电离室灵敏体积对射波刀计划绝对剂量验证的影响  

Effect of ion chamber sensitive volume on absolute dose verification in CyberKnife plan

作　　者：梁志文[1] 杨晶[1] 杨志勇[1] 胡斌[1] 程军平[1] 李勤[1] 伍钢[1] Liang Zhiwen Yang Jing Yang Zhiyong Hu Bin Cheng Junping Li Qin Wu Gang(Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430023, Chin)

机构地区：[1]华中科技大学同济医学院附属协和医院肿瘤中心,武汉430023

出　　处：《中华放射肿瘤学杂志》2017年第7期786-789,共4页Chinese Journal of Radiation Oncology

基　　金：国家重点研发计划数字化诊疗装备研发专项（2016YFC0106700）

摘　　要：目的 研究电离室灵敏体积对射波刀计划绝对剂量验证的影响.方法 CT扫描固体水模体后将影像导入计划系统,选用可变孔径准直器分别设计单野照射、多野等中心照射和非等中心适形计划.使用灵敏体积为0.007 cm3（ExradinA16）、0.240 cm3（ExradinA12s）和0.600 cm3（PTW30013）的电离室在固体水中分别测量各计划的绝对剂量,并计算相对误差.结果 单野照射计划的相对误差随准直器孔径缩小而增加,相对误差在±2%内的最小准直器孔径分别为12.5 mm （ExradinA16）、25.0 mm （ExradinA12s）和30.0 mm （ExradinPTW30013）;多野等中心照射计划测量中的相对误差为（0.26±3.9）%（ExradinA16）、（-6.28±14.33）%（ExradinA12s）和（-9.41±14.10）%（PTW30013）;使用15.0 mm和7.5 mm准直器设计的非等中心适形计划相对误差分别为（0.79±1.43）%和（2.01±8.39）%.临床计划的绝对剂量验证中3种电离室测量的数据差异无统计学意义（P=0.985）.结论 在较大准直器孔径情况下,若处方剂量完全包绕电离室灵敏体积则灵敏体积对测量结果影响不大.Objective To evaluate the effect of ion chamber sensitive volume on absolute dose verification in CyberKnife plan.Methods Solid water phantoms were scanned by a CT scanner, single-field plan, multi-field isocentric plan and sequential optimized plan were designed by the treatment planning system.Absolute doses were measured at the specified point in each plan using the ion chambers with sensitive volumes of 0.007 cm3（A16）, 0.24 cm3（A12 s）, and 0.6 cm3（PTW30013） and compared with calculated values.Results For the single-field plan, the relative error increased as the aperture size of collimator decreased;with relative errors within ±2%, the smallest aperture sizes of collimator were 12.5 mm （A16）, 25 mm （A12 s）, and 30 mm （PTW30013）.For the multi-filed isocentric plan, the relative errors were 0.26%±3.90%（A16）,-6.28%±14.33%（A12 s）, and-9.41%±14.10%（PTW30013）.For the sequential plan optimized with 15 mm cone, the relative error was 0.79%±1.43%;for the sequential plan optimized with 7.5 mm cone, the relative error was 2.01%±8.39%.In absolute dose verification for clinical plans, there was no significant difference between the results measured by these ion chambers （P=0.985）.Conclusions There is no significant effect of ion chamber sensitive volume on absolute dose verification in CyberKnife plan under the following two situations：（1） the collimator with a relatively large aperture is used;（2） the sensitive volume of ion chamber is totally covered by the prescription isodose line.

关 键 词：射波刀 吸收剂量 质量保证 电离室 

分 类 号：R730.55[医药卫生—肿瘤]