Séance Séminaire

Soutenances de thèses

Hemodynamic simulations for MRI: quality control, optimization and integration to the clinical practice

This thesis aims at studying how the 4D ow MRI sequence performs. To begin with, the impact of acceleration techniques (GRAPPA, compressed sensing) on reconstructed velocity  elds is studied. The sequences are investigated in a framework combining experimental measurements of non-accelerated and accelerated sequences in a phantom and computational uid dynamics (CFD) simulations. It is shown that the highly accelerated sequence with compressed sensing is in good agreement with numerical simulation as long as appropriate corrections are applied, in particular with respect to the eddy currents. Then, the impact of a sequence parameter, namely partial echo, is investigated. On the one hand this parameter leads to a reduction of the volume of MR data acquired, which could deteriorate the reconstructed MR images. On the other hand it also mitigates commonly observed misregistration artifacts. To answer this question, a methodology coupling the simulation of the MR acquisition process with CFD and allowing to reconstruct synthetic MR images (SMRI) is used. Such a con guration is freed from experimental errors and allows to only focus on the errors intrinsic to the MRI process. Simulations are conducted with realistic constructor sequences on two types of ow. For both ows, the sequence with partial echo results in overall better results. Besides, the coupled MRI-CFD simulation appears as a tool of interest in the context of sequence design and optimization, and could be expanded to other types of MR sequences.