Wang Yi-Xiang J, Kuribayashi Hideto, Wågberg Maria, Holmes Andrew P, Tessier Jean J, Waterton John C
AstraZeneca, 21XF, Mereside, Alderley Park, Macclesfield, Cheshire, SK10 4TG, UK.
Cardiovasc Intervent Radiol. 2006 Jul-Aug;29(4):605-12. 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.
渡边遗传性高脂血症（WHHL）兔是自发性动脉粥样硬化的重要模型。我们利用一组即使患有晚期动脉粥样硬化也未出现腹主动脉管腔狭窄的WHHL兔，研究了磁共振成像（MRI）与组织学的相关性以及腹主动脉粥样硬化的自然进展情况。此外，还评估了阅片者内部分割的可重复性以及扫描 - 重扫描的再现性。
使用两批雌性WHHL兔。第一批6只兔子在20周龄时进行扫描。第二批17只兔子在50周龄时进行扫描，然后随机分为两个亚组：8只处死进行组织学研究；9只存活用于随访，一周后重复扫描以评估扫描 - 重扫描的再现性，73周龄时再次扫描以评估疾病进展。在4.7 T磁场下，采用化学位移选择性脂肪抑制梯度回波序列，通过饱和带来抑制主动脉管腔内的血液信号，获取每只动物的磁共振图像。围绕腹主动脉肾动脉区域采集5层图像，平面分辨率为0.195 mm，层厚为3 mm。
同一天对相同扫描图像进行重复分割时，阅片者内部主动脉壁厚度测量的再现性变异系数为2.5%，但8个月后对相同扫描图像进行分割时显示出系统性变化，这表明阅片者内部偏差以及变异性增加可能会影响随时间进行的评估。因此，在一个后处理环节中进行了对比分析。一周内采集并在同一天分割的9对扫描图像中，主动脉壁厚度的扫描 - 重扫描再现性变异系数为5.5%。获得了良好的MRI与组织学相关性。20周龄动物的MRI测量的平均主动脉壁厚度是50周龄动物的76%（p < 0.001）。50至73周龄之间主动脉壁厚度有小幅增加，但不显著（p > 0.05）。20、50和73周龄时管腔横截面积的相应差异不显著。这些结果与该品系兔子的内部历史组织学数据一致。
高分辨率梯度回波MRI可追踪WHHL兔自发性动脉粥样硬化疾病模型中的疾病进展。
