Abstract TP241: Correlation of Mri Cerebral Perfusion Parameters and Carotid Plaque Characteristics

Abstract

Purpose: Recent evidence suggests that MRI-detected intraplaque hemorrhage (IPH) improves stroke prediction in all carotid stenosis categories, placing the role of stenosis and impaired perfusion in question. The goal of this study was to determine if carotid stenosis or IPH are associated with baseline perfusion impairment measured by dynamic susceptibility contrast (DSC) and cellular diffusion and perfusion measured by intravoxel incoherent motion (IVIM). Method and Materials: After IRB approval and informed consent, we recruited 25 patients with >=50% stenosis in at least one carotid. Carotid MRI and brain IVIM and DSC were performed at 3T. IVIM was acquired with b-values of 20, 40, 50, 100, 250, 500, and 2000. Post-processing was performed (IVIM with Osirix, and DSC with Olea Sphere). Bilateral regions of interest were drawn in the centrum semiovale with the following measurements obtained for IVIM: percent perfusion fraction (f), tissue diffusion (D), pseudodiffusion (D*) and blood flow related parameter (fD*). DSC parameters included cerebral blood flow (CBF), blood volume (corrected CBV), mean transit time (MTT), and time to peak (TTP). Generalized estimating equations (GEE) and multivariable linear regression was performed accounting for two carotid arteries per patient, to determine the association of each IVIM and DSC perfusion parameter with carotid imaging factors including stenosis, occlusion, near-occlusion, and IPH. Results: Near-occlusion was rare (2/50 carotids) but was the only factor associated with DSC parameters (CBF: coefficient=-9.7, p=0.016, corrected CBV: coefficient=-0.36,p=0.042, MTT: coefficient=1.1,p=0.010, and TTP: coefficient=2.2,p=0.008). Near occlusion was also the only factor associated with the IVIM parameters f (coefficient=1.7, p=0.057) and fD* (coefficient=44, p=0.045). Carotid IPH was the only factor associated with D (coefficient=45, p=0.002). None of the factors were significantly associated with D*. Conclusion: These results suggest that carotid stenosis does not result in decreased baseline cerebral perfusion except in the rare setting of near-occlusion. While these patients may benefit from flow restoration, most patients may primarily benefit from embolic protection.