摘要目的 用粉末热释光剂量计(TLD)和胶片测量调强放疗(IMRT)光子线束吸收剂量和二维剂量分布验证研究.方法 用国际原子能机构(IAEA)提供的聚苯乙烯固体模体,经CT扫描,影像传给放射治疗计划系统(TPS)制定放疗计划,源皮距90 cm,深度10 cm,照射野5 cm×5 cm,计算吸收剂量6 Gy相应的监督单位(MU).根据四川省各个地域医疗水平、放射治疗开展情况和物理师技术力量等因素选择了7家三级甲等医院,每家医院选取1台常用的加速器,7台加速器生产厂家分别为瓦里安、医科达和西门子,并分别实施调强放疗计划.医院使用的均质固体模体,尺寸30 cm×30 cm,25 cm×25 cm的胶片放在模体上,厚度＞20 cm的固体模体板覆盖在胶片上面,射线束中心对准胶片中心,实施调强放疗计划的验证.结果 7台加速器中,TLD吸收剂量与TPS计划剂量相对偏差分别为1.4％、3.7％、-2.5％、-0.3％、4.9％、4.9％和5.0％,满足IAEA要求的±5％以内;胶片吸收剂量与TPS计划剂量相对偏差分别为4.7％、4.3％、1.5％、3.9％、-1.6％、3.3％和-1.3％,满足IAEA要求的±5％以内;5台加速器胶片二维剂量分布3 mm/3％通过率分别为99.9％、98.5％、98.5％、97.9％和70.0％,其中4台加速器满足IAEA要求的通过率为90％以上,1台不满足要求.结论 用TLD和胶片测量调强放疗光子线束野吸收剂量和二维剂量分布验证,科学实用,经济方便,可为放射治疗计划提供质量保证.

abstractsObjective To measure absorbed dose and verify two-dimensional dose distribution from IMRT MLC using thermoluminescence dosimeters (TLDs) and films.Methods The teflon phantom was scanned by CT and its images were transmitted to TPS for planning.The 6 Gy-corresponding MUs were calculated at 90 cm SSD and 10 cm depth and on 5 cm × 5 cm radiation field.All the plans were implemented at 7 medical linear accelerators,which were produced by Varian,Elekta and Siemens and selected from 7 third-grade first-class hospitals according to the technical conditions of various regions in Sichuan province.The homogeneous solid phantoms used in hospitals were covered by 30 cm × 30 cm and 25 cm × 25 cm films.Then,the films were covered by thicker-than-20 cm phantoms.Finally,the plans were implemented by aligning the center of beams to the films center.Results The relative deviations of the measured absorbed dose to TPS-planned dose were 1.4％,3.7％,-2.5％,-0.3％,4.9％,4.9％,5.0％ for TLDs and 4.7％,4.3％,1.5％,3.9％,-1.6％,3.3％,-1.3％ for films,respectively,all consistent with the limit of less than 5％.The passing rates of 2D dose distribution (3 mm/3％) were 99.9％,98.5％,98.5％,97.9％ and 70.0％ for 5 accelerators,with only one not consistent with the requirements.Conclusions It is convenient to measure the absorbed dose to photon beam field and verify two-dimensional dose distribution using TLDs and films,which can provide quality assurance for radiation treatment plans.