Slosarek Krzysztof, Szlag Marta, Bekman Barbara, Grzadziel Aleksandra
Centre of Oncology - Maria Sklodowska Curie, Memorial Institute, Branch Gliwice, Radiotherapy and Brachytherapy Planning Department, Poland.
Rep Pract Oncol Radiother. 2010 Feb 20;15(1):8-14. doi: 10.1016/j.rpor.2010.01.003. eCollection 2010.
The aim of the study was to estimate the dose at the reference point applying an aSi-EPID device in the course of patient treatment.
The method assumes direct proportionality between EPID signal and dose delivered to the patient reference point during the treatment session. The procedure consists of treatment plan calculation for the actual patient in the arc technique. The plan was realized with an elliptic water-equivalent phantom. An ionization chamber inside the phantom measured the dose delivered to the reference point. Simultaneously, the EPID matrix measured the CU distribution. EPID signal was also registered during patient irradiation with the same treatment plan. The formula for in vivo dose calculation was based on the CU(g) function, EPID signal registered during therapy and the relation between the dose and EPID signal level measured for the phantom. In vivo dose was compared with dose planned with the treatment planning system. Irradiation was performed with a Clinac accelerator by Varian Medical Systems in the RapidArc technique. The Clinac was equipped with an EPID matrix (electronic portal image device) of aSi-1000. Treatment plans were calculated with the Eclipse/Helios system. The phantom was a Scanditronix/Wellhöfer Slab phantom, and the ionization chamber was a 0.6 ccm PTW chamber.
In vivo dose calculations were performed for five patients. Planned dose at the reference point was 2 Gy for each treatment plan. Mean in vivo dose was in the range of 1.96-2.09.
Our method was shown to be appropriate for in vivo dose evaluation in the RapidArc technique.
本研究的目的是在患者治疗过程中应用非晶硅电子射野影像装置（aSi-EPID）估计参考点处的剂量。
该方法假定在治疗过程中EPID信号与传递至患者参考点的剂量成正比。该程序包括针对实际患者采用弧形技术进行治疗计划计算。使用椭圆形水等效体模实现该计划。体模内的电离室测量传递至参考点的剂量。同时，EPID矩阵测量剂量计算单元（CU）分布。在使用相同治疗计划对患者进行照射期间也记录EPID信号。体内剂量计算的公式基于CU(g)函数、治疗期间记录的EPID信号以及针对体模测量的剂量与EPID信号水平之间的关系。将体内剂量与治疗计划系统规划的剂量进行比较。使用瓦里安医疗系统公司的Clinac加速器采用快速弧形技术进行照射。Clinac配备了aSi-1000的EPID矩阵（电子射野影像装置）。使用Eclipse/Helios系统计算治疗计划。体模为Scanditronix/Wellhöfer平板体模，电离室为0.6立方厘米的PTW电离室。
对五名患者进行了体内剂量计算。每个治疗计划在参考点的计划剂量为2 Gy。平均体内剂量在1.96 - 2.09范围内。
我们的方法被证明适用于快速弧形技术中的体内剂量评估。
