Proefschrift Universiteit Utrecht. / Ook verschenen in gedrukte vorm.

Proefschrift Universiteit Maastricht. / Met bibliogr., lit. opg. - Met een samenvatting in het Duits.

Proefschrift Universiteit Maastricht. / Met bibliogr., lit. opg. - Met samenvatting in het Nederlands.

Proefschrift Universiteit Maastricht. / Met lit. opg. - Met samenvatting in het Nederlands.

Proefschrift Universiteit Maastricht. / Met bibliogr., lit. opg. - Met samenvatting in het Nederlands.

Proefschrift Universiteit Maastricht. / Met lit. opg. - Met samenvatting in het Nederlands.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Cardiac Magnetic Resonance Imaging (CMRI) is an important and valuable tool in the routine management of patients with cardiovascular disease. Contrast enhanced CMRI allows detection of ischemic and scarred myocardium, including rare infiltrative processes that cause cardiomyopathies. Amyloidosis comprises a group of diseases that are characterized by the extracellular deposition of insoluble fibrillar proteins in organs. The deposition of amyloid material in the heart leads to presentations of congestive heart failure mainly of the restrictive infiltrative pattern. There may be also conduction abnormalities. Dilated cardiomyopathy is a form of cardiomyopathy that is characterized by abnormal dilatation of the heart and subsequent heart failure. One of the characteristics of the cardiomyopathies and amyloidosis is the diffuse interstitial or replacement myocardial fibrosis. Myocardial fibrosis leads to impaired cardiac diastolic and systolic function and can lead to increased cardiovascular morbidity and mortality. Cardiac Magnetic Resonance Imaging (CMRI) with contrast can be used to characterize the extent of myocardial fibrosis through T1 mapping and as such it can be used as a prognostic indicator in amyloidosis and dilated cardiomyopathy. / 2031-01-02

The human masseter muscle is a structurally complex jaw elevator with the capability of generating high, multidirectional forces. The invasiveness of current anatomical and physiological methods has, however, limited both the number and scope of studies of human masseter muscle structure and function. Therefore the aim of this work was to apply in vivo magnetic resonance (MR) techniques to elucidate the three-dimensional internal architecture of the human masseter muscle and its metabolic response to exercise in order to gain a better understanding of the jaw muscles in health and disease. In the first of these experiments, five adult subjects were selected and examined using cephalometric radiography, magnetic resonance imaging (MRI) and three-dimensional rotational and reconstructive computer graphics to describe the organization of tendon planes within the masseter muscle. Planar quadrilaterals representing putative tendon planes were fitted to the surfaces of the three-dimensional muscle reconstructions, and these were related to the mid-sagittal plane in the coronal and axial views. To confirm whether putative planes disclosed by MRI represented true anatomic entities, a fresh human cadaver head was imaged by MRI and then cryosectioned at millimetre intervals. Planar sections through the reconstructed muscle generated from the cadaver cryosections were correlated with the actual MR images in the same planes. Tendon plane angulation appeared to be related to ramal length and lower face height measured cephalometrically. In the axial view, the tendon planes appeared roughly to follow the angulations of the zygomatic arch and the lateral face of the mandibular ramus. Our results suggest that the angulation of tendon planes, and possibly pennation angles are different depending on the viewing angle, and infer that muscle fibres inserting on either side of a central tendon may need to develop different tensile forces if translation is to occur directly along the tendon axis. In the second, 31P magnetic resonance spectroscopy (MRS) was utilized to examine the masseter muscles of six adult males at rest and performing stereotyped isometric clenching exercises. 31P MR spectra were acquired from three locations within the muscle using a 2cm by 3cm, single-turn, copper receiver coil. The spectra were quantified on the basis of relative peak area and position. The organic phosphate (Pi) to creatine phosphate (PCr) ratio (Pi/PCr), which has been shown to be proportional to free ADP concentration and hence, the metabolic activity, as well as the normalized Pi concentration ([Pi]) and pH, were calculated for each site and exercise. The mean resting Pi/PCr ratio and [Pi] were greater for the deep part of the muscle than for the superficial and intermediate parts. These differences were significant to p<0.01. The mean pH however, was similar in all parts of the muscle at rest. During exercise, a significant increase in mean Pi/PCr was found in the superficial and intermediate parts of the muscle. Both these differences were significant to p<0.05. An accompanying decrease in mean pH was observed in all parts of the muscle during exercise. In the superficial part of the muscle, this decrease was significant to the p<0.05 level, and in the deep part, the decrease was significant to the p<0.001 level. No significant differences were found for these parameters between left and right molar clenching. These results suggest that metabolic activity may be monitored in the masseter muscle using 31P MR spectroscopy and that task-dependent and regional variations in metabolic activity may be demonstrated both at rest and during exercise. They are promising enough to encourage future studies of muscle metabolism in subjects with jaw muscle disorders. These experiments demonstrate the novel application of magnetic resonance techniques for studying craniomandibular morphology and function non-invasively. Collectively, they reveal the anatomical and functional heterogeneity which exist in the human masseter muscle. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Medicine Johannesburg, 2018. / The knee is indispensable in everyday life and injuries to it can be debilitating with significant loss of earnings incurred. Clinical diagnosis may not always be made with certainty and Magnetic Resonance Imaging (MRI) helps further elucidate intra-articular injuries. MRI reporting has its shortcomings and may provide spurious results according to the interpretor’s level of experience. This study aims to test the diagnostic reliability of MRI done in a teaching hospital for the evaluation of anterior cruciate ligament and meniscal injuries using arthroscopy as the baseline for comparison. Due to the long waiting times to have surgery we also determined if there was a change in the reliability of an MRI result as time elapsed. A retrospective review of records of patients who had knee arthroscopies at Chris Hani Baragwanath Academic Hospital (Johannesburg, South Africa) from May 2009 to May 2015 was done. Adults (16 − 60 years) with one major episode of trauma to the knee and had MRI done prior to surgery at the above institution were included. Arthroscopy was performed by 2 senior surgeons or by residents under their direct supervision. Arthroscopic findings of anterior cruciate ligament (ACL) and medial (MM) or lateral meniscal (LM) injuries were compared to MRI findings. Data was analysed by STATA version 13.1 to determine injury demographics, sensitivity, specificity and diagnostic accuracy of MRI. The effect of time interval from MRI to surgery on the diagnostic accuracy was determined. A total of 72 patients (74 knees) qualified for review. The median age was 35 years (IQR 26 − 43) with a significant difference between males and females (28 vs 41 years, p = 0.0019). Leading causes of injury were traffic accidents (32.4%), falls (27.0%) and sports injuries (17.6%). Median interval from MRI to surgery was 71.5 days (IQR 29 − 143). The sensitivity of MRI for ACL, MM and LM injuries was (63.6%, 58.8% and 52.6%), specificity (92.7%, 86.0% and 80.0%) and diagnostic accuracy (79.7%, 79.7% and 73.0%) respectively. The patients were divided into subgroups of early (< 6 weeks), intermediate (6 − 16 weeks) and late intervention (> 16 weeks) post-MRI. There were marked differences in the diagnostic accuracy in the three groups for the ACL (70.8% vs 92.6% vs 73.9%) and LM (62.5% vs 81.5% vs 73.9%). This was unremarkable for the MM (75.0% vs 81.5% vs 82.6%). MRI findings correlate well with arthroscopic findings making it a reliable preoperative screening tool for ACL and meniscal injuries. However its diagnostic accuracy appears to change with time. It is apparent that the diagnostic accuracy is higher between 6 − 16 weeks post MRI. A bigger cohort would help determine an ideal waiting time interval without significant depreciation in diagnostic accuracy. / LG2018