Background--Noninvasive imaging can detect early atherosclerotic disease. Magnetic resonance imaging (MRI), because of its excellent spatial resolution, is already established as a tool for plaque characterization. Sixteen-slice, multidetector-row computed tomography (MDCT) was recently introduced into the field of cardiac imaging, with promising results for noninvasive angiography. We compared the capabilities of MDCT and MRI for the assessment of noncalcified, atherosclerotic plaques.

Methods and Results--Six atherosclerotic rabbits underwent in vivo imaging by MDCT and 1.5-T MRI. MDCT parameters were 120 kV, 120 mA/s, collimation 12x0.75, and spatial resolution 0.6x0.6 mm. MRI parameters were as follows: for proton density, repetition time/echo time (TR/TE) 2300/5.6; for T2, TR/TE 2300/62; and for T1, TR/TE 800/5.6; slice thickness was 3 mm and spatial resolution, 0.3x0.3 mm. Blinded analysis of 3-mm axial reconstructions from MDCT and the carefully matched MRI images (182 sections) showed excellent agreement between both modalities. MDCT yielded a slightly larger lumen area, anteroposterior diameters, and lateral diameters, with no significant differences in total vessel area. The sensitivity and specificity, respectively, to detect noncalcified, atherosclerotic plaques were 89% and 77% for MDCT and 97% and 94% for MRI. Fibrous-rich and lipid-rich plaque could not be differentiated visually, although they showed different attenuation properties (116±27 vs 51±25 Hounsfield units, P<0.01).

Conclusions--Both techniques allow reliable detection of noncalcified, atherosclerotic plaques and accurate assessment of vessel areas and diameters. MDCT offers the additive value of a very short image acquisition time when compared with MRI. The subtle measurement differences found between modalities may be due to the better spatial resolution of MRI, which probably explains its superiority for tissue characterization.