Dosimetric effects of systematic setup errors on hippocampus sparing prophylactic cranial irradiation(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2021年第8期
- Page:
- 930-934
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Dosimetric effects of systematic setup errors on hippocampus sparing prophylactic cranial irradiation
- Author(s):
- WANG Pan; CHEN Junjie; ZHAO Ting; YANG Wanfu; KONG Wei; YE Hongqiang; SHANG Jun
- Department of Radiotherapy, Cancer Hospital, General Hospital of Ningxia Medical University, Yinchuan 750004, China
- Keywords:
- Keywords: hippocampus prophylactic cranial irradiation systematic setup error dose distribution
- PACS:
- R815.6
- DOI:
- DOI:10.3969/j.issn.1005-202X.2021.08.002
- Abstract:
- Abstract: Objective To investigate the effects of different systematic setup errors on the dose distribution in hippocampus sparing prophylactic cranial irradiation for lung cancer. Methods A total of 20 lung cancer patients were randomly selected, and all of them received hippocampus sparing prophylactic cranial irradiation. The systematic setup errors of 1, 3 and 5 mm in three-dimensional 6 directions were simulated by moving the isocenter of the treatment plan in treatment planning system, respectively and then the dose distributions of the generated plans with different systematic setup errors were recalculated without flux calculation. Under different systematic setup errors, the changes of dose distribution in target area and organs-at-risk to systematic setup errors were analyzed, and the sensitivity of dosimetric parameters of target areas and organs-at-risk were discussed. Results The mean dose deviation of CTV D90 did not exceed 2% in the 6 directions with the systematic setup errors of 1, 3 and 5 mm. The significant dose variation of CTV D90 was only found in inferior direction (systematic setup error of 1 mm), in superior and inferior directions (systematic setup error of 3 mm), and in superior, inferior and posterior directions (systematic setup error of 5 mm) (all P<0.05). When the systematic setup error was 1 mm, the mean dose deviation of the hippocampus was greater than 3% in left-right and superior-inferior directions. With the systematic setup error of 3 mm and 5 mm, the mean dose deviation of the hippocampus was more than 10% in the 6 direction. Except for the hippocampus dose deviation in posterior direction under the systematic setup error of 1 mm (P>0.05), the hippocampus dose deviations were statistically significant (P<0.05). When the systematic setup error was 1 mm, the proportions of the dose deviations greater than 5% for hippocampus, left and right eyeballs and left and right lens were 26.19%, 26.20%, 26.19%, 10.71% and 17.86%, respectively. When the systematic setup error was 3 mm, the proportions of the dose deviation greater than 10% for hippocampus, left and right eyeballs, left and right lens and left and right optic nerve was 97.62%, 69.05%, 66.67%, 30.95%, 25.00%, 1.19% and 3.57%, respectively. Both target area and the hippocampus had the highest error sensitivity in superior-inferior direction. Conclusion Systematic setup error has little effect on CTV dose distribution, and the PTV formed by CTV with an expansion of 3 mm is adequate to ensure that the target area receives sufficient prescription dose. Organs-at-risk, especially the hippocampus, eyeball and lens, are particularly sensitive to systematic setup error. The larger the error is, the greater the effect on the dose distribution is. Therefore, in treatment practice, it is necessary to strictly control the setup error, especially the setup error in superior-inferior direction.
Last Update: 2021-07-30