patterns, for both the whole-brain and independent-slice task. In the independent-slice task, scanning patterns were the least similar for false negatives across all expertise levels and most similar for experts when they responded correctly. These results demonstrate the value of using ScanMatch in the medical image perception literature. Future research adopting this tool could, for example, identify cases that yield low scanning similarity and so provide insight into why diagnostic errors occur and ultimately help in training radiologists. <s> BIB068
Volumetric medical imaging, such as CT, magnetic resonance imaging (MRI), or digital breast tomosynthesis (DBT), helps retain the 3D nature of the body's internal structures by stacking multiple cross-sectional images. This imaging technique often results in a massive amount of information for the radiologist to evaluate BIB035 : a single chest radiograph is now often supplemented with a chest CT with a stack of 1000 high-resolution images (Fig. 1) . Unfortunately, abnormalities are sometimes very small relative to the overall size of the image. To illustrate this point, BIB052 calculated that lung cancer nodules between 4 mm and 10 mm in size make up 0.01% or less of the total volume in a typical chest CT scan. Lung cancer nodules of this size would only be visible on a handful of slices, rendering them undetectable for the vast majority of the radiologist's overall search time BIB052 . How do expert radiologists efficiently sort through all of this information and detect potential abnormalities? Are there optimal strategies for navigating through volumetric images? Unfortunately, despite decades of medical image perception research, relatively little is known about expertise in the interpretation of volumetric medical images. However, given the increasing number of volumetric images in radiology, answering these questions will likely be at the forefront of medical image perception research in the coming years BIB053 . The purpose of this manuscript is to review the literature and identify the current gaps in our understanding of volumetric image interpretation using a basic-science framework. First, we will discuss the merits of using basic scientific research on attention and memory to generate informed predictions about medical image perception. Next, we will discuss nine research areas that we feel best represent the current priorities of the field (Table 1 ). In each of these sections, we will discuss relevant findings from the basic science and medical image perception literatures and highlight promising areas for future research. This review should not be considered an exhaustive account of the literature. For example, the debate that surrounded the transition from analog to digital in radiology will not be covered in depth. Although the history of volumetric imaging is an interesting topic in its own right, it is beyond the scope of this review. In addition, we will not provide detailed discussion of the unique methodological challenges involved in volumetric imaging research and the approaches researchers have used to address them. Instead, we direct the reader to existing resources that cover this topic in depth  BIB054 . Rather, this manuscript is a selected review of the literature on volumetric image perception through the lens of basic research on visual attention and memory. Although many of these topics undoubtedly pertain to 2D imaging as well, the primary intent of this manuscript is to focus on issues most relevant to volumetric imaging and serve as a catalyst for future research in this area. What can we learn about medical image perception from basic scientific research? For several decades, researchers have sought to characterize how expert radiologists interpret medical images. Concurrently, cognitive scientists have been building a vast body of literature on visual search using tightly controlled laboratory tasks, such as "find the horizontal line amongst vertical lines." At first glance, these artificial tasks seem to have little in common with complex radiology tasks, such as identifying signs of breast cancer in a mammogram. However, at their core, both of these tasks can be characterized as visual search and rely on the same mechanisms  . In recent years, cognitive scientists have demonstrated the remarkable potential of applying findings from basic science to real-world tasks, such as radiology (Fig. 2 ). For example, observers in the laboratory often fail to notice a person walk through a basketball game wearing a gorilla suit when they perform a secondary task (e.g., counting the number of passes between players), a phenomenon known as "inattentional blindness" BIB014 . Similarly, 83% of radiologists missed a matchbook-sized gorilla image embedded into a slice of a chest CT scan when they were looking for signs of lung cancer . This research may help explain why incidental findings, which are unexpected abnormalities that are not the primary focus of search, are sometimes missed in radiology  . Examples of translational research from basic science to radiology, which have been thoroughly summarized elsewhere  , highlight the promise of using our knowledge of human cognition to make predictions about how radiologists search through medical images and when they will be most susceptible to error. However, volumetric imaging has created a new set of challenges for both radiologists and the perception scientists seeking to better understand them. Volumetric imaging was first introduced to clinical practice in the 1970s, but recent years have seen a dramatic increase in the size and number of volumetric images being interpreted in the radiology reading room BIB035 BIB053 . For example, the number of cross-sectional images at one institution increased tenfold between 1990 and 2010 BIB053 . Unfortunately, the majority of research on medical image perception is based on 2D images, such as chest radiographs. In basic science, there is an extensive literature on visual search in 2D laboratory tasks and a growing literature on search in the 3D world. However, volumetric images do not fall neatly into either of these categories (Fig. 2) . Nonetheless, there are a number of findings from these two bodies of literature that may provide insight on volumetric image interpretation, which we will highlight in this review. Although much of a radiologist's job can be characterized as decision-making, such as determining if a suspicious finding is cancerous or benign, this review will focus on how potential abnormalities are located and identified using visual search. To frame the discussion on visual search, we will primarily rely on the Guided Search model BIB005 . The Guided Search model posits that early information guides attention in a bottom-up or top-down manner toward specific features in the scene. Bottom-up guidance is driven by the properties of the stimulus itself. For example, in the absence of another task, a bright red poppy in a field of daisies is likely to capture attention. In contrast, top-down guidance is driven by the observer's internal state and selection history. Top-down attention can often override the effects of bottom-up mechanisms. For example, target representations held in memory can help guide attention away from salient distractors (e.g., the red poppy) and toward features in the environment that match the target's features. Together, bottom-up and top-down factors generate a priority map that directs attention to areas in the scene that are more likely to contain the target. What are the stimulus properties that guide attention in volumetric medical images? Bottom-up guidance in visual search can be highly effective when the most salient objects in the scene are consistent with your goals (e.g., identifying a large brain tumor), but harmful if your task involves detecting inconspicuous targets (e.g., small lung cancer nodules). Unfortunately, the most salient regions of medical images are not always the most informative for the radiologist. One well-established mechanism for limiting the influence of bottom-up information is through topdown knowledge about the task. All else being equal, experts should be able to better utilize a top-down strategy in medical image search than novices due to their extensive medical knowledge and past experience with similar images. For the same reason, the largest differences between experts and novices should be found in tasks that do not benefit from a bottom-up strategy. Broadly, these predictions have been well-supported in radiology, in addition to a number of other tasks and professions BIB028 BIB029 BIB055 BIB033 . For example, novices' eye-movements were closely predicted by a saliency map when analyzing single-slice brain CT scans for cerebrovascular incidents BIB036 , see also Nodine, Kundel, Lauver, & Toto, 1996 . Similarly, experts viewed clinically relevant areas of low salience longer than novices. However, if clinically relevant areas were high-salience, experts and novices' eye-movements did not differ BIB036 . Future research is needed to determine the features that influence the detectability of abnormalities in volumetric medical images. In chest radiographs, researchers have used eye-tracking to make distinctions between lesion properties that capture attention initially during search (as measured by time to first hit) and those that hold attention once the abnormality is detected (as measured by dwell time) BIB016 . In the context of guided search, "time to first hit" provides an index of the stimulus properties that more effectively guide attention to the lesion during visual search, whereas dwell time likely reflects recognition or decision-making processes. Although a number of characteristics (e.g., signal-to-noise ratio, conspicuity, location, and calcification) were evaluated, none of these features influenced how quickly attention would be directed to the relevant location in the image. However, both nodule size and conspicuity influenced dwell time on the lesion and predicted overall nodule detection rate. In contrast, BIB003 found that nodule conspicuity influenced both search and decision-making processes. Less conspicuous nodules were detected less often in a flash-viewing paradigm and were associated with more comparative scans to normal structures in the image during free viewing (defined as a fixation on the abnormality followed by a saccade and a refixation). In future work, it would be beneficial to evaluate the role of comparison scans for identifying different types of lesions in volumetric images. For example, the decision-making process for identifying a lung nodule might involve comparing how the abnormality's appearance changes through depth relative to normal structures in the image (e.g., blood vessels). In order to determine which stimulus features improve detectability in volumetric image search, it may be fruitful to lean on the basic science literature. According to , there are four guiding attributes that have been well-established by converging evidence in the literature: motion, color, orientation, and size. Although all of these features are undoubtedly important for detecting abnormalities in medical images, motion is an attribute that is uniquely applicable to volumetric images. In volumetric images, structures may appear to move along the 2D plane as the observer navigates through the depth of the image, which is thought to elicit smooth pursuit eye-movements as the observer tracks these structures through depth BIB054 . In addition, certain abnormalities, such as lung cancer nodules, appear to flicker in and out of view when scrolling through the depth of the image due to rapid changes in the structure's diameter. This phenomenon may mimic abrupt motion onset cues, which are known to capture visual attention BIB017 BIB012 BIB004 BIB015 . Furthermore, motion can serve as a filtering mechanism in visual search and strongly predicts where attention will be allocated in dynamic scenes BIB011 BIB008 BIB034 . In addition, even if movement is not a defining feature of the target, observers learn frequent associations between targets and their movements and use this information to guide search BIB065 . Although basic science suggests that motion cues serve as an effective form of guidance to a target, only a few studies have addressed this topic in medical image perception. For example, researchers found that artificially inducing motion cues into static images increased detection ability for both mammograms and chest radiographs BIB030 . In addition, researchers tested the prediction that searching in smaller windows would be superior to searching in larger windows in volumetric images because it would increase the ability to detect motion cues using foveal vision  . Although there were no overall differences in accuracy between conditions, a smaller image size was associated with locating abnormalities more quickly. Finally,  tested whether lung nodules are less likely to be detected early in the trial, when task-relevant motion onset cues (e.g., lung nodules) are likely obscured by simultaneous motion onset cues from task-irrelevant information (e.g., blood vessels). They found a significant effect of nodule location for novices, but not experts, which suggests that experts do not need to rely as heavily on these bottom-up signals for target detection. This is likely because experts have additional mechanisms, such as strong target representations and enhanced holistic processing, which also aid in the detection of abnormalities. What are common sources of error in volumetric medical image interpretation? During visual search, target representations in memory are thought to guide attention in a top-down manner toward features in the environment that match the target's features BIB037 BIB024 BIB022 . In typical laboratory paradigms, the observer searches for a single well-defined target that is either cued on each trial or remains the same throughout the experiment. However, searching for targets in more realistic circumstances where information about the target is degraded may be more challenging. Search performance is best when information about the target is precise (e.g., picture cues), and search is guided less effectively by imprecise (e.g., word cues) or categorical (e.g., cats versus Garfield) target cues BIB056 BIB019 . In addition, when multiple targets are present in an image (e.g., Garfield and Nermal), the second target is less likely to be detected after the first target is located BIB007 . This phenomenon was originally termed "satisfaction of search" which suggested the error was caused by prematurely terminating search following the detection of the first target BIB007 BIB001 . However, subsequent research has cast doubt on this explanation BIB009 , and these errors are thought to have multiple causes BIB043 . As a result, the term "subsequent search misses" has been proposed as a theory-neutral alternative . Unfortunately, a radiologist's task often represents the worst-case scenario for target representations: identifying an unspecified number of poorly defined abnormalities. Given these challenges, it is particularly important to consider how different imaging techniques might improve the radiologist's ability to locate abnormalities. For example, 2D medical imaging forces the observer to view organs as overlapping structures, which can obscure findings and provide inaccurate spatial relationships between anatomical structures. In contrast, although volumetric imaging is not truly 3D, there is less need to mentally translate anatomical structures from their 2D representations to the 3D world. Nonoverlapping structures, as well as the availability of motion cues, may improve the ability to detect abnormalities in volumetric images. Aside from breast cancer screening, direct comparisons between volumetric images and their two-dimensional counterparts are rare  BIB044 BIB031 BIB032 BIB040 BIB045 BIB038 . However, studies that used this approach have demonstrated that volumetric images are associated with improved accuracy BIB066 BIB063 BIB050 BIB025 BIB013 BIB010 . Critically, these accuracy differences are generally driven by both an increase in hit rate and a decrease in false alarms. However, volumetric imaging is also associated with a substantial cost: a large increase in search time and a decrease in overall coverage BIB066 BIB063 BIB067 . It is important to note that although volumetric imaging appears to be superior to other imaging techniques, both inter-observer variability and overall error rates in radiology suggest there is substantial room for improvement. In addition, recent research demonstrates that volumetric imaging may not be universally advantageous BIB067 . In a comparison between 3D breast tomosynthesis (DBT) and single-slice DBT, there were no differences in performance when readers were asked to identify masses. In contrast, 2D imaging was associated with better detection of microcalcifications. The researchers proposed that volumetric imaging leads to less image coverage and an increased reliance on parafoveal processing. Therefore, there is likely to be a cost of volumetric imaging when abnormalities cannot be readily detected in the periphery. In order to better understand the sources of error in volumetric image interpretation, it is beneficial to move beyond behavioral data. For example, if an observer misses a lesion, it is often unclear whether they failed to find it or located it but decided it should not be reported. For this reason, eyetracking has widely been used to determine why abnormalities are missed in various radiology tasks, such as lung cancer screening BIB020 . In general, both false positive and false negative decisions are associated with longer dwell time, which indicates that incorrect decisions are often associated with additional scrutiny BIB006 Manning, BarkerMill, Donovan, & Crawford, 2006) . Eye-tracking has also been used to identify three distinct types of errors: search errors occur when a lesion is never foveated, recognition errors occur when a lesion is fixated on briefly (for < 1 s) but not reported, and a decision error occurs when a lesion is fixated on for a prolonged period of time (> 1 s) but not reported (Fig. 3a , BIB002 . In lung cancer screening with chest radiographs, decision-making errors are the most common error type, followed by recognition and search errors BIB046 BIB002 . However, observed a relatively small proportion of decision errors in lung cancer screening using chest CT scans. In fly-by 3D colonography, a virtual navigation through an endoluminal reconstruction of the colon, the majority of errors were identified as recognition errors and search errors were almost non-existent BIB047 . In addition, errors were evenly distributed between search and recognition errors in the identification of microcalcifications in DBT BIB067 . However, the errors were primarily recognition errors for the identification of masses. These studies are good examples of extending current eye-tracking metrics to volumetric images, which allows direct comparisons between these modalities. By doing so, researchers have discovered that volumetric imaging may improve the ability to accurately identify an abnormality once it has been located across a variety of tasks, which may be a benefit of non-overlapping structures BIB067 BIB047 . However, the distribution of errors can differ substantially based on the nature of the task or even between search strategies within same task BIB067 . In future research, it will also be important to identify how the distribution of errors changes over the course of training in the interpretation of volumetric medical images, which may ultimately provide insight on the type of assistance (e.g., computer-aided detection) that would be most beneficial across levels of experience. Although similar approaches have been used to classify errors in 2D and volumetric images ; BIB067 BIB047 , it is largely unclear whether the thresholds for these categories are appropriate for volumetric images. It is also important for researchers to consider the appropriateness of applying these categories to different types of tasks. Certainly, an abnormality that is not fixated on indicates some level of search error, but determining whether fixational dwell time for an intermediate time (e.g., 500 ms) constitutes a recognition or decision error likely depends on both the task at hand and the level of expertise of the observer. For example, overall nodule dwell time in chest radiographs was lower for experts than trainees, which was mirrored by a shift to more recognition errors relative to decision-making errors BIB046 ). An alternative approach to Kundel's classic error categorization was recently advanced by . After recording eye movements for thousands of trials, they used a data-driven approach for the task in question (a multiple-target, visual search task in their case) to describe different types of errors. Data-driven approaches allow the threshold between recognition and decision errors to be adjusted for a given stimulus based on the distribution of dwell times or the average search slope. Using this approach, identified a threshold~25% of the value typically used as a threshold in medical image perception. Notably, there was little evidence to support a clear, qualitative distinction between recognition and decision errors. Rather, the data could be more adequately described by models of perceptual decision-making, such as drift diffusion BIB027 , that posit that evidence is slowly accumulated during the fixation on an item until a decision threshold is reached. From this perspective, recognition and decision errors occur on a continuum rather than as distinct categories. In addition, demonstrated that search errors for the second target could be further sub-divided into novel categories. On some trials, the search was terminated as soon as the first target was identified with no attempt to locate the second target ("strategy" error). On other trials, the first target was re-fixated on during search ("resource depletion" error), which suggests working memory resources might have been depleted by maintaining information about the first target . This research highlights that there is not a one-size-fits-all approach to error classification between tasks, as well as the potential for data-driven classification to provide additional insight on sources of error in visual search. Although this approach requires a large amount of data, which can be difficult to collect with radiology observers, it may be informative to use a data-driven method to create a taxonomy of errors in volumetric image search. For example, an abnormality might be missed in a volumetric image if the abnormality is visible during search but never fixated on, but a miss error could also occur if the slice of the image that contains the abnormality is never visited. Although these would both be considered search errors under Kundel's classification system, these likely represent different sources of error. What are the consequences of increased cognitive load and how can they be overcome? In light of the increased ability to detect abnormalities in volumetric images, one might expect volumetric images to be associated with a reduced cognitive load. However, medical students report greater mental effort when viewing volumetric images, which may be due to the increased size, complexity, and evaluation time associated with these images BIB059 . This finding appears to be supported by pupil size, a physiological measure of cognitive load BIB026  , which increases with search time in volumetric images BIB059 . Along similar lines, recent work with breast pathologists examining digital pathology slides has found that pupil diameter is sensitive to perceived case difficulty: more difficult cases were generally associated with a larger pupil diameter BIB060 . Findings from a wide variety of sources suggest that visual search is impaired when working memory is taxed. Concurrent spatial working memory load reduces the efficiency of visual search in both laboratory and applied tasks, such as driving BIB021 BIB018 . In addition, salient bottom-up features are known to capture attention more effectively under cognitive load BIB039 . Typically, observers in natural tasks seek to minimize their cognitive load by frequently scanning their environment, particularly when memory load is high and the task is unpredictable (Droll & Hayhoe, 2007) . This effect seems to be exaggerated in novices: weaker chess players favor moves that will reduce working memory load, such as decreasing the number of pieces on the board  . In radiology, increases in cognitive load and fatigue may have a detrimental impact on patient care. Discrepancies increase during the final hours of a long work day, and volumetric images have been identified as a risk-factor for these discrepancies BIB048 . After viewing CT images, observers have reduced accuracy, greater visual fatigue, and increased visual strain BIB041 . Similarly, think-aloud protocols reveal that radiologists verbalize more often about efficient search strategies and image manipulation skills in volumetric images than in 2D images BIB057 . Furthermore, one study suggests that residents are more affected by fatigue than experts while detecting abnormalities in abdominal CT BIB061 . In future research, it will be necessary to determine which search strategies best offset the cognitive load associated with volumetric medical images. What are the best strategies for searching through depth across different tasks and modalities? One particularly promising avenue of research is to explore how variation in scrolling behavior might relate to search performance. found that adopting a strategy of rapidly "drilling" through depth while maintaining fixation was superior to "scanning" the x and y plane while slowly moving through depth during lung cancer screening (Fig. 4) . Although this study did not test the use of motion cues directly, it is possible that drilling allows the observer to more effectively take advantage of transient motion cues to distinguish blood vessels from nodules that appear to "pop in and out of view" while scrolling through depth. In support of this proposal, BIB062 found that scanners and drillers make use of different bottom-up cues in lung cancer screening tasks. It appears that drillers are better able to make use of salient motion cues, whereas scanners' search behavior is driven largely by 2D saliency. In addition to overall performance differences, the distribution of errors differed between scanners and drillers: drillers tended to have more recognition errors than scanners, and scanners tended to make more search errors than drillers. At present, it is unclear how these search strategies emerge over the course of training. found that drillers tended to read more CT cases per week than scanners. However, there were no differences in search strategy based on years of experience, and the sample size was not large enough to fully tease apart the effects of search strategy versus experience in relation to overall performance. In future research, it will be beneficial to investigate the best search strategies in volumetric images across different tasks and modalities. Search strategies that are most effective for a given task (e.g., detecting focal abnormalities, such as lung cancer nodules) may not be optimal for abnormalities defined by different bottom-up properties (e.g., detecting diffuse abnormalities, such as pneumonia). There are some good examples of these comparisons from studies using 2D medical images (e.g., BIB049 BIB023 BIB016 BIB051 . For example, when viewing chest radiographs, different search patterns are elicited for diffuse abnormalities, focal abnormalities, and normal images BIB042 . Furthermore, experts and novices have different patterns of behavior based on the type of abnormality. Diffuse abnormalities generally led to shorter and more dispersed fixations, but this effect was more pronounced in the students. In contrast, focal abnormalities were characterized by longer fixations at a given location. Notably, in a direct comparison between breast tomosynthesis and chest CT, BIB063 found that breast tomosynthesis led to a more rigorous drilling strategy than chest CT. Furthermore, no observers adopted a scanning strategy. Similarly, although both scanners and drillers could be identified in examinations of abdominal and pelvic CT, there was no accuracy advantage associated with being a driller (Kelahan et al., 20192019) . The scanner/driller distinction has also recently been extended to the realm of digital pathology, where clinicians pan and zoom into large images to more closely view suspicious regions BIB064 . In this domain, scanning appears to be the dominant strategy, but there were no differences in performance. In future research, it may be beneficial to evaluate the stimulus properties that influence the relative proportion of these strategies in volumetric images in a more systematic manner. A recent study approached the question of interobserver variability in scan patterns using a novel tool called ScanMatch BIB068 . The ScanMatch method compares fixation sequences across observers by assigning a letter value to each region and generating a string sequence for each participant. These strings are then compared between observers and a similarity score is obtained. In this study, observers viewed two runs of a fixed speed presentation of brain MRI scans. Overall, experts engaged in more similar scan patterns than novices. In addition, greater similarity was associated with better performance. These results could be explained in a number of ways. First, it is possible that experts are driven by statistical irregularities picked up in the first presentation of the stimulus, which is supported by increased similarity scores for true positives and lower similarity scores for false negatives. However, the same pattern was not found for true negatives, which led the authors to suggest that experts might instead use more systematic search strategies in the absence of statistical irregularities. Consistent with this view, observers adopt endogenous systematic search strategies in visual displays that are lacking in features that typically guide search behavior, such as saliency and semantic information BIB058 . In addition, systematic search strategies were more closely associated with the strongest performers. In future research, it would be interesting to test these predictions more directly in volumetric image search, particularly as it relates to the reliability of scrolling behavior through depth using more clinically-valid free-scroll paradigms.