Comparison of In Vivo Carotid 3.0-T Magnetic Resonance to B-Mode Ultrasound Imaging and Histology in a Porcine Model

ObjectivesWe 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.BackgroundCarotid 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.MethodsIn 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 T1-weighted MR images were acquired with a noninterpolated pixel size of 0.25 × 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.ResultsHistology MWA was 4.69 (standard deviation [SD]: 0.95) mm2, MR MWA was 4.57 (SD: 0.41) mm2, and US MWA was 4.90 (SD: 0.50) mm2. The mean difference was 0.12 (SD: 1.11) mm2 for MR and –0.21 (SD: 1.01) mm2 for US when compared with histology. Bland-Altman analysis showed no systematic biases between MR, US, or histology.ConclusionsAbsolute 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.