Background: Experienced clinician educators readily identify trainees with diagnostic reasoning difficulties but often lack training to diagnose and remediate errors. Taxonomies of cognitive causes of diagnostic errors can inform remediation, but clinician educators need simple tools to identify, record, report and provide feedback on these errors. A checklist may help achieve these goals. Objectives: To characterise the cognitive contributions to diagnostic errors (CCDEs), trainees make in patient encounters, with the view to develop training and remediation programmes for medical residents preparing for specialist examinations. Secondly, to determine examiners’ perceptions of a checklist in order to document and provide feedback on CCDEs to unsuccessful candidates and trainees making diagnostic errors in examinations, on ward rounds and during bedside teaching activities. Methods: Thirty examiners used a 17-item checklist to identify and record CCDEs made by medical residents failing patient encounters in a national specialist examination. A survey was used to explore examiners perceptions of the checklist to document and provide feedback on these errors. Results: Ninety-eight of 264 patient encounters were failed (37%). Ninety-four completed checklists documented 691 CCDEs (median of 7 per encounter). Cardiac (28.7%) and neurology patients (18.1%) constituted approximately half of the failed encounters. By category: data synthesis was more problematic than data gathering, faulty knowledge or data interpretation (35.2% vs. 25.8% vs. 21.9% vs. 17.1%); χ2=48.2, (p<0.0001 for all comparisons). The 'top five’ individual CCDEs were failure to elicit history and/or examination findings; poor knowledge of clinical features (illness scripts); case synthesis (putting the case together) and misinterpretation of clinical findings. History and physical examination-related errors accounted for 60% of the 'top 5’ CCDEs, Examination-related errors were more common than history-related errors (p<0.0001). The survey of the checklist was completed by all (30) examiners. Seventy-three percent finished the checklist in less than five minutes, describing it as comprehensive and easy to use. The majority (96.7%) thought the checklist could be a better way of providing structured feedback to unsuccessful candidates. Most examiners (93.3%) considered it a useful way of guiding bedside teaching for residents preparing for specialist examinations, and 76.7% thought it could improve feedback on CCDEs to unsuccessful candidates and guide remediation and training. Conclusion: A 17-item checklist identified three priority CCDEs which require focussed remediation and training in South African medical residency programmes: improving clinical skills, developing adequate illness scripts and 'putting a case together’. This does not require extensive pedagogic expertise but rather use of a simple tool to provide customised feedback, remediation and faculty support. We showed that the simple checklist used in this study helped clinician-educators/examiners without pedagogic expertise to diagnose and record CCDEs contributing to poor performance in high stakes examinations. Examiners endorsed the use of the checklist and its potential to improve feedback and training addressing CCDEs made by trainees at the bedside.

The work of the gas transmission pipeline system is regulated by the thousands of valveses and other elements of the shut-off valves, located in different places. Information about the current status of each valve, and confidence in its technical serviceability is an important element in the control of pipeline system. There are a number of problems that adversely affect the  valving operation. Principal among them - is the lack of siystematical approach in valving diagnostics. To solve this problem, developed a new approach to the valving diagnostics – multi-level diagnostics. Depending on the level of diagnosis, we get a different amount of information about the object.   The focus is on the 3rd level of diagnosis, which allows to determine the leackages of valves, and identify type of defects quantitatively. This level of diagnosis is regarded as an example of Method «Micropuls». The method «Micropuls» based on the theory of mechanical vibrations and forced with high accuracy to set the time, frequency and spectral characteristics of noise in the details of the valve, and their spatial location and intensity of that in the presence of a system of analysis allows to determine the state of the object, its faults and defects. Micropulse technology is based on the impact on the measured object micropower impulses, records the response and subsequent filtering, decoding and analyzing the data.                    Specially designed calibrated pulses can effectively influence the measured objects (valve) over a wide range of structural dimensions and mounting schemes, regardless of physical location of the valve.

No description available.

No description available.

This work reports three reconstruction algorithms developed to address the practical issues encountered in 3D tomography diagnostics, such as the limited view angles available in many practical applications, the large scale and nonlinearity of the problems when they are in 3D, and the measurement uncertainty. These algorithms are: an algebraic reconstruction technique (ART) screening algorithm, a nonlinear iterative reconstruction technique (NIRT), and an iterative reconstruction technique integrating view registration optimization (IRT-VRO) algorithm. The ART screening algorithm was developed to enhance the performance of the traditional ART algorithm to solve linear tomography problems, the NIRT was to solve nonlinear tomography problems, and the IRT-VRO was to address the issue of view registration uncertainty in both linear and nonlinear problems. This dissertation describes the mathematical formulations, and the experimental and numerical validations for these algorithms. It is expected that the results obtained in this dissertation to lay the groundwork for their further development and expanded adaption in the deployment of tomography diagnostics in various practical applications. / Ph. D.

Objectives: To investigate the feasibility of real-time three-dimensional (3D) echocardiographic analysis of right ventricular (RV) function in healthy dogs and to compare conventional and 3D echocardiographic (3DE) indices of RV function in dogs with various stages of myxomatous mitral valve disease (MMVD), classified per the guidelines of the American College of Veterinary Internal Medicine, to those from healthy dogs. Animals: Twenty-two healthy dogs and 56 dogs with MMVD Methods: All dogs underwent conventional and 3D echocardiographic examinations. Measurements of 3DE RV function indices including RV end-diastolic volume (EDV), RV end-systolic volume (ESV), RV stroke volume (SV), and RV ejection fraction (EF) were recorded. Measurements of conventional indices of RV function were also obtained. RV EDV, ESV, and SV were indexed to bodyweight (BW) and analyzed using commercially available software. Results: Three-dimensional RV datasets could be acquired and analyzed in all dogs. Intra- and inter-observer coefficents of variation were > 20% for all 3D RV indices. Right ventricular EDV and ESV were decreased and RV EF was increased in dogs with advanced MMVD when compared to controls. Several conventional echocardiographic indices of RV function also differed between the control group and various MMVD groups. Conclusions: Real-time 3DE RV assessment is feasible in normal dogs with acceptable intra- and inter-observer variability. Several 3DE indices of RV systolic function differ between dogs with advanced MMVD when compared to normal dogs. Further investigation is required to determine if these differences have clinical implications. / Master of Science

Computed tomography (CT) is an established diagnostic modality for evaluation of canine elbow dysplasia. However, diagnostic sensitivity for elbow abnormalities may be affected by variations in CT image quality. Currently there are no data-based recommendations for elbow CT image display parameters. The purpose of this study was to test the effect of CT display parameters on observers' diagnostic certainty for CT abnormalities reportedly associated with canine elbow dysplasia. Fifty dysplastic elbows and ten clinically normal elbows were selected for imaging. Computed tomographic image data from selected elbows were filmed in transverse, sagittal and dorsal planes, with each plane filmed in window widths of 1500, 2500, and 3500 HU. Two veterinary radiologists independently evaluated each set of images for the presence or absence of hypoattenuating MCP subchondral defects, in situ MCP fissures, discrete MCP fragments, irregularity of the radial incisure of the ulna, subchondral sclerosis of the trochlea humeri, osteochondrosis or kissing lesions, and joint incongruity. Level of diagnostic certainty for each CT abnormality was recorded for each observer using a visual analog scale system. The effect of elbow status, plane, and window on the degree of observer certainty was tested. Overall, observers demonstrated higher diagnostic certainty for normal elbows than dysplastic elbows. Observer certainty for the presence of altered subchondral density (presumed osteomalacia or sclerosis) was primarily affected by window width, whereas certainty for structural defects of the MCP, radial incisure, trochlea humeri, and joint incongruity was primarily affected by image plane. / Master of Science

This dissertation examines brain lateralization and interhemispheric asymmetry patterns found in youths with Attention-Deficit / Hyperactivity Disorder (ADHD). Prior research groups have found mixed findings with respect to left and right hemisphere alterations from ADHD subjects using structural magnetic resonance imaging. In these investigations, we propose the use of Asymmetry Index (AI), a subject-specific metric that quantifies the extent of brain asymmetry and allows each subject to serve as their own control, thus reducing variability when pooling across different sites. We compare AI metric with laterality across volumetric, surface area, thickness, morphology, and white matter measures in order to characterize the ADHD brain over the course of neurodevelopment, psychotropic therapy, and behavioral presentations. Linear mixed effects models were characterized to account for individual differences and maturation. We reproduce the findings across several regional and international data consortiums that contain both cross-sectional and longitudinal ADHD neuroimaging data. Structural asymmetry group differences were more significant than lateralized comparisons across a number of volumetric and white matter measures, confirming asymmetry is robust at detecting differences between healthy controls and ADHD brains. However, the effects of medication and behavioral phenotypes failed to reproduce significant alterations across symmetry measures. We discuss these implications in light of recent evidence of possible neuroprotective features of ADHD. Future work may investigate the extent to which these brain asymmetry differences are causal or compensatory. Although structural AI is unlikely to provide a useful biomarker for ADHD, a deeper understanding of these asymmetry patterns could lead to better profiling of the clinical diagnostics and to personalized treatments.

La sténose aortique à bas débit et bas gradient (SA-BD-BG) peut s’accompagner d’une fraction d’éjection ventriculaire gauche altérée (SA-BD-BG classique) ou préservée (SA-BD-BG paradoxale). Elles constituent un sous-ensemble de patients très difficile à caractériser. En effet, le défi chez les patients avec une SA-BD-BGest de distinguer entre une SA sévère d’une SA pseudo-sévère. L’établissement de la sévérité exacte de la SA est importante, car les patients ayant une SA réellement sévère bénéficient généralement d’un remplacement valvulaire aortique, mais sans intervention, ceux-ci auront un très mauvais pronostic. Malheureusement, les critères mesurés à l’échocardiographie au repos et à l’effort, utilisés pour détecter la sévérité de la SA selon les guides de pratique actuels, ne sont pas optimaux et par conséquent, une certaine proportion de patients ne sont pas bien diagnostiqués et ne reçoivent pas la thérapie appropriée. Il a été démontré dans notre groupe que chez les patients atteints d’une SA-BD-BG, l’aire valvulaire aortique projetée (AVAProj), mesurée à l’aide d’une échocardiographie au repos et à l’effort, est un meilleur prédicteur de sévérité de la SA et de mortalité que les critères habituels mesurés lors de l’échocardiographie au repos et à l’effort. Par contre, l’échocardiographie à l’effort ne peut être faite chez tous les patients et parfois, elle conduit à des résultats qui sont non concluants.Le degré de calcification de la valve aortique, mesuré par tomodensitométrie, est un autre paramètre utilisé pour confirmer la sévérité de la SA, mais les seuils diagnostiques et pronostiques ne sont pas encore optimisés chez les patients atteints d’une SA-BD-BG. Les hypothèses sont que l’aire valvulaire aortique projetée est équivalent au degré de calcification de la valve aortique pour 1) évaluer la sévérité de la SA et 2) pour prédire la mortalité toute cause chez les patients atteints d’une SA-BD-BG. L’objectif général de ce projet de maîtrise est de comparer l’aire valvulaire aortique projetée et le degré de calcification de la valve aortique pour évaluer la sévérité de la SA et prédire le devenir des patients atteints d’une SA-BD-BG. / Low flow, low gradient aortic stenosis (LF-LG-AS) may occur with depressed (classical LF-LG-AS) or with preserved (paradoxical LF-LG-AS) left ventricular ejection fraction. This entity is really difficult to characterize. Indeed, the challenge in this subgroup is to discriminate between a true-severe versus a pseudo-severe AS. It is important to determine the exact severity of AS, because patients with a true-severe AS will benefit from anaortic valve replacement and without intervention, their prognostic will be extremely poor. Unfortunately, rest and stress echocardiographic criteria recommended by the actual guidelines for patients with LF-LG-AS to assess AS severity are far from being optimal, and consequently, a substantial proportion of these patients stays misevaluated and may thus not receive the optimal therapy. Our group found that in patients with LF-LG-AS,projected aortic valve area (AVAProj), measured under rest and stress echocardiography, better predicts underlying AS severity and survival compared to traditional echocardiographic parameters. However, stress echocardiography is not possible in some patients and AS severity often remains indeterminate. The degree of aortic valve calcification, calculated by multi-detector computed tomography may be useful to confirm AS severity, but the optimal cut off values are not well established in patients with LF-LG-AS. The hypotheses related to this study are that projected aortic valve area is equivalent to the degree of aortic valve calcification to 1) evaluate AS severity and 2) to predict all-cause mortality in patients with LF-LG-AS. The general objective is to compare the projected aortic valve area and the degree of aortic valve calcification to evaluate AS severity and to predict mortality in patients with LF-LG-AS.

La fibrillation auriculaire (FA) est la plus fréquente des arythmies cardiaques. La FA est associée à un risque accru d’accident vasculaire cérébral, d’insuffisance cardiaque et de mortalité, constituant un problème de santé publique majeur. L’avènement de nouvelles technologies permettant une surveillance électrocardiographique a démontré une haute prévalence de FA subclinique ou silencieuse chez les patients âgés à haut risque. Récemment, plusieurs efforts et essais thérapeutiques ont été dirigés vers une identification et un traitement plus précoces de la FA chez ces patients. L’anticoagulation orale a bien prouvé son efficacité dans la prévention thromboembolique chez les patients qui présentent un haut risque thromboembolique, mais au prix d’une augmentation significative des événements hémorragiques, un risque qui s’élève régulièrement chez les patients âgés et avec une comorbidité importante. Au cours des dernières années, des nouvelles alternatives non-pharmacologiques dans la prévention thromboembolique ont été développées. La fermeture percutanée de l’auricule gauche, site de formation de la majorité (~90%) des thrombus, est progressivement devenue une alternative valable à l’anticoagulation chez des patients avec FA non valvulaire à haute risque hémorragique. L’expérience des opérateurs et les innovations technologiques ont permis une amélioration remarquable des résultats en ce qui concerne la sécurité et l’efficacité. Cependant, quelques questions restent sans réponse. Les préoccupations les plus débattues suite à la fermeture de l’auricule gauche sont la prise en charge de l’anticoagulation postprocédure et la prévention/gestion de la thrombose de dispositif. Les objectifs de ce travail de recherche sont : (i) évaluer la charge arythmique silencieuse chez des patients à haut risque à l’aide de l’utilisation de nouveaux systèmes d’enregistrement électrocardiographique prolongé, et (ii) analyser l'impact hémodynamique et thrombogénique de la fermeture percutanée de l'auricule gauche avec les dispositifs actuels et émergents. / Atrial fibrillation (AF) is the most common cardiac arrhythmia. AF is associated with an increased risk of stroke, heart failure and mortality, posing a major public health problem. The advent of new technologies for continuous electrocardiographic monitoring has demonstrated a high incidence of subclinical or silent AF in elderly high-risk patients. Recently, several therapeutic efforts and studies have been directed towards earlier identification and treatment of AF in these patients. Oral anticoagulation has proven to be effective in preventing thromboembolism in patients at high thromboembolic risk, albeit at the expense of a significant increase in hemorrhagic events; a risk that increases steadily in elderly patients with high comorbidity burden. In recent years, novel non-pharmacological alternatives have been developed for thromboembolic prevention. Percutaneous left atrial appendage (LAA) closure, site of origin of the vast majority (~ 90%) of thrombi, has progressively become a valid alternative to anticoagulation in patients with non-valvular AF at high bleeding risk. Increasing operators' experience and technological innovations have led to remarkable improvements in the safety and efficacy of the procedure. However, some issues remain unanswered or controversial. Two of the most debated concerns are post-procedural antithrombotic management and device-related thrombosis (DRT) following LAA closure. The aims of the present research study are: (i) to evaluate the silent arrhythmic burden in high-risk patients using novel prolonged continuous electrocardiographic monitoring systems, and (ii) to assess the hemodynamic and thrombogenic impact of percutaneous LAA closure using current and emerging devices.