Verification of positioning accuracy of MLC leaves of 7 medical linear accelerators in IMRT in Hubei province
10.3760/cma.j.issn.0254-5098.2019.02.009
- VernacularTitle:湖北省7台医用直线加速器调强放射治疗多叶光栅叶片到位精度验证方法研究
- Author:
Wenshan ZHOU
1
;
Jie YU
;
Gangtao SUN
;
Song YE
;
Xinxing MA
Author Information
1. 湖北省疾病预防控制中心放射卫生监测与评价部
- Keywords:
Intensity modulated radiation therapy;
MLC leaves;
Radiochromic film;
Positioning accuracy
- From:
Chinese Journal of Radiological Medicine and Protection
2019;39(2):132-136
- CountryChina
- Language:Chinese
-
Abstract:
Objective To verify the leaf positioning accuracy of multi-leaf collimator (MLC) in intensity modulated radiation therapy (IMRT) by using radiochromic films to provide references for IMRT quality control.Methods Medical linear accelerators of different designs,owned by 7 first-class hospitals at grade-3 in Hubei,were selected for this verification study.Five strip picket fence pattern was created by treatment planning system (TPS).Each strip was 0.6 cm wide with a 3 cm strip separation.MLC leaf positions,positioning bias and opening widths were then measured with EBT2 radiochromic films.Results According to IAEA standards,the film-measured and TPS planned MLC leaf position difference was ±0.5 mm.The difference of MCL strip position of No.5 and No.7 accelerator was 0.7 and-1.0 mm,respectively,not in line with the IAEA standards.The difference of film-measured MLC leaf position between each pairs and all pairs of leaves of 7 accelerators were all within ± 0.5 mm,in line with the IAEA requirements.As required by IAEA,the difference of opening width of MLC leave of each pair relative to the averaged widths of all pairs should be within ±0.75 mm.The filem-measured values from 7 accelerators ranged from-0.6 to 0.5 mm,all in line with the IAEA standards.Standard deviation of opening width of all leaves were required to be within 0.3 mm.The measured values from 7 accelerators ranged from 0.1 to 0.2 mm,in line with the IAEA standard.Conclusions The use of EBT2 radiochromic films to verify MLC leaf positioning accuracy is an important means of quality control owing to its simplicity and high measurement accuracy.It is recommended for verification use at a large scale.
