Effects of beam uniformity changes of Machine Performance Check on Portal Dosimetry plan dose verification(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2022年第4期
- Page:
- 397-403
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Effects of beam uniformity changes of Machine Performance Check on Portal Dosimetry plan dose verification
- Author(s):
- YAO Kaining; WANG Ruoxi; WU Hao; GONG Jian; LIU Zhuolun; ZHANG Jian; FENG Zhongsu; DU Yi
- Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiotherapy, Peking University Cancer Hospital & Institute, Beijing 100142, China
- Keywords:
- Keywords: plan dose verification beam uniformity Machine Performance Check electronic portal image device Portal Dosimetry
- PACS:
- R811
- DOI:
- DOI:10.3969/j.issn.1005-202X.2022.04.001
- Abstract:
- Abstract: Objective To explore the effects of beam uniformity changes of Machine Performance Check (MPC) on Portal Dosimetry (PD) plan verification, thereby providing references for the threshold setting of MPC uniformity and the calibration frequency of electronic portal imaging device (EPID). Methods Twenty-six patients treated on the EDGE accelerator for the first time, and a case of 10 cm×10 cm square field were selected to make treatment and verification plans. With the increasing deviation of MPC beam uniformity, verification plans were executed before and after EPID calibration. The image dose and gamma passing rate were analyzed and compared in PD module. The MPC beam uniformity of the EDGE accelerator in one year was also listed. Results MPC statistical results for one year showed that beam uniformity deviation had a clear upward trend and the speed was accelerating, which indicated that there was equipment aging in EPID. The comparison of image doses and gamma passing rates of verification plans before and after EPID calibration revealed that the dose difference near the center of image plate was from 1% to 2% for the square field plans of different energies. Due to the increased complexity of the clinical plans, the maximum dose difference reached 10%. Gamma passing rate after EPID calibration was higher than that before calibration. Conclusion Uniformity change of EPID detector has a certain effect on PD plan dose verification, which suggests that when the clinical MPC uniformity threshold is 2%, it can play an early warning role for plan dose verification. EPID should be calibrated before the MPC baseline is re-acquired, thereby ensuring the quality of verification plans and guaranteeing the safety of radiotherapy.
Last Update: 2022-04-27