容积旋转调强技术在全身放疗中运用的可行性研究

Feasibility study of volume modulated arc therapy for total body irradiation

目的探讨容积旋转调强技术(VMAT)应用于全身放疗(TBI)的剂量学特点,为临床应用提供技术参考。方法选取2012年8月至2015年1月于南京明基医院接受包含TBI清髓预处理方案的恶性血液系统疾病患者15例,采用瓦里安Eclipse 10.0计划系统,单弧360°多中心衔接的方法制定VMAT计划,处方剂量12 Gy/6f。通过分析剂量体积直方图(DVH)曲线,评估靶区、危及器官的剂量分布;通过估计治疗计划的总机器跳数、出束时间以及总治疗时间来评估计划的实施效率;最后采用Matrix X二维电离室矩阵进行剂量验证。结果 15例患者TBI计划的平均总机器跳数为(2308±210.7)MU,剂量率约400 c Gy/min,计划平均实施时间为30 min。靶区平均剂量(Dmean)为(12.58±0.45)Gy,最小剂量(Dmin)为(11.27±0.13)Gy,最大剂量(Dmax)为(15.35±0.65)Gy,并且危及器官受量较低。结论在TBI治疗中,运用VMAT技术可以获得良好的靶区剂量均匀性及计划实施效率,同时正常组织受量较低,因此有着较好的临床应用价值。

Objective To investigate the feasibility and dosimetry characteristics of a volumetric arc therapy （VMAT） technique for total body irradiation （TBI）. Methods VMAT technique was performed for fifteen patients receiving TBI therapy as a preconditioning regimen of hemapoietic stem cell transplantation at BenQ Medical Center, between Augnst,2012 and January, 2015. Eclipse 10. 0 Treatment Planning system was employed to perform treatment plan. The VMAT p/an consisted of three centers ： the head and neck, the chest and the pelvis（ each with a 360~ arcs）. The prescription dose was 12 Gy/6 f. The homogeneity of planning target volume （PTV） and organs at risk （OAR） were measured by dose volume histograms （DVH） curve. Monitor units （MU）, the bean time and total treatment time were prescribed to ensure the efficiency of the VMAT planning. Finally, the 2D ionization chamber array Matrix X was used to verify the VMAT treatment. Results In all patients, there were average MUs of （2308±210. 7）MU, and dose rate of 400 cGy/min. The total treatment delivery time was approximately 30 min. Using this technique, the average median dose for PTV was （ 12. 58±0. 45 ） Gy, with a range of（ 11.27 -± 0. 13 ） Gy to （ 5.35 ±0. 65 ） Gy. Simultaneously, a considerable OAR dose reduction of 14. 9% N 61.9% was observed by using this planning. Conclusion VMAT technique could obtain dose conformality of PTV, reduce the dose of OAR, and improve the treatment delivery efficiency. And it is expected to facilitate the clinical transition of TBI for the patients with hematologic malignancies.