三维适形放疗后免VX2肝癌MR灌注加权成像：与病理对照

目的分析兔VX2肝癌行三维适形放疗（3DCRT）后MR灌注参数及相关病理变化，探讨MR灌注加权成像（PWI）作为肝肿瘤临床诊断、术后监测及疗效评估的可行性。方法新西兰大白兔13只，采用组织块种植的方法制成肝VX2模型，每只荷瘤兔行单次3DCRT。使用Philips1．5TMR扫描仪，采用EPI—SE序列、SENSE技术，于放疗前、后10天对13只荷瘤兔分别行MR灌注加权成像及增强扫描。选取病灶与周围正常肝组织的感兴趣区（ROI），分别测量血流灌注值。PWI采用信号强度一时间曲线的最大信号下降斜率（SRSmax）作为定量指标，标本行血管内皮生长因子（VEGF）检测，并与PWI结果进行对照，分析不同ROI的SRSmax变化规律。结果放疗后肿瘤中央区及周边区SRSmax值均较放疗前降低f尸〈0．05），瘤周正常肝实质区SRSmax值无明显差异，不同ROI的SRSmax下降程度与VEGF破坏程度及范围一致（r=0．487，P=0．01）。结论PWI能反映兔VX2肝癌放疗后微循环及血流动力学变化，SRSmax可作为活体肿瘤微血管的一种评价指标。

Perfasion-weighted imaging of rabbit models with hepatic VX2 tumor after three-dimensional conformal radiotherapy: compared with pathological changes

Objective： To analyze the perfusion parameters and related pathological changes of rabbit VX2 liver cancer after three-dimensional conformal radiotherapy （3DCRT） and discuss the availability of perfusion-weighted imaging （PWI） as a clinical diagnosis of liver tumors, postoperative monitoring and efficacy evaluation. Materials and Methods： Of 13 New Zealand rabbits were implanted in liver with VX2 tumor by tissue block, each rabbit was treated by single 3DCRT. All of them were performed PWI and enhanced scanning 10 days before and after the radiotherapy by using a 1.5T MR scanner with EPI-SE sequence and SENSE technology. Finally, image quality of 3 rabbits were not good enough, 13 were enrolled into statistic. Selecting the regions of interests （ROI） of lesions and surrounding normal liver tissue, perfusion values were measured and statistically analyzed. Maximal signal reduction slope （SRSmax） of the signal intensity versus time curves were created as quantitative index, specimens of vascular endothelial growth factor （VEGF） were examined and compared with the perfusion-weighted images. Results： After radiotherapy, the SRSmax value of central and surrounding of tumor were statistically decreased than that before radiotherapy （P〈0.05）, but there were no differences in normal liver parenchyma of tumor border; the SRSmax decreasing of different ROI was accordant to the range of the spoiled vascular endothelial growth factor （r=0.487, P=0.01）. Conclusion： PWI can reflect the microcirculation and hemodynamic changes of rabbit models with hepatic VX2 tumors after 3DCRT. SRSrnax can be used as an evaluating indicator for living tumor microvessels.