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

Raphaël Duivenvoorden, MD^_*, Eric de Groot, MD, PhD^_*, Hamid Afzali, MD^_*, Ed T. VanBavel, PhD, Onno J. de Boer, PhD, Johan S. Laméris, MD, PhD, Zahi A. Fayad, PhD^||, Erik S.G. Stroes, MD, PhD^_*, John J.P. Kastelein, MD, PhD^_*, Aart J. Nederveen, PhD^,_*

^_* Department of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
Department of Biomedical Engineering and Physics, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
^|| Translational and Molecular Imaging Institute, Mount Sinai School of Medicine, New York, New York

^_* Reprint requests and correspondence: Dr. Aart J. Nederveen, Radiology, Academic Medical Center, Z0-120, Meibergdreef 9, 1105 AZ Amsterdam, the Netherlands (Email: a.j.nederveen{at}amc.uva.nl).

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 T₁-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) 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.

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.

Key Words: atherosclerosis • intima-media thickness • carotid artery • magnetic resonance • ultrasound

Abbreviations and Acronyms   CCIMT = common carotid intima-media thickness   ECG = electrocardiography   IMT = intima-media thickness   MR = magnetic resonance   MWA = mean wall area   MWT = mean wall thickness   US = ultrasound