基于TOMO计划系统的全骨髓放疗计划最佳优化参数和剂量学递增研究

Study on the best optimization parameters and dose escalation of TOMO-based total marrow irradiation plan

目的:选择基于TOMO计划系统的全骨髓放疗计划的最佳优化参数组合,并进行剂量学递增研究。方法:选取2016年至2019年郑州大学第一附属医院放疗中心收治的10例急性淋巴细胞白血病患者,年龄5~12岁。处方剂量方案为12 Gy/6F,危及器官包括晶体、眼球、腮腺、心脏、肺、肾、胃、肝、小肠等。随机选取一例患儿进行参数优化。设计基于TOMO计划系统的3个优化参数[射野宽度(1.0、2.5、5.0 cm)、螺距(0.143、0.287、0.430)和调制因子(2.0、2.5、3.0)]的全骨髓放疗计划,统计危及器官的照射剂量、靶区的均匀性指数(HI)、出束时间以及机架周期。采用最佳优化参数,对全骨髓照射计划进行5种不同剂量级别(12、14、16、18和20 Gy)的剂量学研究,使全骨髓照射最大剂量时的危及器官照射剂量维持在全身照射方案12 Gy以下或者相近的剂量水平,绘制剂量体积直方图。结果:基于TOMO计划系统的全骨髓放疗计划的最佳优化参数为射野宽度5.0 cm,螺距0.287,调制因子3.0。采用最佳优化参数,全骨髓照射剂量为16 Gy时,肺平均照射剂量为8.40 Gy,其余危及器官照射剂量均低于全身照射的12 Gy水平;全骨髓照射剂量递增到18、20 Gy时,肺平均照射剂量分别为9.45、10.49 Gy,其余危及器官照射剂量均低于全身照射的12 Gy水平。结论:采用最佳优化参数,可以将全骨髓照射剂量提高到16 Gy。

Aim:To optimize the parameters combination of TOMO-based total marrow irradiation(TMI)plan and conduct a dose escalation study based on the optimized parameters.Method:Ten patients with acute lymphocytic leukemia(ALL)admitted to Center of Radiation Therapy,the First Affiliated Hospital of Zhengzhou University from 2016 to 2019 were selected.The age of the patients was 5-12 years.The prescription dose was 12 Gy/6F,and the organs at risk included lens,eyeballs,parotid glands,heart,lungs,kidneys,stomach,intestine,liver,etc.One patient with ALL was chosen,and the TMI plan based on 3 parameters[field width(1.0,2.5,5.0 cm),pitch(0.143,0.287,0.430)and modulation factor(2.0,2.5,3.0)]of TOMO treatment planning system were designed,and the dose of the organs at risk,the homogeneity index(HI)of the target,the beam time,and the rack cycles were counted.Using the best optimized parameters,5 different dose levels of 12,14,16,18,20 Gy were designed for these 10 patients with ALL;meanwhile,the amount of organ at risk was maintained within 12 Gy range of the total body irradiation(TBI).Finally,dose-volume histogram was drawn.Results:The optimal parameters of TMI plan were field width of 5.0 cm,pitch of 0.287,and modulation factor of 3.0.When the TMI dose increased to 16 Gy,the average lung dose was 8.40 Gy,and the dose of the other organs at risk were lower than the TBI of 12 Gy.When the TMI dose increased to 18,20 Gy,the lung dose was 9.45 Gy and 10.49 Gy,and the dose of the other organs at risk were lower than the TBI of 12 Gy.Conclusion:Based on the best optimizing parameters,the dose of TMI could be increased to 16 Gy.