Fushe yanjiu yu fushe gongyi xuebao (Feb 2023)
Study on dose calculation of pelvic tumor radiotherapy planning based on iCBCT images
Abstract
In order to discuss the accuracy of iterative cone-beam computed tomography (iCBCT) image used for pelvic tumor dose calculation, thirty cases were selected from a hospital that use a Halcyon accelerator for radiotherapy. The volumetric modulated arc therapy (VMAT) plan was redesigned using Eclipse 15.6 planning system, and the setup iCBCT image acquired for the first time was registered with the planning CT image (pCT). The VMAT plan (pCT plan) of each case was transplanted to the iCBCT image, and the dose was calculated again based on the CT-relative electron density curve calibrated using the iCBCT image to generate a new treatment plan (iCBCT plan). The dosimetric parameters of the two plans were analyzed using SPSS 26.0 software to perform t-tests. The results of D2, D98, Dmean, conformity index (CI), and homogeneity index (HI) in the planning target volume dosimetry parameters of the iCBCT plan were similar to those of the pCT plan. The average differences were 0.71%, 0.53%, 0.97%, 0.25%, and 0.95%, respectively, with no statistical significance (p>0.05). Among the organs at risk, the average difference of Dmean, D5, V20, V30, and V40 between the left and right femoral head, rectum, and bladder was small, with no statistical significance (p>0.05). The parameter with the largest average difference (1.71%) was Dmean of the bladder. Compared with that of the pCT plan, the gamma pass rate of the iCBCT plan was 1%/1 mm standard (88.1±1.1)% and 2%/2 mm standard (97.8±1.2)%. Compared with the measured values, the mean difference between the isocenter dose of the two plans was 0.98% and 0.81%, respectively, with no statistical significance (p>0.05). The results show that in most pelvic cases, the results of the iCBCT images used for radiotherapy planning dose calculation are accurate and reliable, and the accuracy meets the requirements of clinical application.
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