Coronary arteries obstructed by atherosclerosis can be cleared by a balloon angioplasty accompanied by a permanent scaffolding implant ("stent"). There is, however, a 25--45% occurrence rate of excessive thickening of the treated vessel wall a few weeks post-angioplasty, leading to a re-obstruction of the vessel ("restenosis"), and recurrent symptoms. Endovascular radiotherapy, a potential preventive treatment against restenosis, can be delivered by a stent impregnated with radionuclides. The present thesis examines the local dosimetry of radioactive stents. A computer algorithm, D OSECOP, was developed based on the dose point kernel theory, to calculate the dose distribution created by a 32P-implanted stent in the surrounding vessel wall. The dosimetric significance of four parameters is also assessed, namely: (1) mechanical distortions of the stent, (2) the exact location of radionuclides on the stent, (3) the self-attenuation of the stainless steel stent, and (4) the width of the stent's struts in the calculation models.

This thesis presents the design, implementation and testing of a perfusion-weighted magnetic resonance imaging sequence that is capable of acquiring several slices at a time. Various methods of image acquisition and perfusion contrast generation are considered and tested. / The results of multi-slice acquisitions are compared with those from single-slice sequences in a variety of experiments to elucidate the effects of various imaging parameters on the measured perfusion signal. A seven slice version was implemented, and was found to give good results in the tests performed. This sequence will be useful in perfusion-based functional magnetic resonance imaging studies where the region of interest can not be covered with a single image slice.

The Radiology Department of the Montreal General Hospital was testing a digital system for gastrointestinal examinations. The goal of the study was to evaluate its potential in clinical situations, with the purpose of complementing or replacing the old fluoroscopic system available at the moment. / The core of our study was to image 18 surgical specimens with gastrointestinal pathology utilizing 3 different techniques: high resolution shielded-cabinet, the Siemens digital system and the conventional analog hard copy system. / A skin dose exposure test was conducted by the department with the purpose of assessing the benefits of both the digital and the conventional systems. / We concluded in this study that the many advantages of the digital system--lower skin exposure, image reconstruction and manipulation, fast access to images, overcome its inferior resolution as compared with the analog hard-copy generation system.

This thesis retrospectively analyzes prostate's daily motion provided by three-dimensional US localization and investigates its dosimetric impacts based on XVMC calculation which takes into account patient geometry, heterogeneity and prostate motion correction. The retrospective analysis on 32 prostate patients shows that the mean  SD displacements of prostate in the AP, SI, and RL directions are -3.3  7.9 mm, -1.1  6.4 mm, -0.2 5.6 mm, respectively. The largest rotation occurs about lateral axis with mean  SD of -0.9  4.6, ranging between -6.7 and 8.0 from a preliminary study including three patients. To assess the dosimetric impacts of prostate motion, five motion scenarios including with and without prostate translation and correction, with translation and rotation but no correction or only having translation correction are simulated. Analysis based on dose-volume histograms and isodose curves shows that prostate motion (translation and rotation) will deteriorate the dose delivered to patient target and OARs. With translation correction method, the degraded patient dose could be recovered nearly completely. For the scenarios with both translation and rotation, translation correction method could dramatically improve the degraded patient dose, but could not completely eliminate the dosimetric impact of prostate motion. Besides, the dosimetric impact of metal prosthesis in three patients has been analysed as well. Up to 5% discrepancies in their D90%, D95%, V90%, and D95% for PTV have been observed. / Le mouvement de la prostate est un problème critique dans le traitement conforme du cancer de la prostate, le plus commun cancer parmi les hommes au Canada. La radiothérapie guidée par l'image (IGRT) utilisant les images ultrasons (US) quotidiennes est une technique largement utilisée pour régler ce problème. Une nouvelle technique de localisation ultrasons en trois dimensions, basée sur une méthode de vérification intra modalités, a été testée à l'Hôpital General de Montreal en 2005. L'objectif principal de cette thèse a été de mieux quantifier l'amplitude du mouvement de la prostate à travers une analyse rétrospective de 32 patients et d'évaluer son impacte dans la dosimétrie des traitements de la prostate avec et sans localisation US. L'analyse rétrospective a montré que la moyenne  écart-type des mouvements de la prostate dans les directions AP, SI et DG est de -3.3  7.9 mm, -1.1  6.4 mm et -0.2  5.6 mm, respectivement. La plus grande rotation survient autour de l'axe latérale, avec une moyenne  écart-type de -0.9  4.6, s'échelonnant entre -6.7 et 8.0. Pour estimer l'impacte dosimétrique du mouvement rigide de la prostate, la dose a été calculée en utilisant la méthode XVMC, qui prend en considération la géométrie du patient, les hétérogénéités et les corrections pour le mouvement. Une déviation moyenne de la D95% de jusqu'à -11.9% a été observe pour le PTV, -5.1% pour le CTV et -4.2% pour le GTV. Le V95% du PTV a été réduit par un facteur de -22.2% lorsque la translation quotidienne de la prostate était présente mais aucune correction n'a été appliquée. La dégradation de la dose à la cible a pu être corrige presque complètement en appliquant une correction du mouvement de translation, cependant lorsque la rotation a été prise en compte, le recouvrement de la dose a été moins adéquat. L'effet des prothèses m

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are different aspects of a single condition, venous thrombo-embolic disease (VTE), a major cause of morbidity and mortality in the western world. Rapid diagnosis is critical, as timely medical intervention can have a substantial beneficial effect on the mortality rate. Irrespective of its presentation, VTE is a difficult disease to diagnose. Pathologies unrelated to VTE can give rise to a clinical presentation similar to DVT or PE, resulting in a false positive diagnosis. This raises the risk of a patient being treated inappropriately. Therefore, there is a need for an agent that has high specificity and sensitivity for the detection of active blood clots, which are amenable to treatment by anticoagulant and/or thrombolytic therapy. This work describes the pre-clinical efficacy studies performed on one such agent, 99mTc-NC100668. 99mTc-NC100668 is a substrate for factor XIIIa and as a potential physiological, rather than anatomical, marker of VTE it is hoped it will not give rise to the false negative and positive diagnoses that are inherent in the currently available diagnostic techniques, such as the ventilation perfusion (V/Q) scan, multidetector computer tomography or ultrasound. It is reported in this work that 99mTc-NC100668 uptake and retention in blood clot was rapid and maintained over at least a 4 hour period in a rat model of DVT. Anticoagulant and thrombolytic therapies commonly used to treat thrombosis did not seriously impair the ability of 99mTc-NC100668 to detect thrombi. No significant tissue retention, which could interfere with the ability to image thrombi in vivo, was observed. Biodistribution and plasma clot uptake studies showed that 99mTc complex of gly-NC100194, the major metabolite of 99mTc-NC100668, would be unlikely to affect adversely the clinical utility of the test substance. The in vitro uptake of 99mTc-NC100668 into forming plasma clots indicated that retention into human blood clots would be comparable with the observations made in the rat preclinical models. The uptake of 99mTc-NC100668 in vitro and in vivo was much greater than could be accounted for by physical entrapment into the forming blood clots. The reduced uptake of a biologically inactive analogue of 99mTc-NC100668 both in vitro and in vivo indicated that the blood clot uptake and retention of 99mTc-NC100668 was mediated by factor XIIIa. In conclusion, 99mTc-NC100668 might be useful in the detection of thrombo embolism.

Thesis (MAppSc (MedRad))--University of South Australia, 1999

Thesis (M.H.A.)--University of Michigan, 1957.

Thèse (Ph.D.)--Université de Sherbrooke (Canada), 2008. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thèse (Ph.D.)--Université de Sherbrooke (Canada), 2007. / Titre de l'écran-titre (visionné le 1 février 2007). In ProQuest dissertations and theses. Publié aussi en version papier.

Thesis (M.H.A.)--University of Michigan, 1957.