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目的:研究MR钆造影剂清除差异指导脑肿瘤亚靶区勾画的可行性。方法:获取26例脑肿瘤患者Tn 2加权图像及造影剂注射5、60 min后的Tn 1加权增强图像，处理两次Tn 1加权增强图像得到含有造影剂清除差异及有无肿瘤活性信息的延迟造影剂外渗的图像。根据Tn 2加权图像有无液化坏死分为有液化坏死的A组(14例)和无液化坏死的B组(12例)，在早期Tn 1加权增强图像、Tn 1-Tn 2WI融合图像、Tn 1WI-DCEM融合图像上勾画大体肿瘤靶区(GTV)、液化坏死区(GTVn 坏死)、无液化坏死区(GTVn 无坏死)、有肿瘤活性区域(GTVn 有活性)和无肿瘤活性区(GTVn 无活性)，配对n t检验比较各亚靶区体积差异。n 结果:A组GTVn 无坏死和GTVn 坏死分别为(13.65±18.15) cmn 3和(6.30±7.57) cmn 3。GTVn 有活性为(10.40±13.52) cmn 3，GTVn 无活性为(9.55±14.57) cmn 3。A组中GTVn 无坏死比GTVn 有活性平均增加了16.3%(n P<0.05)，GTVn 无活性比GTVn 坏死平均增加了16.3%(n P<0.05)。B组中GTVn 无活性比GTVn B组平均减少了68.8%(n P<0.05)。n 结论:根据MR钆造影剂清除差异勾画的脑肿瘤亚靶区较传统单纯基于Tn 2所示坏死区域更有意义，延迟造影剂外渗的图像为脑肿瘤亚靶区的生物学精准勾画提供了依据。n “,”Objective:To evaluate the feasibility of delineating subvolume target in radiotherapy for brain tumors using Gd-based contrast clearance difference.Methods:Twenty-six patients with malignant brain tumors were scanned with MRI. The first and second acquisitions of standard Tn 2-weighted images (Tn 2WI) and Tn 1-weighted images (Tn 1WI) were performed at 5 min and 60 min after injection of contrast agent. Delayed contrast extravasation (DCEM) MRI computed by Brainlab comprised regions of contrast agent clearance representing active tumors and regions of contrast accumulation representing non-tumor tissues. Based on Tn 2WI images, 14 patients with liquefaction necrosis were divided into group A, and 12 patients without liquefaction necrosis into group B, respectively. Then, gross target volume (GTV) was delineated on Tn 1WI images. Based on the GTV, active tumor (GTVn tumor) and non-tumor regions (GTVn non-tumor) were delineated on Tn 1WI-DCEM fusion images, while liquefaction necrosis (GTVn liquefaction) and non-liquefaction (GTVn non-liquefaction) were delineated on Tn 1-Tn 2WI fusion images. Finally, the differences between different subvolumes were compared by paired n t-test.n Results:In group A, the GTVn non-liquefaction and GTVn liquefaction were (13.65±18.15) cmn 3 and (6.30±7.57) cmn 3. The GTVn tumor was (10.40±13.52) cmn 3 and the GTVn non-tumor was (9.55±14.57) cmn 3. The GTVn non-liquefaction was significantly increased by 16.3% on average compared with the GTVn tumor (n P<0.05). The GTVn non-tumor was significantly increased by 16.3% on average compared with the GTVn liquefaction (n P<0.05). In group B, The GTVn non-tumor was significantly reduced by 68.8% on average compared with the GTVn tumor (n P<0.05).n Conclusions:Compared with Tn 2WI, DCEM has advantages in identifying the liquefaction area and can clearly differentiate the subvolume of active tumors from non-liquefaction necrosis. DCEM provides evidence for guiding the delineation of subvolume in primary and metastatic brain tumors.n