Gradient echo MRI characterization of development of atherosclerosis in the abdominal aorta in Watanabe Heritable Hyperlipidemic rabbits

• Published in: Cardiovascular and interventional radiology 2006-08, Vol.29 (4), p.605-612
• Main Authors: Wang, Yi-Xiang J, Kuribayashi, Hideto, Wågberg, Maria, Holmes, Andrew P, Tessier, Jean J, Waterton, John C
• Format: Article
• Language: English
• Subjects: Aging; Aneurysms; Animals; AORTA; ARTERIOSCLEROSIS; Atherosclerosis; Atherosclerosis - genetics; Atherosclerosis - pathology; Atherosclerosis - physiopathology; BLOOD; CHEMICAL SHIFT; Disease Models, Animal; Echo-Planar Imaging - methods; Female; HISTOLOGY; Hyperlipidemias - genetics; Hyperlipidemias - pathology; Hyperlipidemias - physiopathology; KIDNEYS; NMR IMAGING; RABBITS; RADIOLOGY AND NUCLEAR MEDICINE; THICKNESS
• ISSN: 0174-1551; 1432-086X
• DOI: 10.1007/s00270-005-0073-5

The Watanabe Heritable Hyperlipidemic (WHHL) rabbit provides an important model of spontaneous atherosclerosis. With a strain of WHHL rabbits which do not develop abdominal aorta lumen stenosis even with advanced atherosclerosis, we studied the MRI-histology correlation, and the natural progression of atherosclerosis in the abdominal aorta. In addition, intra-reader segmentation repeatability and scan-rescan reproducibility were assessed. Two batches of female WHHL rabbits were used. The first batch of 6 rabbits was scanned at 20 weeks old. A second batch of 17 rabbits was scanned at 50 weeks old and then randomly divided into two subgroups: 8 were killed for histologic investigation; 9 were kept alive for follow-up, with repeat scanning a week later to assess scan-rescan reproducibility, and again at 73 weeks old to assess disease progression. MR images were acquired at 4.7 T using a chemical shift selective fat suppression gradient echo with a saturation band suppressing blood signal within the aortic lumen. Five slices per animal were acquired, centered around the renal artery region of the abdominal aorta, with in-plane resolution of 0.195 mm and slice thickness of 3 mm. The coefficient of variation for intra-reader reproducibility for aortic wall thickness measurements was 2.5% for repeat segmentations of the same scans on the same day, but segmentations of these same scans made 8 months later showed a systematic change, suggesting that intra-reader bias as well as increased variability could compromise assessments made over time. Comparative analyses were therefore performed in one postprocessing session. The coefficient of variation for scan-rescan reproducibility for aortic wall thickness was 5.5% for nine pairs of scans acquired a week apart and segmented on the same day. Good MRI-histology correlation was obtained. The MRI-measured mean aortic wall thickness of animals at 20 weeks of age was 76% that of animals at 50 weeks of age (p < 0.001). There was a small increase in aortic wall thickness between 50 and 73 weeks of age, but this was not significant (p > 0.05). The corresponding differences in lumen cross-sectional areas at 20, 50, and 73 weeks of age were not significant. These results were consistent with in-house historical histology data on this strain of rabbits. High-resolution gradient echo MRI can follow disease progression in the WHHL rabbit spontaneous atherosclerosis disease model.