Effects of setup errors in postoperative intensity-modulated radiotherapy of cervical cancer on cumulative target dose deviation(PDF)
《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]
- Issue:
- 2021年第3期
- Page:
- 295-301
- Research Field:
- 医学放射物理
- Publishing date:
Info
- Title:
- Effects of setup errors in postoperative intensity-modulated radiotherapy of cervical cancer on cumulative target dose deviation
- Author(s):
- OUYANG Shuigen; GUO Qing; LIU Tingting; TAO Na; CHENG Jianqiang; AN Yongwei; WEI Xiyi; TAO Fali; NIU Ruijun
- Department of Radiation Oncology, Gansu Provincial Cancer Hospital, Lanzhou 730050, China
- Keywords:
- Keywords: cervical cancer intensity-modulated radiotherapy image guidance setup error dosimetry computer-aided
- PACS:
- R318；R815
- DOI:
- DOI:10.3969/j.issn.1005-202X.2021.03.005
- Abstract:
- Abstract: Objective To obtain the inter-fractional setup errors in postoperative intensity-modulated radiotherapy (IMRT) of cervical cancer by kilovolt cone beam computed tomography (CBCT), and to analyze the variation of cumulative target dose deviation caused by inter-fractional setup errors. Methods A total of 61 patients treated with postoperative IMRT for cervical cancer were enrolled in the study, and their setup errors were obtained by 916 CBCT scans. The setup errors were inputted into treatment planning system, and the cumulative setup error dose was obtained by superposing the inter-fractional setup error doses. The deviation percentage was computed according to deviation formula and the standard planned dose. Results The setup errors in the x, y, z directions and offset isocentric distances were 0.04 (-0.16, 0.25)、-0.05(-0.37, 0.28)、 0.10(-0.06, 0.24), and 0.55 (0.38, 0.78) cm, respectively. Except for the HIsum-HIplan of CTV as well as the Dsum_D50-Dplan_D50 and HIsum-HIplan of CTV1, there were statistical differences in the paired test on the other clinical target areas, and there was statistical significance in the paired test on planning target areas, except for the Dsum_median-Dplan_median, Dsum?mean-Dplan_mean, Dsum_D50-Dplan_D50 of PGTVnd. The comparison of the cumulative setup error dose with the standard planned dose showed a negative skewed distribution, with a decreased kurtosis. The dose deviations of GTVnd, CTV, CTV1, CTVn, CTV_all and PGTVnd, PTV, PTV1, PTVn, PTV_all were all decreased, and the cumulative dose deviations in the planning target areas were significantly larger than those in the clinical target areas. The deviations of Dmin_deviation, D98_ deviation and D95_deviation were the largest, followed by Dmax_deviation, D5_deviation, D2_deviation, while Dmedian_deviation, Dmean_deviation and D50_deviation had the smallest deviations. The reverse S-type DVH curve was skewed to the left, with an increased slope. The HIdeviation of clinical target areas was increased. Conclusion The setup errors in the postoperative IMRT of cervical cancer which has various effects on the cumulative target dose makes the cumulative target dose reduced and the target dose homogeneity worse. Postoperative IMRT for cervical cancer requires CBCT position calibration before each treatment to ensure the accuracy of the dose of each structure in the target area. The risk of additional dose from increasing CBCT frequency should be considered in radiotherapy planning.
Last Update: 2021-03-30