家兔超急性期放射性肝损伤MRI表现与病理对照研究

目的　探讨超急性期放射性肝损伤MRI表现及其病理基础 ,评估MRI平扫及菲立磁增强扫描检出放射性肝损伤的时间效能。材料与方法　 18只家兔随机分成 3组后均给予 4 0Gy单次X线半肝照射 ,第 1组于照射后第1d、第 2、3组分别于照射后第 2、3d行肝区MRITSE T2 WI及TSE T1WI两个序列的平扫及菲立磁增强扫描 ,同时取材做组织学检查。对MRI表现与病理组织学检查结果进行对照分析。结果　所有家兔T2 WI及T1WI平扫、T1WI菲立磁增强扫描肝组织信号强度均未发现变化。T2 WI菲立磁增强扫描对放射性肝损伤的检出时间为照射后第 3d(P <0 .0 1) ,表现为肝组织信号强度受照区与非受照区均较T2 WI平扫时降低 ,但受照区肝组织信号强度较非受照区高 ,两者间可见分界线。所有家兔受照区肝组织在光镜下未见明确组织水肿、纤维化及炎症细胞浸润等病理征象 ,但其单位视野面积内含有SPIO颗粒的Kupffer细胞数在照射后第 3d明显低于非受照区 (P <0 .0 1)。电镜下 ,照射后第 3d的受照区肝细胞及Kupffer细胞内见线粒体明显肿胀伴局部空泡样变。结论　T2 WI菲立磁增强扫描在照射后短时间内 (照射后第 3d)即可检出超急性期放射性肝损伤 ,并能提供直观、精细的影像学依据

The Hyperacute Radiation-induced Injury of Liver in Rabbits:The Relationship between MR Imaging and Histopathologic Results

Objective To discuss the MR imaging of hyperacute radiation induced injury of liver and pathological basis in rabbit, and to evaluate the efficacy with pre and post superparamagnetic iron oxide (SPIO) contrast enhanced MR imaging.Materials and Methods 18 rabbits were separated randomly into 3 groups. After focal irradiation (40 Gy) 1 day in group 1, 2 days and 3 days later in group2 and 3 respectively. MR imaging was performed before and after SPIO injection with TSE T 2W, TSE T 1W sequences, and the specimens were obtained. The MR imaging features of hyperacute radiationinduced liver injury were evaluated and correlated to the pathological findings.Results The signal intensities of irradiated and nonirradiated liver were not only normal and uniform on T 1 weighted and T 2 weighted images before SPIO enhanced, but also on SPIO enhanced T 1 weighted images. Though decreased in both liver portions on SPIO enhanced T 2 weighted images, the signal intensity of the irradiated portion was higher than the nonirradiatedpart, and the margins between them were demarcated. No evidence of edema, fibrosis, congestion, infiltration of inflammatory cells in all specimens was found by light microscopy, nevertheless, the number of Kupffer cell containing SPIO particles in the irradiated liver were markedly less than in the nonirradiated liver in the third day after irradiation (P<0.01). Furthermore, the swelling of mitochondria and vacuolization in the hypatocytes and Kupffer cells of the irradiated liver in the third day were found by the electron microscopy.Conclusion MRI SPIO enhanced T 2 weighted imaging can detect the hyperacute injury of radiation on the liver after irradiation in very short time (3 days).