MR多技术扫描检测活性心肌及其影像学对比的实验研究

目的 评估各种影像学方法检测活性心肌的价值。材料与方法 建立慢性心肌缺血模型猪10头，分别于制作模型前和后1～2月进行磁共振多技术扫描及小剂量多巴酚丁胺负荷超声心动图（LDDSE）、^201TI单光子发射计算机体层显像（^201TI SPECT）、正电子发射体层显像（^18F-PET）检查，判断心肌缺血区和坏死区的大小，并与病理结果对照了解各种方法的敏感性、特异性。结果 7头动物顺利完成所有检查，负荷磁共振电影扫描见10个（8．93％）节段为梗死心肌，6个（5．36％）节段为缺血心肌；心肌灌注扫描见34个（30．35％）节段缺血，心肌活性扫描见12个（10．71％）节段坏死。LDDSE检查见8个（7．14％）节段为梗死心肌，9个（8．04％）节段为缺血心肌。SPECT检查见9个（8．04％）节段为梗死心肌。PET检查见17个（15．18％）节段为梗死心肌。TTC染色见14个（12．50％）节段为梗死区。MR电影检出的坏死节段比TTC染色显示的节段少并有统计学意义（P=0．0455，Kappa=0．8100）；MR活性扫描检出的坏死节段比TTC染色显示的坏死节段略少但无统计学意义（P=0．1573，Kappa=0．9130）。LDDSE检出的坏死节段较TTC染色显示的节段少并有统计学意义（P=0．0140，Kappa=0．7000）；PET检出的坏死节段多于磁共振活性扫描（P=0．0253，Kappa=0．8028）和MR电影扫描（P=0．0082，Kappa=0．7079）并有统计学意义；亦多于TTC染色显示的坏死节段（P=0．0833，Kappa=0．8879），但无统计学意义；SPECT检出的坏死节段比TTC染色显示的节段少并有统计学意义（P=0．0253，Kappa=0．7590）。以TTC染色结果为金标准，MRI电影、MRI活性扫描、LDDSE、SPECT、PET检出无活性心肌的敏感性、特异性分别为71．43％、100％；85．71％、100％；57．10％、100％；64．29％、100％；100％、96．94％。结论 MR多技术扫描可结合形态、功能及灌注多种方法检测活性心肌．清晰显示心肌梗死的位置、程度，并可对左窒室壁运动进行直观显示，且价格相对PET便宜；磁共振和PET、病理结果均有较高一致性。PET高估心肌坏死范围，且不能判断心肌梗死的透壁程度。SPECT和LDDSE低估心肌活性。而且亦不能显示心肌梗死的透壁程度。

An Experimental Study of Multimodality MR Imaging in Determination of Myocardial Viability Compared with SPECT, PET and Echocardiography

Objective To evaluate the diagnostic value for myocardial viability by using various imaging methods.Materials and Methods Chronic myocardial ischemia animal model in 10 pigs were established and underwent with multimodality MR imaging, 18F fluorodeoxyglucose positron emission tomography (PET),~ 201 Tl single photon emission computed tomography(SPECT) and low-dose dobutamine stress echocardiography (LDDSE) before and after 1 to 2 month modeling, respectively. The size of myocardial ischemia and necrosis were judged and compared with pathology results to assess the sensitivity and specificity of various imaging methods. Results 7 pigs were completed all examination successfully. Stress MRI detected 10 (8.93%) segments as necrosis, 6 (5.36%) segments were ischemic. Perfusion was abnormal in 34(30.35%) segments as ischemia. Delayed hyperenhancement was observed in 12(10.71%) segments as necrosis. LDDSE detected 8 (7.14%) segments as necrosis, 9(8.04%) segments as ischemic. PET showed 17(15.18%) segments of myocardial necrosis. SPECT showed 9(8.04%) segments of myocardial necrosis. Triphenyl tetrazolium chloride(TTC) determined 14(12.50%) segments of necrosis. Necrosis segments determined by PET significantly were more than that by contrast enhanced MR imaging (P=0.0253, Kappa=0.8028) and cine MRI (P=0.0082, Kappa=0.7079), it was also more than TTC (P=0.0833, Kappa=0.8879), but had no significant statistic difference. Necrosis segments determined by SPECT significantly were less than that by TTC (P=0.0253, Kappa=0.7590), which had significant statistic difference. Necrosis segments determined by cine MR significantly were less than that by TTC (P=0.0455, Kappa=0.8100). Necrosis segments determined by contrast enhanced MRI had no significant statistic difference with TTC (P=0.1573, Kappa=0.9130). Necrosis segments determined by LDDSE significantly were less than that by TTC (P= 0.0140, KappaWTBZ]=0.7000), which had significant statistic difference. Using TTC as gold standard, the sensitivity and specificity of cine MRI, contrast enhanced MRI, LDDSE, SPECT and PET in the determination of unviable myocardium were 71.43%;100%;85.71%,100%; 57.10%, 100%; 64.29%,100%and 100%,96.94%, respectively.Conclusion Cardiac MRI can combine with morphology, function and perfusion to determine viable myocardium, delineate the location and degree of necrosis myocardium clearly, demonstrate wall motion of left ventricular directly and cheaper than PET,MRI has high consistency with PET and pathology result. PET slightly overestimate extent of necrosis myocardium and can't distinguish transmural necrosis from subendocardial necrosis. ~ 201 Tl single photon emission computed tomography and low dose dobutamine echocardiography underestimate myocardial viability, which can't show extent of infarction exactly.