Abstract:Objective To explore the improvement of NCC/T-RT 001-2019 Guidelines of Quality Control of Medical Linear
Accelerators on the analysis of dynamic logs file of light distance scale and multi-leaf collimator (MLC) , and the test method of
gantry-collimator-couch concentricity, in order to obtain more reliable results. Methods Measuring the couch sag with micrometer
for 1/100 mm precision. Using software named Argus (with the beam-hold records filtering function) and Dynalogs Viewer (no data
filtering option) to export the root mean square value (RMS) of MLC leaf error from the MLC log file for Step & Shoot and Sliding
Windows fields and compare them with the evaluation of dose image. The Winston Lutz test was performed by using electronic portal
imaging device (EPID) instead of film to acquire the Winston-Lutz images. Then, the effects of collimator square field and SRS cone
images on the results were compared. Results 1.42 mm couch sag was confirmed due to the 20cm solid water phantom which was
about 70% of the tolerance. Different RMS of leaf error were conducted from Argus and Dynalogs Viewer with Step & Shoot fields.
When comparing them to the g evaluation of dose image, the P values were 0.66 and 0.67 which mean no correlation between the g
evaluation and RMS statistics from both software. In Winston-Lutz testing, the maximum/mean deviations were 1.29/0.93 mm and
0.62/0.37 mm respectively from collimator square field and SRS cone circular field, the latter was about the half of the former which
was at the tolerance limit of linear accelerators for SRS/SBRT purpose. Conclusion The extra uncertainties may be introduced by the
testing defined by the guidelines. This paper introduces some methods for taking account of the issues for matching the tolerances. It
is also suggested in this paper that the revision of the national guidelines of quality control might focus on the testing principles and
setting of the tolerances, but can we leave some flexibilities to local quality control team to decide their own testing procedures based
on their equipment configuration.
顾香莲, 顾煜恺, 龚卿. 基于NCC/T-RT 001-2019质控指南进行医用加速器质控的研究[J]. 中国医疗设备, 2021, 36(7): 68-72.
GU Xianglian, GU Yukai, GONG Qing. Research on Quality Control of Medical Accelerator Based on the NCC/T-RT 001-2019 Guidelines. China Medical Devices, 2021, 36(7): 68-72.