REGULARIZATION OF PHASE-CONTRAST MRI VELOCITY MEASUREMENTS: INITIAL IN VIVO EXPERIENCE IN A CANINE ANEURYSM MODEL

摘要

According to the US National Institute of Neurological Disorders and Stroke, incidence of reported intracranial aneurysm (IA) rupture is about 0.001%. In other words, there are thus about 27,000 people who may suffer stroke from ruptured cerebral aneurysms each year. The origin and natural history of IAs are closely associated with disturbed hemodynamics though exact mechanisms are unknown. [1, 2] Consequently, blood flow parameters measured from phase-contrast magnetic resonance imaging (PC-MRI) [3, 4] may provide insight not only into factors relevant to the development and progression of IAs but also into their short and long term responses to therapeutic interventions (e.g. coil embolization and stent deployment). Since individual protons in complex and disturbed aneurismal flow have incoherent velocities (at the sub-grid level) cannot be resolved by one "averaged" velocity measurement from a relatively large resolution cell (at 1-mm scale), such measurement errors and potential artifacts can adversely affect accuracy of PC-MRI results. In this study, we introduced a post-processing technique for improving the accuracy of PC-MRI velocity fields and corresponding streamlines. More specifically, we implemented an iterative algorithm to enforce the incompressibility constraint, from fluid dynamics, to regularize PC-MRI measured velocity fields. We applied this algorithm to improve PC-MRI flow measurements obtained in an in vivo experimental aneurysm model [5].