Carotid MRI Detection of Intraplaque Hemorrhage at 3T and 1.5T

Background and purpose: Carotid intraplaque hemorrhage leads to plaque progression and ischemic events. Detection can be accomplished with 3T T1w sequences, but may be limited by false-positive lipid/necrosis. The purpose of this study was threefold: (1) to determine if magnetization-prepared rapid acquisition with gradient-echo (MPRAGE) detects intraplaque hemorrhage versus lipid/necrosis; (2) if 3T MPRAGE image quality is retained at 1.5T; and (3) to determine observer agreement.

Methods: MPRAGE positive areas were compared to hemorrhage and lipid/necrosis areas from 100 carotid endarterectomy slides in 12 subjects using multivariable linear regression. Image quality was determined between 3T and 1.5T in 716 carotid arteries using t-tests and multivariable linear regression. Kappa analysis was used to determine agreement.

Results: Intraplaque hemorrhage, not lipid/necrosis, was a significant predictor of MPRAGE positive area before and after adjusting for confounders (slope = .52 vs. .51, P < .001). Image quality at 3T was slightly lower than 1.5T (mean 3.87 vs. 4.34, P < .0001). 3T image quality remained slightly decreased before and after adjusting for confounders (slope = -.46 vs. -.41, P < .001). Kappa values for inter-/intraobserver agreement were .807/.919 at 3T and .803/.871 at 1.5T.

Conclusions: Carotid MPRAGE detects intraplaque hemorrhage, not lipid/necrosis. 3T image quality was retained at 1.5T with very good observer agreement.