Direct Imaging and Quantification of Carotid Plaque Calcification

Carotid plaque calcification normally appears as a signal void with clinical MR sequences. Here, we describe the use of an adiabatic inversion recovery prepared two-dimensional ultrashort echo time sequence to image and characterize carotid plaque calcification using a clinical 3-T scanner. T-1, T-2(star), and free water content were measured for seven carotid samples, and the results were compared with micro-CT imaging. Conventional gradient echo and fast spin echo images were also acquired for comparison. Correlations between T-1, T-2(star), free water concentration, and mineral density were performed. There was a close correspondence between inversion recovery prepared two-dimensional ultrashort echo time morphologic and micro-CT appearances. Carotid plaque calcification varied significantly from sample to sample, with T(1)s ranging from 94 +/- 19 to 328 +/- 21 msec, T(2)(star)s ranging from 0.31 +/- 0.12 to 2.15 +/- 0.25 msec, and free water concentration ranging from 5.7 +/- 2.3% to 16.8 +/- 3.4%. There was a significant positive correlation between T-1 (R = 0.709; P < 0.074), T-2(star) (R = 0.816; P < 0.025), and free water concentration, a negative correlation between T-1 (R = 0.773; P < 0.042), T-2(star) (R = 0.948; P < 0.001) and CT measured mineral density, and a negative correlation between free water concentration (R = 0.936; P < 0.002) and mineral density. Magn Reson Med 65:1013-1020, 2011. (C) 2010 Wiley-Liss, Inc.