中文摘要：

目的探讨新型对比剂GadofluorineM（Gf）在MRI早期诊断大鼠放射性脑损伤中的应用。方法66只大鼠随机分为25、35、45、55和65Gy组，各12只，对照组6只，X射线照射构建大鼠放射性脑损伤模型，照射后1～8周行MRI平扫及Gf增强扫描，每周1次。另取12只大鼠分为55及65Gy组，每组6只，照后3—8周行钆喷酸葡胺（Gd—DTPA）增强及Gf增强扫描，每周1次。比较损伤显像时间、MRI参数和病理学改变评价放射损伤。结果25及35Gy放射组在观察2个月内MRI未发现异常信号改变，45、55及65Gy组在放射后4～6周内，T1WIGf增强扫描中逐渐出现强化改变，信号强度与对照组、25和35Gy组差异有统计学意义（F=2．15，P〈0．05），出现时间与剂量成反比（r=-0．62，P〈0．05）。Gd—DTPA增强及Gf增强扫描对比结果显示，Gd—DTPA增强扫描未发现明显改变时Gf增强可见损伤改变，Gf增强信号强度较平扫及Gd—DTPA增强明显强化（F=2．74，P〈0．01）。病理检查示65Gy组病理学检查发现部分区域出现毛玻璃样变性，其余各组均未发现明显异常。结论GadofluorineM增强改变出现在病理改变之前，可用以早期发现放射性脑损伤，较常规扫描序列及Gd—DTPA增强扫描具有明显优势。

英文摘要：

Objective To explore the value of Gadofluorine M, a novel MRI enhancement agent, in the diagnosis the early radiation brain injury. Methods Seventy-two Wistar rats were randomly divided into 5 equal groups. To establish the radiation injury model, the rat＇s posterior brain was irradiated with 0 （blank controls）, 25, 35, 45, 55, and 65 Gy, respectively. After irradiation MR plain scanning and Gadofluorine M enhancement scanning （after the TIWI and T2WI scanning Gf at the dosage of 0.1 mmol/kg was injected intravenously and scanning was performed again 12 h later） were performed once a week for 8 weeks. Another 12 rats were randomly divided into 2 equal groups to exposure to 55 and 65 Gy, respectively, and MR scanning was performed once a week for 8 weeks since the third week after MR. After T1WI and T2WI scanning Gd-DTPA was injected intravenously, MR was conducted again 30 min later, and Gf was injected intravenously （Gd-DTPAenhancement and Gf enhancement contrast）. The MR image and the pixel count were compared. Since the third week 2 rats from the Gf enhancement scanning group and 1 rat from the Gd-DTPA enhancement and Gf enhancement contrast were killed after MR with their brains taken out to undergo pathological examination. Results No abnormal signal changes were found in MRI in 25 and 35 Gy groups within 2 months after irradiation. A high signal in the Gf enhancement T1 WI image was found in 45, 55, and 65 Gy groups within the period of 4 - 6 weeks after radiation. The signal intensity was significantly higher than that of the control, 25, and 35 Gy groups（F = 2. 15, P 〈 0.05）. The emerge time of this signal was negatively correlated with the dose of radiation（ r =-0.62, P 〈 0. 05 ）. When there was no obvious change was found by Gd-DTPA enhancement, a high signal representing change of injury could be found in Gf enhancement in the same rat. The signal intensity was significantly enhanced in Gf enhancement compared to the Gd-DTPA enhancement （ F = 2.74, P 〈 0.01 ）. Histopatho