Distinguishing type I and type II hemorrhage by gradient echo based MR sequence in carotid atherosclerotic plaques

Abstract

Methods Five ex vivo carotid endarterectomy (CEA) specimens were imaged on a 3T MR scanner (Philips Achieva) after formalin fixation. Firstly, a GRE sequence was optimized with different echo time (from 4.1ms to 9.1ms) to obtain the greatest contrast between type I and type II hemorrhages which were verified by histology. Secondly, four contrast MR weightings including T1 weighted (T1W), T2 weighted (T2W), Proton density weighted (PDW) and GRE with optimized parameters (Table 1) were acquired. Histology specimens were stained using hematoxylin and eosin (H&E) and Mallory’s trichrome at the location according to MRI slices. The histologist, blinded to the MR images, outlined IPH regions. Morphological features of lumen, vessel wall, and the relative position of external carotid and internal carotid on histology were used for registration. The regions on MR images corresponding to type I and type II hemorrhage on histological slides were mapped by a trained reviewer. The CNR was compared between these regions.