探讨靶区处方剂量50%生成区域的平均γ值在Compass三维剂量验证中的应用  

Discussion on application of mean gamma index to Compass 3D dose verification in target area receiving 50%of prescribed dose

作　　者：郑倩倩 曹婧 曲荣荣 高文超 陈文彰 Zheng Qianqian;Cao Jing;Qu Rongrong;Gao Wenchao;Chen Wenzhang(Department of Radiation Oncology,Shijingshan Teaching Hospital of Capital Medical University,Beijing Shijingshan Hospital,Beijing 100043,China;Department of Radiation Oncology,Fifth Medical Center of Chinese PLA General Hospital,Beijing 100071,China)

机构地区：[1]首都医科大学石景山教学医院北京市石景山医院放疗科,北京100043 [2]解放军总医院第五医学中心放疗科,北京100071

出　　处：《中华放射医学与防护杂志》2023年第6期469-474,共6页Chinese Journal of Radiological Medicine and Protection

摘　　要：目的探讨Compass剂量验证系统在基于模型计算剂量和基于测量重建剂量的容积旋转调强放射治疗(VMAT)计划验证中,使用50%靶区处方剂量区平均γ值作为计划验证参考指标的应用价值。方法基于Compass剂量系统用两种方法对70例患者的VMAT计划进行剂量验证,得到每例VMAT计划验证中50%靶区处方剂量区的平均γ值和γ通过率,评估50%靶区处方剂量区的平均γ值在剂量验证中的应用价值。先将计划系统(TPS)计算得到的计划信息导入到Compass系统中,进行基于加速器数据模型的独立核算剂量计算,得到基于模型独立核算的三维剂量。再将每例患者的治疗计划在加速器下实测得到的计划通量通过Compass系统进行剂量重建,得到基于测量重建的三维剂量。将两种方法得到的三维剂量分布结果与TPS计算得到的结果进行比较。结果结合γ分析误差设定条件为3%/3mm标准的γ通过率结果,对50%靶区处方剂量区的平均γ值进行评估,γ≤0.4为通过,0.4<γ≤0.6为临床可接受结果,γ>0.6为不通过。70例VMAT计划验证结果显示,基于模型独立核算和TPS计算结果具有较好的一致性,γ值均<0.6,其中γ≤0.4的67例,0.4<γ≤0.6的3例,γ通过率均>92%;基于测量重建体内三维剂量的结果略差于基于模型的计划结果,γ值均<0.6,其中γ≤0.4的35例,0.4<γ≤0.6的35例,γ通过率均>88%,其中68例通过率>90%,2例<90%,但都符合临床剂量验证要求。基于模型的独立核算剂量分布结果优于基于测量重建剂量的结果,差异有统计学意义(t=15.20、10.71,P<0.05)。结论50%靶区处方剂量区的平均γ值可作为临床计剂量验证参考指标判断临床计划的可执行性,平均γ值结合γ通过率的综合结果共同对剂量验证进行评估更有说服力;基于模型的剂量验证省时省力,但需要与基于测量的验证方式相结合进行综合考虑,作为一种可靠的剂量验证方法应用到临床。Objective To explore the value of using the mean gamma index(GI)in targer area receiving 50%prescribed dose as reference in VMAT planned dose verification through model-based dose calculation and measurement-based dose reconstruction.Methods Based on Compass dose verificantion system,the VMAT plans for 70 patients were validated using two method.The mean GI and passing rate in target area receiving 50%of prescribed dose area for each validation plan were obtained to evaluate its application value in dose validation.First,plan information obtained by TPS calculation was input into the Compass system for performing independent dose calculation based on the accelerator data model,and obtain a three-dimensional dose based on the independent model calculation.The planned fluence measured for each patient's treatment plan on the accelerator was reconstructed through the Compass system to obtain a three-dimensional dose based on measurement reconstruction.The three-dimensional dose obtained by the two method were compared with the three-dimensional dose calculated by TPS.Results Combined with the gamma criteria of 3%/3 mm in the error setting condition of GI analysis,the mean GI in the area receiving 50%of prescribed dose was evaluated.GI≤0.4 was classified as PASS,0.4<GI≤0.6 as being clinically acceptable,and GI>0.6 as FAIL.The VMAT planned dose verification for 70 patients showed that the model-based independent calculation was in a better agreement with the TPS calculation.The GI values were all<0.6:GI≤0.4 for 67 patients and 0.4 in-vivo measurement-based reconstructed 3D dose are slightly lesser than the model-based planed result;theGI values were all<0.6:GI≤0.4 for 35 patients and 0.4<GI≤0.6 for other 35 patients,with gamma pass rate larger than 88%,of which gamma passing rate>90%for 88 patients and<90%for other 2,all meeting the requirements of clinical dose verification.The model-based independent dose verification is better than the measurement-based reconstructed dose verificantion,and the difference

关 键 词：COMPASS 三维剂量验证 平均γ值 重建剂量 

分 类 号：R730.55[医药卫生—肿瘤]