Validation of the effectiveness of leaf position data for the linear accelerator log file
10.3760/cma.j.cn113030-20241121-00444
- VernacularTitle:直线加速器日志文件叶片位置数据的有效性验证
- Author:
Chenlu LIU
1
;
Xiaotong WANG
;
Long SUN
;
Chong XU
;
Bo XUE
;
Xiaohua YANG
;
Guoping SHAN
Author Information
1. 南华大学核科学技术学院，衡阳 421001
- Publication Type:Journal Article
- Keywords:
Radiotherapy;
Electronic portal imaging device;
Multi‐leaf collimator;
Quality assurance;
Log file;
Film
- From:
Chinese Journal of Radiation Oncology
2025;34(8):796-803
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To validate the effectiveness of the leaf position data of multi-leaf collimator (MLC) recorded in the Infinity medical linear accelerator log file (LF).Methods:In this study, the establishment of the film dose calibration curve involved two steps. Initially, the pixel values obtained from scanning the film were converted into net optical density values. Subsequently, a sixth-order polynomial fit was performed on the net optical density and dose data. The picket fence (PF) tests were performed on the electronic portal imaging device (EPID) and film, and the corresponding acquired PF test images were analyzed using the relative leaf travel distance, relative leaf position, relative leaf pair full-width half -maximum (FWHM), and relative leaf pair neighbor region width analysis index, and compared with the relevant results in LF. In addition, to investigate the effect of gravity on the recorded leaf position data by the Infinity medical linear accelerator LF, the above PF tests were executed at 0°, 90°, 180°, and 270° gantry angles, respectively. Intergroup differences were assessed with the Wilcoxon rank-sum test.Results:The film dose calibration curve demonstrated high goodness-of-fit, with a correlation coefficient ( R2) of 0.9994. Across all gantry angles, the dispersion of overall leaf position data for EBT3 film, EPID, and LF followed a consistent pattern based on four analysis metrics: EBT3 film > EPID > LF. Moreover, for each analysis metric, inter-tool differences in standard deviations of results were consistently below 0.1 mm, and this pattern was invariant to gantry angle. Conclusions:The leaf position data recorded in the Infinity medical linear accelerator LF have a high degree of accuracy, and can be used as reference for the actual position of the MLC leaf. Furthermore, gravitational forces exhibit negligible impact on leaf position data acquired via LF.
