江苏省8台加速器调强放射治疗多叶光栅叶片到位精确度验证方法研究  

Verification of positioning accuracy of MLC leaves of 8 medical accelerators in IMRT in Jiangsu province

作　　者：杨春勇[1] 曹兴江[1] 周媛媛[1] 张乙眉[1] 王进[1] Yang Chunyong;Cao Xingjiang;Zhou Yuanyuan;Zhang Yimei;Wang Jin(Department of Radiation Protection,Jiangsu Provincial Center For Disease Control and Prevention,Naajing 430079,China)

机构地区：[1]江苏省疾病预防控制中心放射防护所,南京430079

出　　处：《中华放射医学与防护杂志》2019年第2期128-131,共4页Chinese Journal of Radiological Medicine and Protection

基　　金：IAEA资助项目(17821/CRP).

摘　　要：目的用胶片(film)测量调强放射治疗(IMRT)多叶光栅(MLC)叶片到位精确度验证方法研究。方法固体均质模体30cm×30cm,经CT扫描,影像传给放射治疗计划系统(TPS)制定治疗计划,多叶光栅片形成5条栅栏野条状,每条条状栅栏野长3cm,宽0.6cm,条状与条状之间距离3cm,在最大剂量点(dmax)处,源皮距离100cm,6MVX射线,每条条状照射监督单位250MU。25cm×25cm的放射性免冲洗胶片EBT2放在30cm×30cm均质固体模体上,厚度1.0cm的固体模体板覆盖在胶片上面,实施调强放射治疗计划照射。结果7台加速器胶片测量与TPS计划每条栅栏野MLC位置偏差≤±0.5mm,符合要求,1台加速器结果为-0.6mm,不符合要求。胶片测量每对与所有多叶光栅叶片位置偏差结果,8台医用加速器结果均符合要求。4台加速器胶片测量每对与每条所有多叶光栅实际宽度差值≤±0.75mm,符合要求,3台加速器结果超出±0.75mm,不符合要求。6台加速器胶片测量每对与每条所有多叶光栅实际宽度标准偏差≤0.3mm,符合要求,2台加速器结果超出0.3mm,不符合要求。结论胶片剂量学验证调强放射治疗多叶光栅到位精度方法简单可靠,能满足检测的要求,是调强放射治疗质量控制的重要内容。Objective To measure the accuracy of multi-leaves collimator (MLC) leaves positions in intensity modulated radiation therapy (IMRT) for verification purpose. Methods Solid water homogeneous phantom with size of 30 cm×30 cm was scanned by CT scanner. The scanned images were delivered to radiation therapy plan system (TPS) to formulate the therapy plan. The MLC leaves created 5 strips of exposure field, each 3 cm long and 0.6 cm wide. The strip-to-strip distance was 3 cm. With 6 MV X-rays, the SSD was 100 cm at the maximum dose point. The MU per strip was 250 MU. EBT2 radiochromic films each of 25 cm×25 cm were placed on the 30 cm×30 cm homogeneous solid phantom and covered with 1 cm thick solid phantom slabs for delivering of IMRT. Results For 7 of 8 accelerators, the differences of film-measured and TPS-planned MLC leaf position for every fence field were within ± 0.5 mm as required by IAEA, with only other one being -0.6 mm, not consistent with the IAEA requirements. The film-measured position difference between each pair and all pairs of leaves for 8 accelerators were all in line with IAEA′s requirements. The film-measured actual width difference between each pair and all pairs of leaves was within ±0.75 mm as required by IAEA for 4 accelerators and outside ±0.75 mm for the other three, not consistent with the IAEA requirements. The standard deviation of film-measured actual width between each pair and all pairs of leaves for 6 accelerators were ≤0.3 mm, as required by IAEA, whereas >0.3 mm for the other two, not consistent with IAEA requirements. Conclusions The film dosimetric verification of IMRT is an important part of its quality assurance, featuring simple, reliable and highly accurate positioning and can meet measurement requirement.

关 键 词：调强放射治疗 多叶光栅叶片 到位精确度 质量核查 

分 类 号：R730.55[医药卫生—肿瘤]