Abstract:Objective To investigate the influence of carbon fibre materials (treatment couch top and immobilization baseplate) on the results of dose verification by using Varian Portal Dosimetry (PD) system for treatment regimen of nasopharyngeal carcinoma. Methods CT images and structures of a patient with nasopharyngeal carcinoma, which were provided by the 2015 VARIAN Eclipse Treatment Planning Competition, were adopted to design the treatment regimen and to generate corresponding PD dose verification plans. A Varian Clinac IX linac was employed to deliver the verification plans for the following three cases: A. There were no carbon fibre materials between the linac head and the amorphous silicon electronic portal imager of EPID; B. The Varian image-guided radiation therapy (IGRT) carbon fibre couch top was put between the linac head and the portal imager; C. Both the Varian IGRT couch top and the ORFIT AIO carbon fibre immobilization baseplate were put between the linac head the portal imager. The PD software module was used to analyze the two-dimensional dose distributions for each field. Three sets of Gamma pass rate data were acquired, with each set consisting of 18 Gamma pass rate values. Results Statistical analysis was applied to the three sets of Gamma pass rate data. The statistical results of mean ± standard deviation were as follows: Case A (94.31%±1.75%), Case B (94.35% ±1.81%), Case C (91.58% ±2.91%). The results of t test show that, there is no statistical difference between Gamma pass rate data of Case A and Case B(P>0.05), whereas there is a statistical difference between those of Case A and Case C(P=0.001). Conclusion For treatment regimens of nasopharyngeal carcinoma, the carbon fibre couch top has little influence on the PD dose verification. Yet the combination of carbon fibre couch top and baseplate has significant influence on the dose verification, resulting in obvious decrease in Gamma pass rate values and thus worsening of the verification results.
时飞跃a,秦伟a,赵环宇a,林强b,陈锦飞a. 碳纤维材料对鼻咽癌放疗计划剂量验证的影响[J]. 中国医疗设备, 2016, 31(1): 108-109.
SHI Fei-yuea, QIN Weia,ZHAO Huan-yua, LIN Qiangb,CHEN Jin-feia. The Influence of Carbon Fibre Materials on Dose Verification in Radiotherapy Regimen for Nasopharyngeal Carcinoma. China Medical Devices, 2016, 31(1): 108-109.