Comparison of in vivo carotid 3.0-T magnetic resonance to B-mode ultrasound imaging and histology in a porcine model.

OBJECTIVES We compared in vivo 3.0-T magnetic resonance (MR) images of the carotid artery wall in piglets to intima-media thickness measurements of similar carotid segments by B-mode ultrasound (US) and histology to define the corresponding anatomical tissue characteristics and accuracy of carotid MR images. BACKGROUND Carotid MR is increasingly used for the assessment of cardiovascular risk and cardiovascular drug efficacy. Therefore, determining the anatomical correlate and accuracy of this modality is of major importance. METHODS In vivo 3.0-T MR and B-mode US scans of the left and right common carotid arteries were performed in 5 piglets (75 to 80 kg). The T(1)-weighted MR images were acquired with a noninterpolated pixel size of 0.25 x 0.25 mm for mean wall area (MWA) and mean wall thickness measurements. The B-mode US measured common carotid intima-media thickness and common carotid diameter. We calculated US MWA using common carotid intima-media thickness and carotid diameter. In histology, the intima and media tissue area was defined as histology MWA. RESULTS Histology MWA was 4.69 (standard deviation [SD]: 0.95) mm(2), MR MWA was 4.57 (SD: 0.41) mm(2), and US MWA was 4.90 (SD: 0.50) mm(2). The mean difference was 0.12 (SD: 1.11) mm(2) for MR and -0.21 (SD: 1.01) mm(2) for US when compared with histology. Bland-Altman analysis showed no systematic biases between MR, US, or histology. CONCLUSIONS Absolute values for carotid artery histology, MR, and US measurements are in good agreement, indicating that both 3.0-T MR and B-mode US measurements can visualize the intima and media. Accuracy of 3.0-T MR is comparable to B-mode US. The present findings imply that carotid MR might be a novel asset in cardiovascular disease risk stratification and a valuable surrogate marker in cardiovascular prevention trials.