基于治疗室CT分析前列腺癌碳离子治疗前剂量分布的鲁棒性

Study of robust of dose distribution of prostate cancer before carbon ion treatment based on in-room CT

目的分析前列腺癌碳离子放射治疗前,原计划套用治疗室CT后临床靶区(CTV)的剂量和正常组织耐受剂量的鲁棒性。方法回顾性收集2020年1月—2021年6月在上海市质子重离子医院进行碳离子治疗的前列腺癌患者30例,用简单随机法选取每位患者治疗前的5次治疗室CT图像,将最初治疗计划套用治疗室CT重新计算剂量分布,获取剂量体积直方图(DVH)参数,计算CTV的95%、90%剂量对应的体积百分数V95%、V90%及直肠的80%剂量对应的体积V80%,与最初计划的剂量学参数进行比较,采用配对或两个独立样本t检验进行统计分析。结果套用治疗室CT重新计算剂量分布,CTV的V95%、V90%和直肠的V80%的平均值分别是98.1%±1.2%、99.9%±0.2%、(5.8±1.6)ml,与最初治疗计划相比差异有统计学意义(P<0.001,P=0.001,P<0.001)。符合计划实施标准V95%≥95%、V90%≥98%、直肠V80%<10 ml的次数分别为148次(98.7%)、150次(100.0%)、147次(98.0%)。结论基于治疗室CT分析,在采用本研究中心的患者管理方式和定位方式的情况下,前列腺癌碳离子治疗的全过程靶区剂量和正常组织剂量不确定性小、鲁棒性好。

Objective To analyze the robustness of the dose of clinical target volume(CTV)and tolerance dose of normal tissues after applying in-room CT before carbon ion radiotherapy for prostate cancer.Methods Thirty prostate cancer patients treated with carbon ion in Shanghai Proton and Heavy Ion Center from January 2020 to June 2021 were enrolled in this study.Five in-room CT images of each patient were selected randomly before treatment.Dose distributions were recalculated using the original plan on in-room CT images and dose volume histogram(DVH)parameters were obtained,including V95%and V90%of CTV and V80%of rectum.The values were compared with the dosimetric parameters of the original plan.Statistical analysis was performed by paired or two independent samples t-tests.Results The dose distribution was recalculated by applying in-room CT.The mean values of V95%and V90%of CTV and V80%of rectum were 98.1%±1.2%(P<0.001),99.9%±0.2%(P=0.001)and(5.8±1.6)ml(P<0.001),respectively.The differences were statistically significant compared with those of the original plan.The frequency of V95%≥95%,V90%≥98%of CTV,and V80%<10 ml of rectum was 148(98.7%),150(100.0%)and 147(98.0%),respectively.Conclusion Based on in-room CT analysis and the patient management and positioning methods of our research center,the uncertainty of target dose and normal tissue dose in the entire process of prostate cancer carbon ion therapy is small,and the robustness is good.