全脑放疗同步转移灶推量与全脑放疗加序惯推量在10例脑转移瘤转移灶放疗中的剂量学研究

Dosimetry study of SIB-IMRT and WBRT+s-IMRT in 10 patients with brain metastases

[目的]比较同步转移灶推量调强计划(SIB-IMRT)与全脑放疗加序惯推量调强计划(WBRT+s-IMRT)的靶区与危及器官的剂量学参数差异,探讨2种计划脑转移放疗的可行性.[方法]选择10例经原发灶病理学检查证实及影像学检查确诊的发现1~3个转移灶的脑转移患者.均同时给设计SIB-IMRT和WBRT+s-IMRT 2种计划.SIB-IMRT全脑照射4 000 cGY/20f(5f/w),同时给予脑转移瘤5 600 cGY/20f(5f/w);WBRT+s-IMRT全脑照射4 000 cGY/20f(5f/w)后给予脑转移瘤推量1 600 cGY/8f(5f/w).记录2种计划中靶区及危及器官的剂量学参数并进行分析.[结果] 2种计划靶区剂量分布均可满足临床要求,且均可较好地保护危及器官;SIB-IMRT靶区适形度指数明显优于WBRT+s-IMRT(P<0.001);2种计划对于脑干、眼球、视神经、视交叉的最大剂量及平均剂量间差异均无统计学意义(P>0.05),但SIB-IMRT在晶体的最大剂量明显优于WBRT+s-IMRT(P<0.05).[结论]在脑转移瘤放疗中2种计划均可满足靶区剂量要求,但SIB-IMRT较WBRT+s-IMRT有更好的靶区适形性,且在晶体保护方面具有明显的剂量学优势,是脑转移瘤放疗计划的优选方式.

OBJECTIVE To compare the target volume and the difference of dosimetry parameters of organs at risk(OAR) of two therapeutic methods simultaneous integrated boost intensity-modulated radiotherapy(SIB-IMRT) and whole brain irradiation combined with sequential intensity-modulated radiotherapy(WBRT+s-IMRT), and to explore the feasibility of two kinds of planned brain metastasis radiotherapy. METHODS 10 patients with brain metastases confirmed by pathological examination and imaging examination were selected, 1 to 3 metastases were found in each patient. All of them had two treatment plans: SIB-IMRT and WBRT+s-IMRT. In SIB-IMRT, the dose of 4 000 cGY/20f(5f/w)was given to whole brain and dose of 5 600 cGY/20f(5f/w)was simultaneously given to the brain metastases. However in the WBRT+s-IMRT, the dose of 4 000 cGY/20f(5f/w)was given to whole brain, after that the dose of 1 600 cGY/8f(5f/w)was given to brain metastases. The target volume and the difference of dosimetry parameters of organs at risk in two plans were recorded and analyzed. RESULTS The dose distribution in the target area of both treatment plans could meet the clinical needs, and both could better protect the OAR. Conformal index of target region in SIB-IMRT was better than that in WBRT+s-IMRT(P<0.001). There was no significant difference in the maximum and mean dose of brain stem, eyeball, optic nerve and optic chiasm between two plans(P>0.05). However, SIB-IMRT was better than WBRT+s-IMRT in the maximum dose to crystal(P<0.05). CONCLUSION Both plans could meet the demand for the dose of target volume in brain metastasis radiotherapy. SIB-IMRT had better target conformal than WBRT+s-IMRT, in addition, it had obvious dosimetric advantages in crystal protection and was the optimal method for radiation therapy planning for brain metastases.