超急性期放射性肝损伤MRI菲立磁增强与照射剂量相关性研究

目的　探讨MRITSE -T2 WI菲立磁增强扫描对超急性期放射性肝损伤的诊断与评估价值。方法　 2 5只家兔随机分成 5组。除对照组外 ,其余 4组分别给予 10、2 0、3 0、40Gy单次X线半肝照射。照射后第 3天对肝区行MRITSE -T2 WI平扫及菲立磁增强扫描。分析辐照后肝组织损伤的强化特征 ,并进行组织学检查对照分析。结果　T2 WI菲立磁增强扫描在照射后第 3天能确切检出的放射性肝损伤的最小照射剂量为 3 0Gy(Ρ <0 .0 5 ) ,表现为受照区肝组织信号强度较非受照区高 ,两者间可见分界线。受照区肝组织菲立磁增强程度 (ER)的绝对值与照射剂量成正相关 (Ρ <0 .0 5 )。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≥ 2 0Gy组明显低于非受照区 (Ρ <0 .0 5 ) ,且与照射剂量成负相关 (Ρ <0 .0 5 )。结论　T2 WI菲立磁增强扫描不仅能早期发现 (照射后第 3天 )、明确诊断超急性期放射性肝损伤 ,还可通过测量肝组织ER对损伤程度进行估测。

Hyperacute Radiation-Induced Injury of Liver in Rabbits: the Correlation Between SPIO-Enhanced MR Imaging and Irradiation Dose

Objective To evaluate the correlation between the irradiation dose and superparamagnetic iron oxide (SPIO) enhanced MR imaging of the irradiated liver. Methods 25 rabbits were separated randomly into 5 groups. 3 days after focal irradiation (0, 10, 20, 30 and 40Gy), MR imaging was performed before and after SPIO injection with TSE-T 2W sequence, and the number of Kupffer cell containing SPIO particles was counted. The characteristics of MR enhancement were evaluated according to the pathological findings.Results The liver injury induced by no less than 30Gy irradiation can be detected by SPIO-enhanced T 2 weighted imaging (P<0.05). The irradiated portion of the liver was visualized with a demarcation from the non-irradiated part as a decrease in negative enhancement. Significant regression was observed as a dose-related change of the enhancement rate in the irradiated portion on SPIO-enhanced T 2-weighted images (P<0.05) and of the number of Kupffer cell containing SPIO particles (P<0.05). Conclusion MRI SPIO-enhanced T 2-weighted imaging was reliable for detecting the range and extent of liver injury 3 days after irradiation.