Clarke Sharon E, Beletsky Vadim, Hammond Robert R, Hegele Robert A, Rutt Brian K
Imaging Research Laboratories, Robarts Research Institute, PO Box 5015, London, Ontario, Canada.
Stroke. 2006 Jan;37(1):93-7. doi: 10.1161/01.STR.0000196985.38701.0c. Epub 2005 Dec 8.
MRI may be used for noninvasive assessment of atherosclerotic lesions; however, MRI evaluation of plaque composition requires validation against an accepted reference standard, such as the American Heart Association (AHA) lesion grade, defined by histopathological examination.
Forty-eight carotid endarterectomy specimen cross-sections had AHA lesion grade determined histopathologically and were concurrently imaged using combinations of 8 MRI contrast weightings in vitro. A maximum likelihood classification algorithm generated MRI "maps" of plaque components, and an AHA lesion grade was assigned correspondingly. Additional analyses compared classification accuracy obtained with a commonly used set of magnetic resonance contrast weightings [proton density (PDw), T1 (T1w), and partial T2 (T2w)] to accuracy obtained with the combination of PDw, T1w, and diffusion-weighted (Dw) contrast.
For the 8-contrast combination, the sensitivities for fibrous tissue, necrotic core, calcification, and hemorrhage detection were 83%, 67%, 86%, and 77%, respectively. The corresponding specificities were 81%, 78%, 99%, and 97%. Good agreement (79%) between magnetic resonance and histopathology for AHA classification was achieved. For the PDw, T1w, and Dw combination, the overall classification accuracy was insignificantly different at 78%, whereas the overall classification accuracy using PDw, T1w, and partial T2w contrast weightings was significantly lower at 67%.
This study provides proof-of-principle that the composition of atherosclerotic plaques determined by automated classification of high-resolution ex vivo MRI accurately reflects lesion composition defined by histopathological examination.
磁共振成像（MRI）可用于对动脉粥样硬化病变进行无创评估；然而，MRI对斑块成分的评估需要对照公认的参考标准进行验证，如通过组织病理学检查定义的美国心脏协会（AHA）病变分级。
48个颈动脉内膜切除术标本的横截面通过组织病理学确定AHA病变分级，并同时在体外使用8种MRI对比加权组合进行成像。最大似然分类算法生成斑块成分的MRI“图谱”，并相应地指定AHA病变分级。额外的分析将使用一组常用的磁共振对比加权[质子密度（PDw）、T1（T1w）和部分T2（T2w）]获得的分类准确性与使用PDw、T1w和扩散加权（Dw）对比组合获得的准确性进行比较。
对于8种对比组合，纤维组织、坏死核心、钙化和出血检测的敏感性分别为83%、67%、86%和77%。相应的特异性分别为81%、78%、99%和97%。在AHA分类方面，磁共振成像与组织病理学之间达成了良好的一致性（79%）。对于PDw、T1w和Dw组合，总体分类准确性为78%，差异不显著，而使用PDw、T1w和部分T2w对比加权的总体分类准确性显著较低，为67%。
本研究提供了原理证明，即通过高分辨率离体MRI自动分类确定的动脉粥样硬化斑块成分准确反映了由组织病理学检查定义的病变成分。
