摘要目的：探索弥散张量成像（ DTI）示踪视觉通路纤维束融入放疗定位CT制定保护性放疗方案的可行性。方法选取2013—2015年间本院收的31例脑胶质瘤术后拟行放疗患者。所有患者行放疗定位CT、常规平扫或增强MR及DTI检查。将获取的视觉通路纤维束DTI图像与3DT1解剖图像融合，导入TPS。采用IMRT技术分别制定将整体视觉通路纤维束作为OAR进行剂量保护方案和未考虑保护的常规方案。配对t检验两者差异。结果两种放疗计划在保证靶区照射剂量及常规OAR保护情况下，PTV的CI、HI均相近（P＝0．875、0．597）。保护性放疗方案患者患侧视束Dmax、Dmean分别降低至9．01％、9．05％，健侧17．96％、15．52％；患侧视辐射纤维束Dmax、Dmean分别降低至5．37％、5．48％，健侧12．89％、11．21％（所有P＝0．000）。结论利用DTI显示视觉通路纤维束融入放疗定位CT制定保护性放疗方案，可减少整体视觉通路纤维束的辐射剂量，从而最大程度降低放疗后发生视觉功能障碍的风险。

abstractsObjective To analyze the feasibility of incorporation of tracking visual pathway fiber bundles by diffusion tensor imaging ( DTI) in computed tomography ( CT) simulation to develop a protective radiotherapy regimen for cerebral gliomas.Methods A total of 31 patients with cerebral gliomas who were admitted to our hospital from 2013 to 2015 and planed to receive postoperative radiotherapy were enrolled as subjects.All patients underwent CT simulation, conventional or contrast-enhanced magnetic resonance imaging, and DTI.The obtained DTI images of visual pathway fiber bundles were fused with 3DT1 anatomical scans and then imported into the treatment planning system.A protective treatment plan ( setting the entire visual pathway fiber bundles as organs at risk (OARs)) and a conventional treatment plan were made for intensity-modulated radiotherapy ( IMRT) .Comparison of treatment outcomes was made by paired t test.Results There were no significant differences in the conformity index and heterogeneity index of the planning target volume between the two treatment plans ( P=0.875,0.597), both of which had sufficient radiation doses to the target volume and conventional OARs protected.For the patients undergoing the protective treatment plan, the Dmax and Dmean values were reduced to 9.01%and 9.05%, respectively, in the ipsilateral optic tract and to 17.96%and 15.52%, respectively, in the contralateral optic tract;the Dmax and Dmean values were reduced to 5.37%and 5.48%(P=0.000), respectively, in the ipsilateral optic radiation tract and to 12.89%and 11.21%( P=0.000) , respectively, in the contralateral optic radiation tract.Conclusions The protective treatment plan based on CT simulation combined with the display of visual pathway fiber bundles by DTI can reduce the radiation dose to the entire visual pathway fiber bundles, which keeps the risk of visual dysfunction after radiotherapy as low as possible.