Comparison of dosimetric impacts of MLC systematic errors on VMAT and IMRT plans for nasopharyngeal carcinoma(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2019年第10期
- Page:
- 1139-1144
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Comparison of dosimetric impacts of MLC systematic errors on VMAT and IMRT plans for nasopharyngeal carcinoma
- Author(s):
- YE Shumin; TENG Jianjian; SHI Jinping; ZHANG Liwen; LIU Zhibin
- Department of Radiation Oncology, Cancer Center, First People’s Hospital of Foshan/Affiliated Foshan Hospital of Sun Yat-sen University, Foshan 528000, China
- Keywords:
- ; Keywords: nasopharyngeal carcinoma; multi-leaf collimator; systematic error; intensity-modulated radiotherapy; volumetric modulated arc therapy; dosimetry
- PACS:
- R815.6
- DOI:
- DOI:10.3969/j.issn.1005-202X.2019.10.005
- Abstract:
- Abstract: Objective To study the differences in the dosimetric impacts of multi-leaf collimator (MLC) systematic errors on volumetric modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) plans for nasopharyngeal carcinoma. Methods Twenty patients with nasopharyngeal carcinoma were randomly enrolled in the study. Two different plans, namely VMAT and IMRT, were designed for each patient. The systematic errors of 0.2, 0.5, 1.0 mm were manually generated by only changing the positions of MLC leaves in the treatment plan file via MATLAB 2009a. The dose was recomputed after the modified plan file was inputted to treatment planning system. The impacts of MLC systematic errors on generalized equivalent uniform dose (gEUD) of planning target volume (PTV) and organ-at-risk between two plans were compared, and the relationship between gEUD difference and MLC systematic errors was analyzed. Results There were statistical differences in the gEUD variations of PTV and organs-at-risk between two plans (P<0.001). The gEUD variations of PGTV, PTVnd, PTV1, PTV2, brainstem, spinal cord, left parotid gland and right parotid gland varied linearly with MLC systematic errors. The corresponding gEUD variations due to MLC systematic errors in VMAT plan were 3.6, 3.8, 4.0, 3.0, 5.6, 5.6, 6.8 and 6.8 %/mm, respectively (P<0.001), which were less than 10.7, 10.5, 11.2, 10.7, 16.6, 15.0, 14.6 and 14.4 %/mm in IMRT plan (P<0.001). Conclusion MLC systematic error has a greater dosimetric impact on IMRT plan than VMAT plan. The MLC system errors in VMAT and IMRT should be less than 0.6 and 0.2 mm, respectively, so as to ensure that the gEUD variation of PGTV is controlled within 2%.
Last Update: 2019-10-29