Until now, no specific therapies are available to inhibit pancreatic fibrosis, a constant pathological feature of chronic pancreatitis and pancreatic cancer. One major reason is the incomplete knowledge of the molecular principles underlying fibrogenesis in the pancreas. In the past few years, evidence has been accumulated that activated pancreatic stellate cells (PSCs) are the predominant source of extracellular matrix (ECM) proteins in the diseased organ. PSCs are vitamin A-storing, fibroblast-like cells with close morphological and biochemical similarities to hepatic stellate cells . In response to profibrogenic mediators such as various cytokines, PSCs undergo an activation process that involves proliferation, exhibition of a myofibroblastic phenotype and enhanced production of ECM proteins. The intracellular mediators of activation signals, and their antagonists, are only partially known so far. Recent data suggest an important role of enzymes of the mitogen-activated protein kinase family in PSC activation. On the other hand, ligands of the nuclear receptor PPARγ (peroxisome proliferator-activated receptor γ) stimulate maintenance of a quiescent PSC phenotype. In the future, targeting regulators of the PSC activation process might become a promising approach for the treatment of pancreatic fibrosis. Excessive production of connective tissue molecules forming the extracellular matrix (ECM) is a pathological process relevant to diseases of many organ systems, including liver, lung, kidney, bowel and pancreas. The resulting fibrosis frequently leads to a progressive loss of specific organ functions. In the past two decades, fibrogenesis has been intensively studied by a large number of laboratories, and a great deal of scientific information has been accumulated regarding the pathogenesis of fibrosis in various organs. Until a few years ago, pancreatic fibrosis, however, remained an exception: although known for a long time as a central pathological feature of both chronic pancreatitis and pancreatic cancer ,2, its cBoth chronic pancreatitis and pancreatic cancer are accompanied by an organ fibrosis ,2. The pin vitro data gave rise to the hypothesis that PSCs might play a pivotal role in pancreatic fibrogenesis.Fibroblast activation has been reported to be a common event in pancreatitis already more than a decade ago -9, but tin vivo studies using experimental models of pancreatic fibrosis: Infusion of trinitrobenzene sulfonic acid (TNBS) into the pancreatic duct of rats causes a pancreatic necroinflammation followed by fibrosis [In the meantime, this hypothesis has been supported by the results of several fibrosis . In TNBSfibrosis . Importafibrosis . Anotherfibrosis . Time cofibrosis . In micefibrosis ,16. In afibrosis .Recently, it has also been suggested that PSCs contribute to regeneration early after acute necrotising pancreatitis in humans .in vitro and in vivo data suggest that PSCs are essentially involved in the development of pancreatic fibrosis.Together, Based on the results of various recent studies, extracellular factors involved in PSC activation may be divided into two major groups: (I) cytokines/growth factors ,19-22 anCytokines stimulating PSC activation include platelet-derived growth factor (PDGF) ,19,21,22In vitro, angiotensin II (ATII) stimulates PSC proliferation [Recent studies have also implicated the pancreatic renin-angiotensin system ,33 in paferation ,38 and ihepatic stellate cells from lipid peroxidation by enhancing biological activities against oxidative stress, resulting in an inhibition of activation [Cytokines that act as antagonists of PSC activation have not been systematically studied so far. Recently, it has been shown that IFN-α protects tivation . Furthertivation , IFN-β ativation  on HSCs tivation . The effin vitro data suggest that ethanol directly acts on PSCs and induces activation [Although it is known for a long time that chronic pancreatitis, associated with fibrosis, is a serious complication of alcohol abuse, the pathogenesis of alcoholic pancreatitis still remains to be fully elucidated [reviewed in ]. In rectivation : Culturetivation . Althougsystematic elucidation of signaling pathways in PSCs will also be one of the most important issues for future research. So far, research regarding intracellular signaling in PSCs has focused on two main aspects: the role of enzymes of the mitogen-activated protein kinase (MAPK) family and the transcriptional control of PSC activation.In the past two years, analysis of signal transduction pathways regulating PSC function has become a focus of attention. As detailed below, identification of signaling molecules that play a crucial role in PSC activation is a promising approach for the development of therapeutic strategies to inhibit pancreatic fibrosis. It is therefore envisaged that the MAPKs are a family of serine/threonine specific protein kinases with a wide range of biological functions in the regulation of fundamental cellular processes, including gene expression, proliferation and cell survival/apoptotic cell death -46. In mThe other two major MAP kinase pathways, involving JNK and p38, are well-established mediators of signals induced by pro-inflammatory cytokines and cellular stressors (e.g., oxidant stress, UV irradiation) . In PSCsin vitro by regulating the actin cytoskeleton [Two other intracellular signal transduction pathways that have recently been studied regarding their role in PSC activation are the phosphatidylinositol 3 (PI 3)-kinase and the Rho-Rho kinase (ROCK) pathway. The results suggest that PI 3-kinase activity is required for PDGF-stimulated PSC migration but not proliferation ,55. The skeleton .Cytokine and growth factor receptors exert their effects on the expression of target genes through signaling cascades that regulate the activity of a characteristic set of transcription factors. Recently, the group of the author has analyzed the activation profiles of activator protein (AP)-1 ,58, signIn the transduction of TGF-β receptor-derived signals into the nucleus, Smad transcription factors play a central role ,64. Stud2 and troglitazone (an antidiabetic drug of the thiazolidinedione group) act as antagonists of PSC activation in vitro that decrease cell proliferation and expression of α-SMA [Recent studies have implicated the nuclear hormone receptor peroxisome proliferator-activated receptor γ (PPARγ) in the inhibition of stellate cell activation in liver -69 and pof α-SMA . In Wistof α-SMA . The antof α-SMA . Thus, tWhile the role of activated PSCs in pancreatic fibrosis is well established, the physiological functions of their quiescent precursors are less well understood. Importantly, PSCs are not only a source of ECM but also of matrix-degrading enzymes of the MMP  family and their inhibitors . Thus, PSCs have been shown to secrete MMP-2, MMP-9 and MMP-13 and to express TIMP-1 and TIMP-2 . It appeThe embryonic origin of PSCs still remains to be determined. Very recently, Seaberg et al.  reportedUntil now, the physiological consequences of vitamin A-storage in PSCs remain unclear. It has recently been shown by the group of the author that the vitamin A derivate all-trans retinoic acid has complex effects on PSC function and acts, at least in part, as an antagonist of the activation process . It is, In the past, research regarding PSC biology has almost exclusively focused on the molecular basics of the activation process. However, given that participation in regeneration after pancreatic injury is an important function of activated PSCs, it is apparent that a disturbance of the inactivation or elimination of activated PSCs, rather than PSC activation itself, is the pathological process that leads to fibrosis. So far, it has not been systematically studied whether activated PSCs are capable of returning into a quiescent stage after fulfilling a repair function. Alternatively, elimination by apoptosis might be important in terminating the wound-healing response after pancreatic injury .Finally, work on the complex relationships between PSCs and pancreatic tumor cells is still in its infancy. Very likely, activation of PSCs not simply accompanies tumor progression but plays an active role in this process. Thus, it has been recently been shown that pancreatic cancer growth and progression is accelerated through complex functional interactions between carcinoma cells and PSCs . FurtherStudies on PSC biology are still hampered by the limited availibility of primary cells. Possibly, recently established pancreatic stellate cell lines ,82 will hepatic stellate cell activation, such as interferons.Given that activated PSCs are the principle effector cells in pancreatic fibrosis, targeting PSCs might become a promising therapeutic approach. Principle strategies that can be envisaged include an interruption/reversion of the activation process as well as an elimination of activated PSCs, e.g. through an induction of apoptosis. So far, potential antifibrotic drugs have been mainly tested in models of liver fibrosis (reviewed in ). The exAs described above, studies on the regulation of PSC activation at the intracellular level have identified key mediators of stimulatory and inhibitory signals. Targeting molecules such as PPARγ, MAP kinases, PI 3-kinase, or Smad proteins might become an important approach for the treatment of pancreatic fibrosis in the future. Further progress in the development of antifibrotic therapies can be expected from the ongoing elucidation of the molecular principles of PSC activation.PSCs play a crucial role in pancreatic fibrogenesis Figure . Ethanol


The 12-item General Health Questionnaire (GHQ-12) is widely used as a unidimensional instrument, but factor analyses tended to suggest that it contains two or three factors. Not much is known about the usefulness of the GHQ-12 factors, if they exist, in revealing between-patient differences in clinical states and health-related quality of life.We addressed this issue in a cross-sectional survey of out-patients with psychological disorders in Singapore. The participants (n = 120) completed the GHQ-12, the Beck Anxiety Inventory, and the Short-Form 36 Health Survey. Confirmatory factor analysis was used to compare six previously proposed factor structures for the GHQ-12. Factor scores of the best-fitting model, as well as the overall GHQ-12 score, were assessed in relation to clinical and health-related quality of life variables.The 3-factor model proposed by Graetz fitted the data better than a unidimensional model, two 2-factor models, and two other 3-factor models. However, the three factors were strongly correlated. Their values varied in a similar fashion in relation to clinical and health-related quality of life variables.The 12-item General Health Questionnaire contains three factors, namely Anxiety and Depression, Social Dysfunction, and Loss of Confidence. Nevertheless, using them separately does not offer many practical advantages in differentiating clinical groups or identifying association with clinical or health-related quality of life variables. Recent studies of disease burden have demonstrated the importance of psychological disorders. For instance, depression was the fourth leading cause of disease burden, accounting for 4.4% of total disability adjusted life years in the world in 2000 . The 12-While the longer versions of the GHQ are normally considered multidimensional, the GHQ-12 is often regarded as measuring only a single dimension of psychological health. For example, Corti  analyzedUsing confirmatory factor analysis (CFA) to analyze the BHPS data, Cheung  comparedWhile the structure of the GHQ-12 has been studied using factor analysis methods, the construct validity and usefulness of those resulting factors are not often tested. The question is whether the additional information provided by the 2 or 3 factors, if they exist, is clinically useful. In other words, will multiple scores be more useful than a total single score in helping us to understand respondents' health status?The purpose of this study was therefore two-fold. First, we aimed to compare the previously proposed models of the GHQ-12 in an oriental population and identify the best-fitting one. It was not our objective to assess their absolute level of fit or to derive new model or version of the GHQ. Second, we aimed to assess whether the factors identified relate to clinical and health-related quality of life variables in different ways.A consecutive sample of outpatients with anxiety disorders and/or depressive disorders was recruited from a psychiatric clinic at a tertiary hospital in Singapore. Inclusion criteria were the presence of any anxiety disorder and/or major depressive disorder, literacy in English or Chinese, and completion of an informed consent form. Patients with organic brain syndrome or psychosis were excluded.During routine consultation visits, diagnoses of recruited patients were ascertained by a psychiatrist using DSM-IV criteria and the severity of their psychiatric disorders was assessed using a Clinical Global Impression (CGI) scale, which ranges from 1 (very mild) to 5 (very severe). Patients were then given a questionnaire containing the General Health Questionnaire (GHQ-12) , the BecThe General Health Questionnaire (GHQ-12) consists of 12 items, each assessing the severity of a mental problem over the past few weeks using a 4-point scale (from 0 to 3). The score was used to generate a total score ranging from 0 to 36, with higher scores indicating worse conditions . The ChiThe Beck Anxiety Inventory (BAI) is a valid and reliable self-report checklist for anxiety symptoms . This inThe Short Form 36 Health Survey (SF-36)  is a 36-Various factor structures of the GHQ-12 were tested by confirmatory factor analysis. Model I was unidimensional. Model IIA contained 2 factors: General Dysphoria and Social Dysfunction . Model IMethodologists have emphasized that it is desirable to use different indicators to examine a model's goodness-of-fit . The fitThe best-fitting model was examined in detail. The Kruskal-Wallis test was used to compare the GHQ-12 overall and factor scores of patients with different diagnosis. Pearson's correlation coefficient (r) was used to assess the association between GHQ-12 scores and various variables, namely Beck Anxiety Inventory, Clinical Global Impression and SF-36 scores. The Fisher's Z transformation was used to produce 95% confidence interval.A total of 120 participants (63 man and 57 women) were included in the analysis (Table Table Figure Having established that Graetz's 3-factor model fitted the data better than the other models, we calculated the factor scores as unweighted sums of the items concerned. From figure Table Several previous confirmatory factor analyses found that the 3-factor model of Graetz gave better fit to survey data from Australia , BritainThe one-dimensional model was the worst according to all three goodness-of-fit indices.The three factors in the model proposed by Graetz were found to be strongly correlated with each other, with correlation coefficients in the neighborhood of 0.8 to 0.9. Such strong correlations suggest that even if there were indeed three different factors, in practice it is quite difficult to differentiate them. The study of French and Tait  also shoTwo limitations of the study should be noted. Firstly, the sample size was somewhat small for confirmatory factor analysis. Secondly, the participants were clinical cases. This homogeneity might have made it more difficult to detect variations in GHQ-12 scores. We believe that the question about the relative plausibility of various factor models have been sufficiently answered by this and several previous studies -12. NeveSeveral studies, including the present one, have found that Graetz's 3-factor model of the GHQ-12 is more plausible than other models. However, the factors were strongly correlated and difficult to discern. Our analysis of the three GHQ scores in relation to clinical variables and aspects of health-related quality of life did not appear to be more informative than analysis of a single overall GHQ-12 score. As such, from a pragmatic point of view we consider it acceptable to use this instrument as a one-dimensional measure. Unless one has specific questions that are best answered by a subset of the three factors, there is no need to consider the multi-dimensionality.FG carried out the confirmatory factor analysis, interpreted the findings, and drafted part of the manuscript. NL designed the study, participated in the development of the statistical framework and interpreted the findings. JT participated in the study design, discussion of the statistical framework, and the interpretation of findings. CF participated in the study design and carried out the data collection and clinical assessments. SCL participated in the study design and discussion and interpretation of findings. YBC conceived of the study, developed the statistical framework, carried out part of the statistical analysis, and drafted part of the manuscript. All authors read and approved the final manuscript.


Diagnosing chronic heart failure is difficult, especially in mild cases or early in the course of the disease, and guidelines are not easily implemented in everyday practice. The aim of this study was to investigate general practitioners' diagnostic reasoning about patients with suspected chronic heart failure in comparison with recommendations in European guidelines.Think-aloud technique was used. Fifteen general practitioners reasoned about six case vignettes, representing authentic patients with suspected chronic heart failure. Information about each case was added successively in five steps. The general practitioners said their thoughts aloud while reasoning about the probability of the patient having chronic heart failure, and tried to decide about the diagnosis. Arguments for and against chronic heart failure were analysed and compared to recommendations in guidelines.Information about ejection fraction was the most frequent diagnostic argument, followed by information about cardiac enlargement or pulmonary congestion on chest X-ray. However, in a third of the judgement situations, no information about echocardiography was utilized in the general practitioners' diagnostic reasoning. Only three of the 15 doctors used information about a normal electrocardiography as an argument against chronic heart failure. Information about other cardio-vascular diseases was frequently used as a diagnostic argument.The clinical information was not utilized to the extent recommended in guidelines. Some implications of our study are that 1) general practitioners need more information about how to utilize echocardiography when diagnosing chronic heart failure, 2) guidelines ought to give more importance to information about other cardio-vascular diseases in the diagnostic reasoning, and 3) guidelines ought to treat the topic of diastolic heart failure in a clearer way. Chronic heart failure (CHF) is a major cause of morbidity and mortality and it has a considerable impact on the health care system . In a reThe European Society of Cardiology adopted guidelines for diagnosing CHF in 1995, and these were revised in 2001 -9. Swedia) one or more typical symptoms (at rest or during exercise), b) objective evidence of cardiac dysfunction (at rest), and c) response to treatment directed towards CHF (in cases where diagnosis is in doubt). Criteria a and b should be fulfilled in all cases. Echocardiography (ECHO) is mentioned as the single most effective tool in widespread clinical use for objective assessment of cardiac dysfunction. In the algorithm for the diagnosis of CHF, a sequence of investigations is recommended: suspect CHF because of symptoms and signs; assess presence of cardiac disease by electrocardiography, X-ray or Natriuretic peptides (where available); imaging by echocardiography; assess aetiology, degree, precipitating factors and type of cardiac dysfunction; additional diagnostic tests where appropriate; choose therapy. Table The full versions of the above-mentioned guidelines are comprehensive documents, covering epidemiology, aetiology, pathophysiology and diagnostic methods, but may be difficult to apply to specific diagnostic situations . HoweverRelatively few studies on how patients suspected of having CHF are diagnosed have been performed in primary health care settings, and most of them report over-diagnosis ,4,14-16.Process-tracing techniques are used to study the cognitive processes involved in decision-making such as, for example, how judgements change over time as new information is presented, and which decision rules are used . A methoThe value of conclusions reached in such studies depends on the validity of the think-aloud method, and on the reliability of the coding process. Thinking aloud while performing a task often lengthens the time for completing the task, but does not seem to change the accuracy of task fulfilment or the cognitive processes . In a ren = 61) were listed and contacted in a random order. The distance from central Stockholm was chosen for practical reasons. In each health care centre the GPs were contacted in a random order by one of the authors (YS). Only one GP at each centre was included in the study, and this person had to be a specialist in family medicine. We contacted the GPs during their regular telephone hour, during the period October 2001 to October 2002. Our goal was to include 15 GPs in the study.All health care centres in northern Stockholm within a distance of 20–30 km from the city centre  years, they were on average 52.7 (range 42–62) years of age, and six of them were men. The non-participating GPs were on average 52.7 (range 35–62) years of age, and seven of them were men.Six case vignettes (CV), based on authentic patients, were presented to the participants. The information presented in the case vignettes was obtained from the patient records and included information about relevant diseases (e.g. coronary heart disease, stroke, diabetes), lifestyle factors , symptoms, signs, electrocardiography (ECG), chest X-ray findings, and ECHO. Chest X-ray and ECHO results were presented in the same format as in the patient records. ECHO results could contain information about ejection fraction (EF), valvular disorders and ventricular wall motility. The diagnoses made by the attending cardiologists  were used as a reference standard when assessing the participants' diagnostic accomplishments.The six cases were selected to represent patients with various types of potential diagnostic problems: A "prototypical" CHF patient (CV2), a patient with both CHF and chronic obstructive pulmonary disease (COPD) (CV6), a patient with CHF, tachycardia and mitral valve insufficiency (CV3), an obese non-CHF patient with normal ECG and EF (CV5), a non-CHF patient with COPD (CV4) and a non-CHF patient with alcohol abuse and a metabolic syndrome (CV1). For one of the cases (CV3) there was a disagreement between the diagnosis according to the cardiologists and the diagnosis that could be deduced from a simplistic interpretation of the guidelines. This patient had typical clinical findings including gallop rhythm, cardiomegaly, and pulmonary congestion, but normal left ventricular function according to ECHO. It could therefore be categorized as not CHF according to the definition given in the guidelines. However, this patient also had a mitral valve insufficiency, which can give a "false normal" ejection fraction value: the left ventricle is emptied both forward (cardiac output) and backward .Before the sessions the GPs had received written information about the aim of the study  and about the method , but not about the kind of medical problems that would be presented to them. The study was conducted at the GPs' offices. All visits and recordings were made by one of the authors (YS). The participants were instructed that six authentic patients, suspected by GPs to have CHF, would be presented, and that their task was to say aloud their thoughts about the case, and to try to decide whether the patient had CHF or not.The order of the cases was the same for all participants. The order in which the information was presented was arranged to be as realistic as possible in relation to clinical practice (first history and symptoms, then findings, and then results of investigations). Each vignette was presented on a computer screen in five successive steps using QA software . All preThe doctors first got a test case (not recorded) in order to get acquainted with the think-aloud method, and then continued with the six study cases. The only intervention from the researcher during the think-aloud session was that a participant who was silent for more than about 15 seconds was reminded to say his or her thoughts aloud about the information presented . All sesAll information in the case vignettes that was of relevance for the diagnosis and that could take on different values was considered to be variables. Fifty variables were defined: 19 of them were included in all six vignettes (e.g. symptoms, signs and investigations mentioned in the guidelines), six in five, one in four, six in three, one in two, and 17 in one vignette . For each case vignette, the presented variables were coded for content and value Table .2) as an argument against CHF. For each participant, a specific evaluation of each variable value was only counted once for each case vignette in order not to give more weight to thoughtful repetitions of an argument than to a single, firm statement. However, if a participant used the same variable value as an argument both for and against the diagnosis of CHF, both evaluations were coded. Ten percent of the 90 case vignette protocols were selected at random and coded independently by two of the authors (YS, LB) to estimate the interrater agreement of the coding process. The rest of the protocols were coded by one of the authors (YS).For each participant, every mention of a variable was coded for how the GP seemed to use it: as an argument for the diagnosis of CHF, as an argument against CHF, or as not being of any explicit use for the diagnosis (mentioned only). "He has basal rales. This guy has CHF!" is an example of a participant using the variable "rales"  as an argument for CHF. "So I'm not really sure that he has got CHF. Just a moderate cardiac enlargement, no, I wouldn't think so" is an example of a participant using the variable "relative heart volume"  in three categories: CHF or probably CHF; uncertainty about diagnosis; probably not CHF or not CHF.The participants were not forced to express their diagnostic judgements in a specific format, and their free verbal statements therefore had to be interpreted and coded. Two of the authors (YS, LB) independently classified all the diagnostic judgements (Stata 8.0 was used for the statistics. Cohen's kappa test (κ) was used to determine interrater agreement regarding the coding of the think-aloud protocols and the classification of the diagnostic judgements. Kappa values are classified as follows: <0, worse than chance; 0 to 0.2, poor; 0.21 to 0.4, fair; 0.41 to 0.6, moderate; 0.61 to 0.8, good; and >0.8, very good .The research ethics committee of Huddinge University Hospital approved the study.The randomly selected test protocols contained 322 segments of propositions, 36 of which were excluded since they contained variables that were not going to be investigated in this study (e.g. treatment suggestions). There was disagreement between the two coders about the content of variables in 14 of the remaining 286 segments (4.8%). The remaining 272 segments were then tested for interrater agreement on argument values , which was 95% (κ 0.85).The interrater agreement was 92% (κ 0.85). For the few diagnostic judgements where there was initial disagreement, it was possible to agree upon an interpretation.The information that was used most frequently in diagnostic arguments was the ejection fraction value on ECHO, pulmonary congestion, and cardiac volume Figure . The mosSymptoms and signs were not often used as arguments in the GPs' diagnostic reasoning Figure . SymptomAccording to the guidelines, a normal ECG opposes the diagnosis of CHF Table . Only onAccording to the guidelines, information about cardiac enlargement or pulmonary congestion on chest X-ray gives some support for CHF if there are any pathological findings, and is of some importance as an argument against CHF if the findings are normal Table . Chest XEach of the 15 GPs judged 6 case vignettes, which resulted in 90 judgement situations. In 48 of them, the EF value (or the information about left ventricular function in CV3) was used as an argument for or against CHF . In three judgement situations, the final diagnosis was in the same direction as the X-ray argument (three CHF). In seven judgement situations, the GP was uncertain about the diagnosis.In our study, the GPs used other diseases as an argument in a total of 70 judgement situations, mostly as arguments for CHF (91%). Atrial fibrillation, emphysema, history of myocardial infarction, and hypertension were the diagnoses most commonly used in this way.For certain variables, the same information value was used by some GPs as an argument for and by others as an argument against CHF. The presence of emphysema was sometimes seen as increasing the risk of CHF , or as an alternative explanation for symptoms .Diabetes could also be seen as increasing the risk of CHF , or as an alternative explanation for symptoms (e.g. GP 1, CV5: "... we have to improve her diabetes, since her fatigue may be due to that.").Advanced age could be seen as increasing the probability of CHF (e.g. GP 2, CV6: "He's the age for it!"), or as an alternative explanation for symptoms . Age was used as a diagnostic argument only for the two patients over 80 years of age.For relative cardiac volume, the reasoning could be compatible with GPs using different threshold values in their reasoning. The two lowest values were only used as arguments against CHF, the two highest values only as arguments for it, and the two intermediate values were used as arguments in both directions.There was total agreement among the GPs only for the prototypical CHF case; otherwise there was a large variation among GPs regarding diagnoses. Case vignettes representing CHF patients were more likely to be correctly diagnosed than those representing non-CHF patients Table .When comparing the GPs' diagnostic reasoning with guidelines, we found that the clinical information in the case vignettes was not used to the extent recommended in the guidelines. It is true that information about the ejection fraction value on ECHO was the single most frequent diagnostic argument, and it was the most common argument against CHF. This is in line with the guidelines, which emphasize the need for objective evidence of cardiac dysfunction. However, in more than one third of the judgement situations, the information about ECHO that was presented was not used as an argument. Over-diagnosis of CHF in primary health care has been demonstrated in a number of studies, with ECHO findings as the gold standard ,4,15. LiIn the diagnostic algorithm, symptoms and signs are the entry criteria. However, the GPs did not seem to use them consistently in this way, except when diagnosing the prototypical CHF and non-CHF cases. One reason for this might be that most symptoms and signs considered typical for CHF are fairly non-specific as regards the diagnosis CHF.Information about other relevant diseases, which was important in the GPs' diagnostic reasoning, is not included in the list of assessments to be performed routinely Table  9]. How. How9]. The case vignettes represented authentic patients referred by GPs to a cardiology department for problems related to heart failure. This may have led to a selection of more complicated patients than the "typical" heart failure patients in primary health care. The reason we chose this group of patients was that we wanted to include patients who were thoroughly investigated, with a well-founded clinical diagnosis, and for whom information about all variables of interest could be found in the patient records. Selecting GPs only from health care centres in, or relatively close to, the city centre may have biased the results, since differences in catchment areas, working conditions, and access to echocardiography may influence GPs' diagnostic habits. This could make it difficult to generalize the results to other GPs. Only 50% of the GPs who were contacted agreed to take part in the study, which could bias the results. However, since the age distribution was the same in the two groups, it seems unlikely that the drop-out group would differ from the study group regarding clinical experience.The full version of the guidelines is difficult to apply to individual diagnostic situations and it is also difficult to use it for assessment of diagnostic behaviour . In thisGPs' tendency to over-diagnose CHF has been explained by their relying on symptoms, signs and less specific investigations such as chest X-ray, and by limited access to ECHO in the primary health care. However, this study indicates that a substantial minority of GPs seem to be less familiar with the use of ECHO and EF. Thus, access to ECHO ought to be accompanied by education about how to integrate this information better in the diagnostic reasoning.Guidelines ought to include search of information about other cardio-vascular diseases in the list of assessments to be performed routinely Table  and in tThe information in the case vignettes was underused as arguments for and against the possibility of CHF as compared with the guidelines. Information about the EF value was the single most frequently used argument for or against CHF; nevertheless, in one third of the diagnostic judgements the GPs did not consider any information about the ECHO in their diagnostic reasoning. Information about symptoms and signs were not used to to the extent suggested in the guidelines. Information about other relevant diseases was frequently used in the GPs' diagnostic reasoning, indicating that they often relied on illness scripts. Some implications of our study are that 1) GPs should be taught how to use ECHO information better in their diagnostic reasoning, 2) guidelines ought to give more importance to information about other cardio-vascular diseases in the diagnostic reasoning, and 3) guidelines ought to treat the topic of diastolic heart failure in a clearer way.CHF Chronic heart failureCOPD Chronic obstructive pulmonary diseaseECHO EchocardiographyECG ElectrocardiographyEF Ejection fractionGP General practitionerThe author(s) declare that they have no competing interests.All authors conceived of the study and participated in the design. YS carried out the data collection, performed the statistical analyses and drafted the manuscript. All authors participated in the interpretation of the results and the discussions of the drafts. All authors read and approved the final manuscript.The pre-publication history for this paper can be accessed here:Case vignette characteristics The additional file shows some important characteristics of the case vignettes. Format: Word-table.Click here for file


No two countries have adopted identical regulatory measures on cloning. Understanding the complexity of these regulatory variations is essential. It highlights the challenges associated with the regulation of a controversial and rapidly evolving area of science and sheds light on a regulatory framework that can accommodate this reality.Using the most reliable information available, we have performed a survey of the regulatory position of thirty countries around the world regarding the creation and use of cloned embryos (see Table While most of the countries studied have enacted national legislation, the absence of legislation in seven of these countries should not be equated with the absence of regulation. Senator Morin was not correct in stating that the majority of recent legislation bans both RC and NRC. Recent regulatory moves are united only with regard to the banning of RC. While NRC is not permitted in seventeen of the countries examined, it could be permitted in up to thirteen countries.There is little consensus on the various approaches to cloning laws and policies, and the regulatory position in many countries remains uncertain. Now, a  history , it is a history ,5 – partfunctional embryos, whether by nuclear transfer or embryo splitting. As this suggests, we will use 'embryo' to refer to any human entity considered theoretically capable of implantation and development in the womb. Many regulatory positions distinguish between the creation of a cloned embryo for reproductive purposes and for other purposes. For our purposes, the former will be called reproductive cloning (RC for short) and the latter non-reproductive cloning (NRC for short). This paper will examine the regulatory position of the thirty countries for which we have been able to obtain reliable information  and the United Nations. Section VI will explain why the regulatory outcome usuallysays little about the ethical approach adopted by a particular jurisdiction. Section VII is the conclusion.As many commentators have noted, there is great variation in regulatory approaches even within countries that have decided to create relevant laws and policies ,5,7,8. NThe majority of the countries studied have now enacted national legislation  have many jurisdictions, each capable of adopting a different regulatory position. Given the superficial similarity of many of these countries and jurisdictions, it is hard to explain such stark variation on cultural differences alone [NRC represents the source of considerable regulatory variation. While NRC is not permitted in seventeen of the countries studied, it could be permitted in es alone ,10.Only Belgium and the UK have deliberately enacted or extended legislation for the purpose of permitting the creation of cloned embryos for research ,11. The In contrast, Finland, Greece, Israel, Russia and Sweden appear to allow NRC only because their legislation has potential gaps . The Gre"only reproductive cloning is prohibited. It could be thus construed that therapeutic cloning is permitted....This position has also been supported in the Report of the National Bioethics Committee regarding the use of stem cells in biomedical research and clinical practice (21.10.2001), submitted to the Prime Minister on 11.1.2002."This is nonetheless controversial in Greece, which has ratified both the European Convention on Human Rights and Biomedicine, and its Additional Protocol on cloning (discussed below).The US, India, and Portugal are anomalous. In the US, what little national legislation there is only concerns the use of federal funds  and someThere are, of course, many nations that have long standing laws that are relevant to cloning technologies. In many of these nations, however, the laws were designed prior to Dolly and the recent advances in stem cell research. As such, how these laws might apply to cloning is sometimes unclear. Also, these laws are not a result of a public and political dialogue about the complex scientific and ethical issues that are associated with cloning and stem cell technologies.  In additin vitro embryo, contains a diploid set of chromosomes obtained from a single – living or deceased – human being, foetus or embryo". This clearly captures SCNT.The legislation of some countries clearly encompasses somatic cell nuclear transfer (SCNT). The Spanish Law 35 of November 1998 is an example of a pre-Dolly legislation of this type. This Act not only renders it an offence to create identical human beings where it is aimed at race selection, it also renders it an offence to create "human beings by cloning in any of the variants or any other procedure capable of originating several identical human beings." The Canadian Assisted Human Reproduction Act 2004 is an example of post-Dolly legislation of this type. Under this Act, the creation and implantation of a "human clone" are prohibited. "Human clone" is defined under s. 3 to mean "an embryo that, as a result of the manipulation of human reproductive material or an In a number of contrasting countries, SCNT is only captured by a broad, non-literal interpretation of the relevant provisions. The Swedish Law No. 115 of 14 March 1991 is an example of pre-Dolly legislation of this type. This Act only regulates experiments performed on "fertilised ova" or gametes "before fertilisation". The Finnish Medical Research Act 1999 is a rare example of post-Dolly legislation of this type. This Act has many provisions with respect to research on embryos (including a prohibition on the creation of embryos for research) and it prohibits all research conducted with the aim of cloning a human being. However, s. 2 of the Act defines an embryo as "a living group of cells resulting from fertilisation not implanted in a woman's body". Thus, the Dolly technique only appears to be covered insofar as its use involves "research with the aim of cloning human beings" (Also, s.1 of the Constitution secures the inviolability of human dignity, but there is no authoritative interpretation on whether (and how) this provision could apply to cloning). If this aim is only correctly attributed to RC, then NRC might not be covered at all.in vitro embryos. More precisely, the Act imposes a licensing requirement on the creation of an in vitro embryo (ss.3(1)(a) and 1(2)); storage or use of in vitro embryos (ss.3(1)(b) and 1(2)); storage of gametes (s.4(1)(a)); and use of gametes, unless 'services are provided for the woman and man together' (s.4(1)(b)). Yet, under s. 1(1) of the Act, "embryo" is defined as "a live human embryo where fertilisation is complete", including "an egg in the process of fertilisation". This raised the question of whether SCNT fell outside the Act altogether. Nonetheless, the House of Lords recently held that SCNT produces a functional embryo that falls within the ambit of this Act (in effect, holding that the Act's definition of embryo is non-exhaustive and restricted in purpose) [The dangers of non-literal interpretation of pre-Dolly provisions should not be exaggerated. Although there are a number of countries that have such legislation (notably, Austria and Germany and, until very recently, France) , in realpurpose) .Not only is there a great deal of variation between nations and much uncertainty as to the scope of existing laws, many of the existing laws and policies are in a state of flux. Indeed, some countries have built in review provisions.The Dutch legislation, the Embryo Act 2002, presents an example. This Act prohibits procedures undertaken for the purpose of creating genetically identical human individuals and prohibits the creation of embryos for research. Yet, s. 33 of the Act allows for the future repeal of the prohibition on the creation of embryos for research. Likewise, the recently enacted Canadian legislation states that a Parliamentary review of the law is required within three years of proclamation.for a period of 5 years, no intervention will be carried out on human cells for the purpose of human cloning or to bring about the creation of a person by the use of reproductive cells that have undergone permanent intentional genetic modification [Some countries, such as Israel, New Zealand and Russia, have even adopted time-limited legislation. The Israel legislation of 1999, for example, states that, and to explicitly allow somatic nuclear transfer as a way of creating embryos for non-reproductive purposes. Thus, Sweden is likely to join Belgium and the UK in permitting NRC by legislation.Other countries are in the process of considering a revision to their existing law. Ireland has set up a Commission on Assisted Human Reproduction in 2000 to explore this topic . There aThe European Convention on Human Rights and Biomedicine has now been signed by 31 of the 45 member States of the Council of Europe, of which 15 have also ratified the Convention . It has functional human embryos for research. While the Convention makes provision for referrals of questions of interpretation to the European Court of Human Rights (Article 29), referral is unlikely because the Convention arguably leaves such decisions to the discretion of individual States. The Strasbourg court itself allows individual States a wide discretion (known as the 'margin of appreciation') in controversial policy areas. The court has, for example, adopted this approach when considering whether the fetus is included in the provision of the European Convention on Human Rights and Fundamental Freedoms that grants 'everyone' a right to life (see the latest case: Vo v France (no. 53924/00)). Moreover, before signing or ratifying the Convention on Human Rights and Biomedicine, any State could make a reservation to this provision insofar as it is inconsistent with their pre-existing law (Article 36). This is what we would expect the UK to do if it eventually signs the Convention.Article 18(2) of the Convention prohibits the "creation of human embryos for research purposes". The phrase "human embryos" is not defined by the Convention and subsequent negotiations of the working party on the protection of the human embryo and fetus appear to have failed to reach agreement on this and other issues. This provision only prohibits NRC if it captures the creation of all Whether RC is implicitly prohibited by the Convention is more controversial. Those who hold that cloning violates human dignity will no doubt point to Article 1, which requires parties to the Convention to "protect the dignity and identity of all human beings". This seems tenuous. There is, however, an Additional Protocol on the Prohibition of Cloning Human Beings . ArticleAny intervention seeking to create a human being genetically identical to another human being, whether living or dead, is prohibited.Since "genetically identical" is defined, under Article 1(2), as "sharing with another the same nuclear gene set", use of the Dolly technique on humans is included within this prohibition. This provision clearly captures RC. What is more controversial is whether it covers NRC. To foreclose this possibility, when the Dutch government signed the Protocol it added an interpretative statement declaring that it "interprets the term "human beings" as referring exclusively to a human individual, ie a human being who has been born". This interpretative statement is arguably unnecessary, because, in the absence of a definition of human being in the Convention itself, States are free to interpret this provision in accordance with their own national policy.The impact of these international instruments is particularly important with regard to the three countries that have ratified both: Portugal (which has no legislation), Greece (whose legislation only explicitly prohibits RC), and Spain (which has comprehensive legislation in this area). In Greece, the Explanatory Memorandum to the legislation declares that ' [i]t could be...that therapeutic cloning is permitted exactly as in Article 1 paragraph 1 of the Additional Protocol on Cloning'. We understand that conservative opinion is of the view that this interpretation is in conflict with Article 18(2) of the Convention itself. However, neither the Convention nor the Protocol on Cloning provide any sanctions for violation.The United Nations' struggle to agree on a cloning treaty exemplifies both the variation of approaches and the challenges associated with seeking consensus in a morally contested area . In DeceThere has, however, been little consensus on how to proceed. Though all countries agree that RC should be banned, there is deep division regarding NRC. Neither the Ad Hoc cloning committee nor the UN's Legal Committee could reach a consensus on which proposal to support and bring before the General Assembly. In November 2003 the Legal Committee voted (80-79) to recommend a two-year deferral on a General Assembly decision – a compromise that was put forward and supported by most of the members of the Organization of the Islamic Conference. This decision was largely seen as a victory for those countries supporting a more permissive approach to cloning policy . Indeed,The fact that the deep division at the UN is primarily about NRC reflects the lack of any consistent approach to cloning policy. For example, one would expect an emerging trend toward the banning of NRC, as suggested in the quote by Senator Morin, to be reflected in the building of consensus or, at least, a degree of flexibility at the UN General Assembly.Few areas of regulation are as evidentially driven by ethical views as the regulation of cloning and cloning research. This is not the place for in-depth analysis of the underlying debate. Elsewhere we have both argued that existing regulatory attempts to prohibit RC have rarely been underpinned by thoughtful exposition of underlying ethical principles ,10,34. PLawyers rarely look to regulatory outcome to understand ethical debates. Unfortunately, in the area of cloning many commentators do that very thing. As our starting quotation demonstrates, politicians and commentators are all too ready to find support for their ethical views in regulatory positions adopted elsewhere. There are, however, varying levels of ethical agreement. Agreement on the appropriate regulatory position does not imply agreement on the underlying ethical principles.full status position would grant the embryo the same level of moral duties as you or I. The no status position would grant the embryo no more status or dignity than your hair or nails. The limited status position would grant the embryo a fixed or gradualist level of intrinsic moral value between these two extremes. The full status position will require the prohibition of NRC (destructive use of embryos is considered murder) and the no status position will usually require NRC to be permitted . The limited status position is, however, potentially compatible with either regulatory position, depending on the particular status given to the early embryo and the weight given to potential benefits of NRC. It follows that the fact that the regulatory position permits or prohibits NRC does not do even tell us what status the embryo is considered to have. This is further complicated by the fact that supporters of the no or limited status position might be prepared to accept more restrictions than are strictly required by their position to protect a more important moral goal. Only supporters of the full status position cannot coherently make such pragmatic compromises [Consider the relationship between ethical positions on the moral status (or dignity) of the cloned embryo and NRC. The cloned embryo could be considered to have full, no, or limited moral status ,35. The promises .Similarly, the existing positions on RC could be supported by radically different ethical views. Prohibitions could be supported by those who hold that RC is absolutely wrong  and by those who hold that cloning at present would be wrong. Even time-limited prohibition does not enable us to discern whether it is underpinned by, for example, the view that RC is wrong because of current safety issues or the view that RC is not wrong but the most effective way to get there is by initially prohibiting it.In sum, the majority of regulatory outcomes could be coherently explained by reference to one or more underlying ethical positions. Thus, similar or even identical regulatory outcomes imply less by way of ethical agreement than some may be inclined to believe.Cloning laws and policies are far from uniform across the globe and the legal position in some countries remains uncertain. This will give little comfort to scientists and policy makers hoping to gain clear direction from the international position. For the time being at least, policymakers must accept the reality of international "dissensus" and scientists wishing to undertaken research on NRC are best advised to consider conducting their research in only a handful of countries. Even where there is agreement as to the regulatory outcome, policy-makers should not confuse this with agreement on underlying ethical principles. Like many topics concerning the developing genetic and reproductive technologies, cloning remains controversial.The author(s) declare that they have no competing interests.Both authors contributed to the original concept for the paper, the writing and revision of the manuscript and the analysis of the law.The pre-publication history for this paper can be accessed here:


Multivariate imaging techniques such as dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) have been shown to provide valuable information for medical diagnosis. Even though these techniques provide new information, integrating and evaluating the much wider range of information is a challenging task for the human observer. This task may be assisted with the use of image fusion algorithms.Kernel Principal Component Analysis (KPCA) is proposed for the first time. It is demonstrated that a priori knowledge about the data domain can be easily incorporated into the parametrisation of the KPCA, leading to task-oriented visualisations of the multivariate data. The results of the fusion process are compared with those of the well-known and established standard linear Principal Component Analysis (PCA) by means of temporal sequences of 3D MRI volumes from six patients who took part in a breast cancer screening study.In this paper, image fusion based on The PCA and KPCA algorithms are able to integrate information from a sequence of MRI volumes into informative gray value or colour images. By incorporating a priori knowledge, the fusion process can be automated and optimised in order to visualise suspicious lesions with high contrast to normal tissue.Our machine learning based image fusion approach maps the full signal space of a temporal DCE-MRI sequence to a single meaningful visualisation with good tissue/lesion contrast and thus supports the radiologist during manual image evaluation. As a consequence, analysing multivariate images in radiology remains a time consuming and challenging task which potentially can be alleviated by the application of is the combination of two or more different images to form a new image by using a certain algorithm' e.g. integration of a large number of multivariate images from a remote sensing process into one image. Because Genderen & Pohl already stated PCA as a standard technique for image fusion in remote sensing, we adopt the more general definition of the term image fusion from the remote sensing community. Whereas in the medical imaging community the meaning of the term image fusion is commonly restricted to fusion of multimodal images, the definition of this term used in this article also includes multivariate images such as multispectral or multitemporal images.Image fusion methods have been an area of research for several decades. According to Genderen & Pohl ,10, imagartificial neural networks (ANN) have gained much attention from the remote sensing community [dimension reduction: Ignoring the spatial order of the patterns x, the image data is an unordered set of patterns that forms a data distribution in the data space  and image fusion or dimension reduction corresponds to a mappingPattern recognition methods such as ommunity -15. From which retains certain properties of the original data distribution. Subsequently, the mapped patterns  can be spatially ordered according to the locations p of the corresponding sources, leading to the final fused images.to a new low dimensional space Principal Component Analysis (PCA) [Self Organising Maps [. Hence, they are especially suited if  is high dimensional.Well-known algorithms such as is (PCA)  or Self ing Maps  have beeing Maps -15. It iKernel PCA (KPCA) which was proposed by Schölkopf et al. in 1998 [In this work, we investigate the application of machine learning algorithms to medical image fusion. We compare the results of the standard linear PCA with it's nonlinear extension, the so called  in 1998 . Our emp in 1998 .principal directions (PDs), by optimising a certain criterion. The mapping M is defined by a subset of all possible PDs. Projecting each pattern xp on to one of these PDs associates each spatial position p with a new scalar value   of which integrates information from the different components  of xp, respectively. The resulting 3D image can be visualised as a gray value image or using perceptually optimised colour scales [ of the patterns can be displayed as RGB composite images, if M is defined by a set of three PDs.In the following, we briefly describe the theoretical background of the linear PCA and nonlinear KPCA algorithms and their application to the task of image fusion. Both methods determine a set of projection directions, referred to as r scales ,22. Altexi}, xi ∈ , 0 ≤ i ≤ N, PCA is a transformation in a new coordinate system of uncorrelated and orthogonal principal axes ξ ∈ , |ξ| = 1 which can be derived from the eigenvectors of the covariance matrixPrincipal Component Analysis is one of the most frequently used dimension reduction method. Suppose the data are given by the set Γ = {by solving the eigenvalue equationλξ = Cξ     (2)λ ≥ 0 and ξ ∈  \ {0}. The first eigenvector ξ1  maximises the variance . Therefore, the set of the first n ≤ d eigenvectors or PDs carry more variance than any other n orthogonal projections.for Principal Component Analysis or Fisher Discriminant Analysis with nonlinear kernel functions [In recent years, kernel based methods have been the object of much research effort within the machine learning community. The concept of a subset of kernel methods is based on the combination of well-known linear algorithms such as unctions ,24. WhilConsider a nonlinear functionx ∈ Γ to some feature space [. In order to perform the PCA in , one has to find the eigenvectors ξ of the covariance matrixwhich maps the examples re space . Further with ξ ∈  \ {0} and λ ≥ 0. Substituting (3), it is easy to see that the eigenvectors ξ lie in the span of Φ(x1),...,Φ(xN). Therefore, Schölkopf et al. [i.e. those vectors that satisfy f et al.  define tNλα = Kα    (4)α denotes the column vector of coefficients α(1),...,αN)  = Φ(xi), Φ(xj).    (6)αk corresponding to the k-th eigenvalue λk of K ensures λkαk, αk = 1. Now, principal components can be extracted in  by projecting an example x on ξk usingNormalising Φ(xi), Φ(xj) is needed rather than the explicit images Φ(xi), Φ(xj) alone. Instead, one can use kernel functions fulfilling Mercer's Theorem such as the Gaussian KernelIt is crucial to note that for extracting principal components using (4) and (7) the inner product σ or the Polynomial Kernel of degree dwith bandwidth parameter K(xi, xj) = xi, xjd     (9) to be performed implicitly with reasonable computational costs. For the Polynomial Kernel we have a clear interpretation of KPCA. In this case,  is the space of all monomials of degree d of the pattern components. Thus, KPCA is a linear PCA of the corresponding high order statistical features. The KPCA algorithm can be summarised as follows:which allow the PCA in the corresponding K of Γ using a suitable parameterised kernel function.1. Calculate the Gram matrix K according2. Transform . This transformation implicitly moves the centre of mass of the mapped data {Φ(xi)}, xi ∈ Γ to the origin of , i.e. centres the data in .with αk, i.e. the eigenvectors of  and normalise them.3. Calculate the eigenvector expansion coefficients 4. Extract principal components using (7).d PDs in case of PCA and up to N PDs in case of KPCA. In general, a compact visualisation of the complete data as a single image is desired. In this case, inspection of the fused image based on the PD corresponding to the first (largest) eigenvalue is optimal in terms of a general compression scheme: The projection on this PD retains most of the total data variance and leads to a reconstruction with least mean square error. Nevertheless, image fusion is commonly employed with a well defined intention e.g. in order to detect a specific phenomenon such as bushfires in multitemporal satellite images [K can be varied leading to alternative mappings to the feature space, changing the characteristic of the fusion image.Application of both image fusion techniques leads to a set of up to e images  or (as iS1,...,S6) which were taken during the the MARIBS breast screening study [p in the 256 × 128 × 64 (1.33 mm × 1.33 mm × 2.5 mm) sized volume is associated with a pattern , d = 7 describing the temporal signal kinetic of the local tissue.In the following, the fusion results of both methods are discussed and illustrated with DCE-MRI sequences from six cases .Following the first criteria, the purpose of the visualisation is specified implicitly by the voxel labels. In the present work, the expert marked regions of tumour tissues. Thus, optimal fusion images of an image sequence display locations of cancerous kinetic signals with high contrast to normal signals.receiver-operating-characteristic (ROC) analysis [Next to the visualisation of the fusion images as gray value and RGB images, both methods are evaluated by means of a analysis ,28. To tHowever, no conclusion can be drawn about how well other tissue types are distinguishable in the fusion images, i.e. how well the information of the entire signal space is represented.d image volumes of each sequence. To ensure this normalisation is robust with respect to single outlier values, the values are calculated based on an application of a 3 × 3 × 3 median filter.For numerical reasons, the voxel value range of each volume sequence is individually normalised to [0; 1]. In order to preserve the signal kinetics, the individual minimal and maximal intensity value is determined simultaneously on all sum of local intensity differences (sod) featureSince about 66% of each volume is covered by background, all images sequences are preprocessed with a full automatic tissue/background separation method. The histogram of the closing operator [individually calculated for each sequence, has a bimodal shape and shows a clear separable maximum for the background voxels. The optimal threshold separating background from tissue can be computed automatically . The resoperator  to ensurIn order to automate and optimise the fusion process, a priori knowledge about the phenomenon to be visualised, given by the expert label, is used to find a suitable parameterisation of the algorithms as described in detail in the following section. In practice, these labels are not available for new image sequences. Thus, the algorithms have to be adapted on a small number of image sequences, e.g. from a subgroup of cases of a screening study, which were manually evaluated by a human expert and can be subsequently applied to the data of an arbitrary number of unseen cases.To assure the experimental setup reflects the circumstances of a practical application, the data sets Γ used for adaptation consist of marked tissue signals from only five of the six image sequences and the sixth unseen image sequence is used for the evaluation of the algorithm's capabilities. This setup is repeated six times, each time using a different image sequence for evaluation. In case of KPCA, using all kinetic signals from the five image sequences is prohibitive due to the computational and memory complexity. Therefore, the KPCA is adapted with a reduced data set Γ consisting of all signals of the marked tumour regions and an equal number of signals randomly selected from non-tumour regions. to the feature space  by the kernel function. In this paper, we focus on the frequently used Gaussian Kernel (8) which is parameterised by the bandwidth parameter σ. Selection of this parameter is crucial for the fusion process. For the experiments, s is chosen by scanning the range [0.05,...,2.0] using a step size of 0.05. Because manual evaluation by visual examination of the fusion images of each parameterisation is time consuming, we apply an automatic selection heuristic for the bandwidth based on the component specific Fisher scoreAn essential part of kernel methods is the mapping from the data space μ± and variance v±. The Fisher score is commonly used for ranking components xk) (of a set {(x, y)} of binary labelled (y = ±) examples according to their discriminative power. In a similar manner, the score can be evaluated for different PDs on a random subset of the training set Γ utilising the corresponding principal component values with their associated expert label and thus can be interpreted as a measure for the first evaluation criteria. Furthermore, the sign of the PCA/KPCA based PDs can be adjusted in order to obtain a high value for the average intensity of tumour voxels causing tumour lesions to appear as bright regions.with class specific mean Thereby, the a priori knowledge of which region of the five image sequences used for adaptation should be visualised with high contrast can be utilised for selecting proper parameterisations which lead to discriminative visualisations tailored to the given task.I1, I2 and I3. For the purpose of visualisation, the range of the voxel values is normalised to [0; 255]. Additionally, I1, I2 and I3 are composed in to an RGB image IRGB. For fusion images based on KPCA, the bandwidth for each Ik is chosen according to the individual maximum of the Fisher criterion as illustrated in Fig. For each method and image sequence, the first three PDs are used for calculating fused images, referred to as S1,...,S6 based on the PCA algorithm are shown in the lower 2 × 2 block of Fig. I1 based on the PD with the leading eigenvalue does not lead to discriminative visualisations. The tumour lesions appear with the same intensity as fatty tissue, while glandula tissue is displayed as dark areas (S3, S4). In contrast to I1, the discriminative power of I2 is obviously much greater for all six image sequences. The display of the tumour lesions  differs significantly from areas of glandular tissues, blood vessels  and fatty tissue . The contrast between tumour lesion and the surrounding tissue decreases in I3 of S2, S3 and S5. Additionally, the surrounding tissue is displayed less detailed (S1, S2, S4, S5). According to the weak discriminative characteristic of I1 and I3, the tumour lesions are coloured with shadings of green or cyan in the corresponding IRGB.Fusion results for the sequences S1, S2, S3 and S4, image I1 displays the tumour lesion with high contrast to the surrounding tissues. Adipose tissue appears in I1 and I2 with mediumin tensity. In I2 of S4 and S3, glandular tissue can be observed in addition to the tumour. These areas appear dark in I1. The fraction of glandular tissue regions in I2 of S1 and S2 is much smaller, since the tumour is located near the chest muscle where the breast mostly consists of fatty tissue and blood vessels.Fusion images based on KPCA are shown in the upper 2 × 2 block of Fig. I3 of S4. The image clearly shows a ring structure as part of or around the tumour lesion. At positions inside the ring which are displayed with high intensity values in I1 and I2, the temporal kinetic patterns show a fast uptake with a following constant or slightly decreasing concentration of the contrast agent. In contrast to the signals inside the ring, all signals corresponding to the ring structure in I3 show as teadily increasing concentration. In all composite images IRGB except for S5, the tumour lesions are coloured white and can be easily discriminated from fatty tissue (shadings of blue to purple) and glandular tissue (shadings of blue to green). For image S5, only I1 shows a discriminative characteristic. The tumour is displayed as a small cluster of high intensity values in the lower right area of the right breast, next to the implant.An interesting detail can be observed in I1, I2 and I3 are compared by measuring the area-under-the-curve(AUC) values. The corresponding AUC values are listed in Tab. PCA in Tab. I2 based on the second PD of the PCA algorithm significantly outperforms the corresponding PCA based fusion images I1 and I3. A similar predominance of I2 can be observed for the KPCA based AUC values (column KPCA in Tab. I2 outperforms I1 and I3 in four of six cases (S1, S2, S3 and S5). Only for S4 and S6 the fusion image I1 yields the largest AUC value. Nevertheless for KPCA, the difference to the corresponding fusion images I1 and I3 is much less distinct. In particular I1 yields AUC values which are close to those of the corresponding fusion image I2. The predominance of the second component also decreases, if the PCA algorithm is trained with the reduced data set used for adaptation of the KPCA (column PCA (reduced) in Tab. I2 decrease and increase for the fusion images I1 and I3.According to common practice, the curves obtained from the ROC analysis of the fusion images σ on the fusion characteristic is illustrated in Fig. σ only a small fraction of the tumour lesion appears with high intensities. If the bandwidth is chosen according to the maximum of the Fisher score, the lesion is visualised with high contrast to the surrounding tissue. In the shown example, the Fisher criterion decreases along with the contrast of the visualisation for further increasing bandwidth values.The influence of the bandwidth i) The sign of the PD is selected in a way that tumour lesions always appear with high intensities. (ii) The parametrisation of the kernel function of the KPCA is optimised in such a way that the fusion images show the desired discriminative characteristics. Thus, both evaluation criteria stated in the section Evaluation criteria are accomplished.The results shown in the preceding section indicate that fusion of DCE-MRI data by PCA or KPCA leads to compact and meaningful visualisations. Lesions are correctly displayed as bright regions or with specific colouring and can be easily discriminated from surrounding tissue. Once a small subgroup of cases is evaluated, the obtained secondary information in the form of labelled tumour areas is utilised for automation of the data processing and presentation: . However, selection of a suitable kernel parametrisation leads to comparable AUC values for I1. For fusion images corresponding to PDs with smaller eigenvalues, KPCA based images still show more details than those based on PCA, if the bandwidth value is chosen according to the maximum of the Fisher score. Figure I4, I5 and I6 for sequence S4. While KPCA distributes the total data variance on N PDs, the PCA method uses only d PDs. Therefore, the PCA based fusion images I4, I5 and I6 typically contain a large fraction of high frequent noise. It is important to note that the fusion images based on KPCA are not necessarily uncorrelated, if each image is calculated using PDs with different bandwidth values, and therefore may display redundant information. In five of six cases, RGB visualisations based on KPCA show the tumour lesion as white regions which are easy to discriminate from other tissue types. In contrast to subtraction images which also allow detection of lesions with high sensitivity  for the adaptation, i.e. calculation of the kernel matrix and extraction of 3 PDs, increases significantly with the size of the training set Γ and takes 73 seconds for Γ consisting of 2700 training items which is comparable to the computation time of the PCA for the given setup (see Fig. One drawback of KPCA is the increased computational and memory complexity in contrast to PCA. In case of KPCA, the complexity scales with the size see Fig. . While esee Fig. .d-dimensional vectors and the calculation of the three fusion images I1, I2 and I3 of one volume slice takes approximately 1 second. In case of KPCA, the inner product has to be calculated in the feature space and the PD in  is only implicitly given as an expansion of N kernel functions. Thus, computation of I1, I2 and I3 of one volume slice takes approximately 23 seconds for training sets Γ consisting of 1000 examples and increases linearly with the size of Γ (Fig. More important for practical applications of both methods is the computational expense for calculation of the fusion images. Using PCA, the value of a fusion image voxel is equivalent to the inner product of two f Γ Fig. .In consideration of the fact that both methods are able to fuse the multitemporal DCE-MRI to single meaningful images which do not only show the lesion with high intensities, but also other types of tissue such as fatty or glandular tissue, the standard linear PCA seems to be most suitable for the given signal domain because of it's low computation time and superior detection performance. Only for PCA, the three fusion images can be calculated for a complete volume in a reasonable time and without delaying the diagnostic process. According to the ROC analysis, the introduction of nonlinearity by the kernel function did not improve the discriminative properties of the fusion images, but visual appraisal of the RGB composite images based on KPCA suggest a more comprehensive display of the different types of tissue. It is an open question whether fusion images of other data domains with more complex or higher dimensional signals might benefit more obviously from the nonlinearity of KPCA.In this paper, we have demonstrated the integration of distributed information from DCE-MRI image sequences to meaningful visualisations by means of PCA and KPCA. Both methods were able to accentuate the regions marked by the expert as important in image sequences blinded to automatic analyses. By the employment of task-specific information, the parametrisation of the KPCA algorithm was optimised in order to accentuate the relevant characteristics of the visualisation.PCA Principal Component AnalysisKPCA Kernel Principal Component AnalysisPD Principal DirectionDCE-MRI Dynamic Contrast Enhanced Magnetic Resonance ImagingT. Twellmann, A. Saalbach and T. W. Nattkemper conceived the experimental setup. Implementation and realisation was done by O. Gerstung. Image acquisition was done under supervision of M. O. Leach.