CAJ | 학술논문

目的探讨Hi-ART螺旋断层治疗机照射野剂量学参数测量的内容和方法.方法用断层治疗机专门配置的微型扫描水箱在治疗条件下测量了6 MV X线的百分深度剂量和射野离轴比,并与常规Primus加速器6 MV X线进行比较.根据AAPM TG51号报告用Tomotrometer剂量仪和A1SL电离室在源皮距85 cm、照射野40 cm×5 cm、1.5 cm深度条件下对断层治疗机进行输出剂量刻度,并对剂量线性和重复性进行测量分析.输出剂量率随机架角的变化分别用0.6 cm3电离室和Unidos剂量仪在直径为3 cm有机玻璃体模中测量和用治疗机自身的MVCT探测器测量.设置不同的照射范围,在固体水组织等效材料中对多叶准直器照射野输出因子进行测量.结果 Hi-ART断层治疗机6 MV X线百分深度剂量的最大剂量点在1.0 cm左右.Hi-ART断层治疗机和Primus 6 MV X线在源皮距85 cm、深度10 cm处的百分深度剂量分别为59.6%和64.7%.单个照射野内剂量分布是不均匀的,在人体左右方向剂量分布呈锥形,在人体头脚方向剂量分布和照射野的宽度有关,40 cm×5 cm照射野的输出剂量率为848.38 cGy/min.剂量仪的读数R和照射时间t的关系为R=-0.017+0.256t,线性相关系数为0.999.重复测量的输出剂量率的最大偏差为1.6%,标准偏差＜0.5%;输出剂量率随机架角度变化的最大偏差为1.1%,标准偏差＜0.5%.多叶准直器相邻叶片对单个叶片照射野的剂量贡献比较大,继续增加叶片数目输出因子基本保持不变.结论 Hi-ART断层治疗机的输出剂量率高,照射野剂量分布不均匀.独特的设计和剂量学特性使其剂量计算模型和调强实现方式更加简单、高效.
목적 탐토Hi-ART라선단층치료궤조사야제량학삼수측량적내용화방법.방법 용단층치료궤전문배치적미형소묘수상재치료조건하측량료6 MV X선적백분심도제량화사야리축비,병여상규Primus가속기6 MV X선진행비교.근거AAPM TG51호보고용Tomotrometer제량의화A1SL전리실재원피거85 cm、조사야40 cm×5 cm、1.5 cm심도조건하대단층치료궤진행수출제량각도,병대제량선성화중복성진행측량분석.수출제량솔수궤가각적변화분별용0.6 cm3전리실화Unidos제량의재직경위3 cm유궤파리체모중측량화용치료궤자신적MVCT탐측기측량.설치불동적조사범위,재고체수조직등효재료중대다협준직기조사야수출인자진행측량.결과 Hi-ART단층치료궤6 MV X선백분심도제량적최대제량점재1.0 cm좌우.Hi-ART단층치료궤화Primus 6 MV X선재원피거85 cm、심도10 cm처적백분심도제량분별위59.6%화64.7%.단개조사야내제량분포시불균균적,재인체좌우방향제량분포정추형,재인체두각방향제량분포화조사야적관도유관,40 cm×5 cm조사야적수출제량솔위848.38 cGy/min.제량의적독수R화조사시간t적관계위R=-0.017+0.256t,선성상관계수위0.999.중복측량적수출제량솔적최대편차위1.6%,표준편차＜0.5%;수출제량솔수궤가각도변화적최대편차위1.1%,표준편차＜0.5%.다협준직기상린협편대단개협편조사야적제량공헌비교대,계속증가협편수목수출인자기본보지불변.결론 Hi-ART단층치료궤적수출제량솔고,조사야제량분포불균균.독특적설계화제량학특성사기제량계산모형화조강실현방식경가간단、고효.
Objective To develop a measurement method of dosimetric parameters for Hi-ART tomotherapy unit. Methods Percentage depth doses and beam profiles were measured using the dedicated mini water phantom, and compared to the results of 6 MV X-ray from Primus accelerator. Following the AAPM TG51 protocol, absolute dose calibration was carried out under SSD of 85 cm at depth of 1.5 cm for field of 5 cm ×40 cm. The output linearity and reproducibility were evaluated. The output variation with the gantry rotation was also investigated using 0.6 cm3 ion chamber in cylindrical perplex phantom and on-board MVCT detectors. Leaf fluence output factors were quantified for the leaf of interest and its adjacent leaves.Results The buildup depth was around 1.0 cm. The PDD values at 10 cm for Hi-ART and Primus were 59.7% and 64.7%, respectively. Varying with the field width, the lateral and longitudinal beam profiles were not so homogeneous as the Primus fields. The measured dose rate was 848.38 cGy/min. The fitted lint(sec) ,with a relative coefficient of 0. 999. The maximum deviation and standard deviation of output were 1.6% and less than 0.5% ; The maximum deviation and standard deviation of output changed by gantry angle were 1.1% and 0.5 % , respectively. Leaf fluence output factors did not increase significantly when leaves were opened beyond the two adjacent leaves. Conclusions Hi-ART Tomotherapy unit has a very high dose output and inhomogeneous beam profiles owing to its special design of the treatment head. This may be useful in dose calculation and treatment delivery.