兔动脉粥样硬化斑块：USPIO增强MR与Gd-DTPA增强MR对比实验研究

Comparative Study of USPIO Enhanced MR Imaging and Gd DTPA Enhanced MR Imaging in Atherosclerotic Plaques of Rabbits

目的在MR连续观察下,采用自制超小超顺磁性氧化铁(ultrasmall superparamagnetic iron oxide,USPIO),与钆喷酸葡胺(Gd-DTPA)对比,分别对动脉粥样硬化(AS)兔行增强MR检查,旨在探讨USPIO增强MR对AS兔的价值。材料与方法35只雄性新西兰大白兔随机分为两组,25只给予高脂饮食诱导动脉粥样硬化,10只给予正常饮食作为对照组。所有扫描均在1.5 T磁共振扫描仪上进行,采用Cardiac线圈。扫描序列包括:T1WISE,T1WI SE脂肪抑制,T2WI FSE,T2*WI GRE。所有动物于喂养10周时测血清总胆固醇量,并进行平扫及USPIO增强24 h扫描,1周后行Gd-DTPA增强扫描,完成Gd-DTPA增强扫描当天处死不同喂养阶段模型兔及同期对照组正常兔,整个过程每2周重复一次。USPIO使用剂量为0.05 mmolFe/kg体重,Gd-DTPA使用剂量为0.25 mmol/kg体重。MR所见与病理相对照。结果喂养10周时模型兔血清总胆固醇值明显高于正常组(P<0.05),且所有模型兔大体标本均发生肉眼可见动脉粥样硬化样改变,除5只模型兔喂养中途死亡,其余兔均完成全程扫描。病理证实斑块内巨噬细胞吞噬USPIO。USPIO增强MR较Gd-DTPA增强能更好识别斑块内各种成分。结论US-PIO增强MR对识别斑块成分具有独特价值,并能反映斑块内炎性浸润,因此对判断斑块易损性优于Gd-DTPA增强MR。

Objective To explore the value of USPIO enhanced MR imaging of atherosclerotic plaques in rabbits, and compared with Gd DTPA enhaened MR imaging. Materials and Methods 35 male New Zealand white rabbits were randomly assigned to two groups. 25 rabbits were induced by atherogenic diet to set up the model. 10 rabbits with the normal diet were served as the control group. All MR were performed on a high-resolution 1.5T MR scanner with the cardiac coil. Routine sequences included T1-weighted spin-echo, T1-weighted spin-echo with fat saturation, T2-weighted fast spin-echo, T2 ＊ -weighted gradient-echo. 10 weeks later, the blood of all the rabbits were gathered to test the content of total cholesterol, then, they were imaged prior to and 24 hours after administration of USPIO. A week delay, to ensure the excretion of USPIO, all the animals performed Gd DTPA-enhaneed MR imaging, then the rabbits were killed in different raising periods, and this was repeated every 2 weeks. USPIO was injected intravenously at a dose ofO. 05mmol Fe/kg body weight. Gd DTPA was injected intravenously at a dose of 0.25mmol/kg body weight. MR findings were correlated with histopathologic findings. Results The total cholesterol in model group was obviously higher then that in the normal group （P 〈 0.05）. Rabbits induced by atherogenic diet were all developed atherosclerotic lesion on gross, all the rabbits were finished the whole study except for 5 AS rabbits, which were died a natural death, and the lesions monitored by MR were well correlated with histopathologic findings. The analysis of pathology proved that the USPIO particles were in the macrophages of the plaque.USPIO-enhaneed MR imaging characterized the composition of atheroselerotic plaques better than that by Gd DTPA-enhanced MR imaging. Conclusion USPIO-enhanced MR imaging has unique value in characterizing the composition of atherosclerotic plaques, it also can be used to evaluate the inflammatory burden in the plaque, it is superior to Gd DTPAenhanced MR imaging to depicting the vulnerable of atherosclerotie plaque.