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Actual measurement verification of dose calculation accuracy based on cone-beam CT images
Chen Li, Zhou Gang, Sun Yanze, Peng Qiliang, Han Jieguan, Tian Ye
Department of Radiotherapy Oncology, the Second Affiliated Hospital of Soochow University, Institute of Radiotherapy Oncology, Soochow University, Suzhou Key Laboratory for Radiation Oncology, Suzhou 215004, China
AbstractObjective To evaluate the dose calculation accuracy of cone-beam CT (CBCT) image by actual measurement method. Methods CBCT images of 60 patients in the Second Affiliated Hospital of Soochow University from September, 2021 to May, 2022 were retrospectively analyzed. CBCT images of full-fan and half-fan scanning of the head, half-fan scanning of the chest and pelvis were obtained by the Varian OBI system. Hounsfield unit - electron density (HU-ED) curves corresponding to the scanning conditions were established with CIRS electron density phantom. The radiotherapy plans were designed on the CBCT images, and the dose calculation results of the detection point were compared with the ionization chamber measurement results to analyze the dose error. Then, three-dimensional dose verification system was adopted to detect the accuracy of the CBCT image radiotherapy plans implementation process in 60 patients, and the accuracy of dose calculation was verified according to the D99%, Dmean, D1% of target volume, Dmean and D1% of organs at risk (OAR), and the γ pass rate. Results In point dose detection in phantom, the dose calculation errors of CBCT images in the above four scanning patterns were -1.06%±0.87%、-1.67%±0.86%, 0.91%±0.73%, -1.54%±0.90%, respectively. In dosimetric verification based on patients' CBCT image treatment plan, the mean difference of Dmean, D99%, and D1% of planning target volume (PTV) in all scanning modes were not higher than 2%, and the Dmean and D1% differences of other OAR were not higher than 3%, except for the lens of patients in the head. The average γ values of target volume and OAR were less than 0.5 under the criteria of 3%/2 mm. Conclusions Under the condition of correctly establishing HU-ED curves, intensity-modulated radiation therapy (IMRT) / volumetric-modulated arc therapy (VMAT) planning based on CBCT images can be employed to estimate and monitor the actual dose to target volume and OAR in adaptive radiotherapy. Full-fan scanning patterns can further improve the accuracy of dose calculation for the head of patients.
Chen Li,Zhou Gang,Sun Yanze et al. Actual measurement verification of dose calculation accuracy based on cone-beam CT images[J]. Chinese Journal of Radiation Oncology, 2023, 32(6): 539-545.
Chen Li,Zhou Gang,Sun Yanze et al. Actual measurement verification of dose calculation accuracy based on cone-beam CT images[J]. Chinese Journal of Radiation Oncology, 2023, 32(6): 539-545.
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