恶性脑胶质瘤三维适形放疗与调强适形放疗剂量学对比研究

The dosimetric comparation of malignant glioma between the 3D-CRT and the IMRT

背景与目的:恶性胶质瘤细胞对射线敏感性低,增加肿瘤区的放射剂量可能进一步延长局控和生存期。然而由于正常组织耐受量限制,普通三维适形技术(3 dimensional convention radiation therapy,3D-CRT)难以进一步提高剂量,本研究旨在利用三维治疗计划系统(3 dimensional treatment planning system,3D-TPS)对恶性脑胶质瘤3D-CRT和逆向调强适形放疗(intensity modulated radiation therapy,IMRT)计划作剂量学比较,探讨IMRT在恶性脑胶质瘤放疗中应用的可行性,为临床应用IMRT技术提高恶性脑胶质瘤靶区剂量提供理论基础。方法:选择2006年7月-2007年10月本科收治的11例经病理证实的恶性胶质瘤术后患者,分别用3D-TPS对每例患者做出3D-CRT和IMRT计划。比较两种方法中靶区覆盖情况、适形指数、危及器官所受照射剂量、照射范围以外正常组织的剂量差别。结果:IMRT计划中PGTV的Dmean、PTV1和PTV2的Dmax和Dmin均高于3D-CRT(P<0.05)、靶区适形度更好(CI95%1.39vs2.74,P<0.001),脑干、垂体、晶体、双眼、视交叉、右侧视神经的照射剂量、照射靶区以外正常组织总体及25～30Gy受照积分剂量低于3D-CRT(P<0.05);两种计划对肿瘤靶区范围的覆盖(P=0.70)及靶区剂量均匀性(P=0.41)、左侧视神经受量(P=0.08)、小于25Gy的靶区外正常组织积分剂量IMRT略高于3D-CRT,差异无显著性(P>0.05)。结论:与3D-CRT比较IMRT能够提高靶区适形度及肿瘤放疗剂量、更好的保护危及器官、有效提高治疗增益比、且没有提高暴露在低剂量照射范围内的正常组织的体积和总体剂量,缩短了治疗时间。

Background and purpose： Malignant gliomas are not very sensitive to radiation .One has to escalate the dose in order to prolong survival. But due to restraint of the normal tissues, total dose can no be raised to a higher level when using 3D-CRT. We compared the difference between the 3D-CRT and the IMRT of patients with malignant glioma by 3DTPS. Methods： From July. 2006 to Oct. 2007, we separately designed 11 malignant glioma patients＇ plan by IMRT and 3D-CRT. We compared the difference between the two kinds of plan in V90, V95, Dram, D D and CI of the target volume, and the Dmax and Dmean of normal tissues as well as ID of nontarget normal tissue. Results： The dose coverage rate of PTV 1, PTV2 ,dose of left optic nerve and ID of low dose region（0.5-25 Gy） about the non-target normal tissue in the IMRT plan was comparable to the 3D-CRT with no statistical difference in dosimetry comparison. However, there was obvious difference in PGTV, CI（95%1.39 vs 2.74 P〈0.001）, D of PGTV, Dmax and Dmin of PTV1 and PTV2,ID of total non-target normal tissue and some normal tissues between IMRT and 3D-CRT. Conclusion： Both IMRT and 3D-CRT plan have good coverage of the primary tumor. IMRT can give higher dose to the tumor and spare the normal tissue from high dose irradiation. It is a good selection for malignant glioma patients.