Preliminary study on small-field dose measurement using pinpoint ionization chamber in dosimetric end to end audit of IMRT(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2021年第12期
- Page:
- 1502-1507
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Preliminary study on small-field dose measurement using pinpoint ionization chamber in dosimetric end to end audit of IMRT
- Author(s):
- XUE Xian1; HE Zhijian1; YUAN Jilong1; WANG Jin2; YANG Chunyong2; ZHOU Wenshan3; HU Chuanpeng4; CAO Xingjiang2; SUN Gangtao3; JIA Chenzhi4
- 1. National Institute for Radiological Protection, China Centre for Disease Control and Prevention, Beijing 100088, China 2. Jiangsu Provincial Center for Disease Control and Prevention, Nanjing 210009, China 3. Hubei Provincial Center for Disease Control and Prevention, Wuhan 430079, China 4. Henan Institute for Occupational Health, Zhengzhou 450052, China
- Keywords:
- Keywords: pinpoint ionization chamber small-field dose intensity-modulated radiotherapy quality control
- PACS:
- R318；R811.1
- DOI:
- DOI:10.3969/j.issn.1005-202X.2021.12.009
- Abstract:
- Abstract: Objective To discuss the feasibility of using pinpoint ionization chamber for small-field absolute dose measurement in dosimetric end to end audit of IMRT. Methods The study involved 20 hospitals in 3 provinces. The CT scan of IAEA phantom placed with films and TLD which was 7.5 cm from the surface of phantom was transferred into treatment planning system for treatment planning. Seven-field isocenter IMRT in which the multileaf collimator (MLC) radiation field was larger than 2 cm×2 cm and smaller than 4 cm×4 cm was carried out. Meanwhile, pinpoint ionization chamber (0.015 cc) was placed in the solid water phantom where was 7.5 cm from the surface of the phantom for the absolute dose verification of point dose, including (1) dose verification when the treatment plan was translated to solid water phantom at field angles of 0° (2) absolute dose verification when the treatment plan was translated to solid water phantom at actual treatment angles. Results For solid water phantom receiving IMRT MLC small-field radiation, the comparison between absolute dose measured by pinpoint ionization chamber and that calculated by treatment planning system showed that the deviation was less than 5% when the 7-field radiation angles returned to 0°, and that it was also less than 5 % for actual treatment angles. After verification, the 7-field IMRT was performed on IAEA phantom, obtaining a TLD deviation less than 7% and ≥90% absolute dose passing rate (3%, 3 mm gamma criterion) for Gafchromic EBT3 film (high-dose planning target volume) in the phantom, which satisfied IAEA standard. Conclusion Pinpoint ionization chamber can be used for absolute dose verification for IMRT MLC small-field radiation.
Last Update: 2021-12-24