Multi-leaf collimator positioning accuracy analyzed with two film analysis methods: a preliminary multi-center measurement(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2018年第12期
- Page:
- 1375-1385
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Multi-leaf collimator positioning accuracy analyzed with two film analysis methods: a preliminary multi-center measurement
- Author(s):
- XUE Xian1; ZHAO Hongfeng2; LUO Suming1; HE Zhijian1; YANG Chunyong3; LIU Ran4; CHENG Xiaojun5; SUN Gangtao6; CHENG Jinsheng1
- 1. Key Laboratory of Radiation Protection and Nuclear Emergency, National Institute for Radiological Protection and Nuclear Safety, Chinese Center for Disease Control and Prevention, Beijing 100088, China; 2. Beijing Chaoyang Center for Disease Prevention and Control, Beijing 100013, China; 3. Jiangsu Provincial Center for Disease Control and Prevention, Nanjing 210009, China; 4. Sichuan Center for Disease Control and Prevention, Chengdu 610031, China; 5. Henan Institute for Occupational Medicine, Zhengzhou 450052, China; 6. Hubei Provincial Center for Disease Control and Prevention, Wuhan 430079, China
- Keywords:
- ; Keywords: multi-leaf collimator; positioning accuracy; film analysis; normalization method
- PACS:
- R811.1；R312
- DOI:
- DOI:10.3969/j.issn.1005-202X.2018.12.003
- Abstract:
- Abstract: Objective To assess a picket fence test using two methods of film analysis for verifying the positioning accuracy of multi-leaf collimator (MLC). Methods Among selected 15 hospitals in 4 provinces, 8 of them applied Varian accelerator using MLC (Millenium 120), and the other 7 adopted Elekta accelerator using MLC (MLCi or MLCi2). The film was placed at dmax (1.5 cm underwater) in a solid water phantom of 30 cm×30 cm, with a source axis distance of 100 cm. The film received an irradiation of 6 MV and 250 MU per MLC strip. Five MLC strips were generated on EBT3 film, and the width of each strip was 6 mm. The centers of 5 MLC strips were located at -6, -3, 0, 3 and 6 cm from the center of the middle MLC strip. The irradiated films were scanned with Epson Expression 10000XL scanner, and the dose curve of irradiation field (profile) was analyzed and calculated by Film QATM Pro software. Two normalization methods, namely truncating at the smallest local min and max values and normalizing to 0 and 1 (TLN) and equalizing all local min and max values to 0 and 1 (ELN), were used to analyze the field location and deviation of the center, field width and deviation for comparing the MLC positioning accuracy and multi-center measured results. Results The deviation between measured field positions of 5 strips and planned strip positions in 9 hospitals exceeded ±0.5 mm which was recommended by International Atomic Energy Agency (IAEA). The deviation of the center of each irradiation field was up to standard which is ±0.5 mm recommended by IAEA. The deviation between the width of 5 fence fields and planned width (6 mm) was less than ±1 mm, conforming to IAEA standard. Moreover, the deviation and standard deviation of maximum-minimum widths met IAEA standards (no more than 0.75 mm and 0.30 mm, respectively). Conclusion The MLC positioning accuracy measured by two normalization methods of film analysis is similar. Both TLN and ELN are reliable in the verification of MLC positioning accuracy.
Last Update: 2018-12-24