The Practical Study Of USPIO Enhanced MR Black-blood Sequences In Detecting Atherosclerotic Plaques Of Rabbits

Background: Atherosclerosis, a chronic inflammatory vascular disease, is a leading cause of mortality and morbidity worldwide. With multiple sequences and parameters, MRI is emerging as the most useful tool to assess atherosclerosis in imaging area. Now, the rapid progress of nanoscience and the application of nanotechnology are changing the foundations of diagnosis and treatment of this disease. Combined with nanotechnology, targeted MRI is an exiting technique ,which can permit the detection of specific substances commonly found in vulnerable plaques , for example ,macrophages, MMPs, oxidized LDL, extracellular matrix et al. USPIO is a new nano's MRI contrast agent, which can be phagocytosed by intraplaque macrophages. The accumulation of these iron oxides in macrophages makes focal signal intensity decrease in atherosclerotic plaques. In this experiment, we use MR black-blood pulse sequences with USPIO enhancement to assess atherosclerosis on rabbits' model.Objective:1.To select best coil for assessing rabbits' abdominal aorta from our present.2.To establish atherosclerotic rabbit models within abdominal aorta.3.To detect unstable atherosclerotic plaque of atherosclerotic rabbit models by MR black-blood pulse sequences with contrast agent USPIO.Methods: Thirty New Zealand male rabbits were divided randomly into three groups: Practice group (A group, twenty), control group (B group, five) and coil group(C group, five). Atherosclerosis was induced in A group with aortic balloon endothelial injury followed by a high cholesterol diet for fourteen weeks; Control group rabbits were fed basic food without aortic balloon endothelial injury, water free. C group rabbits was used to select best coil for assessing rabbits' abdominal aorta. After fourteen weeks, the rabbits were examined by MRI and USPIO enhanced MRI for five days on 1.5 T MR scanner (Philips Eclipse). Sequences included T1-weighted turbo field echo, T2-weighted PD-weighted fast spin-echo and T2*-weighted 3D TOF fast field echo. To detect the change of the SNR on vessel wall, we draw the curve chart follow the change of SNR for five days and find the optimal time of reinforcement. After examination, rabbits were killed and abdominal aortas were separated for pathological study, including HE stain and Prussian blue stain. The MR images of atherosclerotic vessel walls were analyzed and compared with corresponding histology.Results: We concluded that knee joint coil is the best one for assessing rabbits' abdominal aorta. Many plaques can be seen in abdominal aortas of practice group rabbits with fibrous tissue, lipid and necrotic core, calcium, so there is a good similarity between rabbit and human. The different components of the atherosclerotic lesions were demonstrated different MR signals, the lipid rich core appears light on T1WI,PDWI and T2*WI,but dark on T2WI and USPIO enhanced T2*WI image.Conclusion:1.Atherosclerotic plaque model can be successfully established by balloon endothelial injury followed by a high cholesterol diet in rabbit abdominal aorta.2.USPIO can be phagocytosed by macrophages within rabbit's abdominal aortic plaques and lead to MR signal intensity change.3.USPIO enhanced MR black-blood pulse sequences have a definite value for assessing rabbit's plaques within abdominal aortic.