Evaluation of Dynamic Contrast Enhanced MRI in the Temporomandibular Joint in Children With Juvenile Idiopathic Arthritis
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Under the hypothesis that an inflammation in the temporomandibular joint (TMJ) is accompanied with increased vascularity [1,2], measures of the blood micro circulation can be indicative of inflammatory processes in Juvenile Idiopathic Arthritis (JIA) [?]. Dynamic Contrast Enhanced (DCE) Magnetic Resonance Imaging (MRI) can be used to measure features of the vascularity and thus holds the potential to be a diagnostic tool also in JIA. DCE MRI captures biological processes in time, and an implementation using high temporal resolution (4s), is in the current thesis being evaluated for the first time in the TMJ, in children with JIA. Motion correction schemes are also applied to the TMJ for the first time. By systematically down sampling the data, and by application of motion correction schemes, it is found that high temporal resolution (at least 12s) data and an elastic motion correction scheme should be applied for best possible data quality. The elastic motion correction scheme allows a more data from moving participants to be included. Both direct semi quantitative measures and advanced tracer kinetic modelling based on the Gamma Capillary Transit Time (GCTT) model are used to generate parameters describing the physiology of the TMJ. The ability of these parameters to categorize participants into groups of affected and non-affected participants is considered by comparing scores obtained from ultrasound examinations and structural MR images to the estimated parameters. It is found that age, gender and acquisition site in general do not systematically affect the estimated parameters. Consequently, multi-centre studies on a range of JIA patients are possible. It is also found that, at present, even though advanced tracer kinetic parameters may be better suited for diagnostic purposes than more direct semi quantitative measures, it is not possible to distinguish groups of affected and non-affected participants as defined by clinical ultrasound and structural images by evaluating the distributions of parameters within these groups. To potentially improve the diagnostic accuracy of the DCE-MRI approach, parameters should be estimated with a greater level of precision, in the hope that present data variability is due to methodological shortcomings and not inherent variability caused by biological differences between the participants. DCE-MRI parameters could also be monitored as a function of time, so that participants can be followed on an individual basis.
PublisherThe University of Bergen
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