| Ye Liuqing,Wang Shi,Wu Zhaoxia,Hong Wensong,Gong Guanzhong,Wu Aiqian,Lian Jinxing,Li Zhen,Deng Li,Wen Ting.Dosimetric effects of field of view on intensity-modulated radiotherapy for breast cancer[J].Chinese Journal of Radiological Medicine and Protection,2023,43(12):1027-1033 |
| Dosimetric effects of field of view on intensity-modulated radiotherapy for breast cancer |
| Received:April 20, 2023 |
| DOI：10.3760/cma.j.cn112271-20230420-00127 |
| KeyWords:Breast cancer Field of view CT value Automatic segmentation Dosimetry |
| FundProject: |
| Author Name | Affiliation | E-mail | | Ye Liuqing | Department of Radiation Oncology, Guangdong Second Provincial General Hospital, Guangzhou 510317, China | | | Wang Shi | Department of Engineering Physics, Tsinghua University, Beijing 518000, China | | | Wu Zhaoxia | Department of Engineering Physics, Tsinghua University, Beijing 518000, China | | | Hong Wensong | Department of Radiation Oncology, Guangdong Second Provincial General Hospital, Guangzhou 510317, China | | | Gong Guanzhong | Department of Radiation Physics, Shandong Cancer Hospital, Jinan 250117, China | | | Wu Aiqian | Department of Radiation Oncology, First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, China | | | Lian Jinxing | Department of Radiation Oncology, First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, China | | | Li Zhen | Department of Radiation Oncology, Guangdong Second Provincial General Hospital, Guangzhou 510317, China | | | Deng Li | Department of Radiation Oncology, Guangdong Second Provincial General Hospital, Guangzhou 510317, China | | | Wen Ting | Department of Radiation Oncology, First Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510405, China | 249715052@qq.com |
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| Abstract:: |
| Objective To investigate the effects of CT images reconstructed using different field of view (FOV) sizes on the automatic segmentation of organs at risk and dose calculation accuracy in radiotherapy after radical mastectomy.Methods Under the same scanning conditions, CT values-electron density conversion curves were established by reconstructing the original CT images of a phantom placed at the isocenter and extended FOV (eFOV) positions using FOV sizes of 50, 60, 70 and 80 cm. Then, these curves were compared. A standard phantom with a known volume was scanned, and the automatic segmentation result of the phantom on CT images reconstructed using different FOV sizes was compared. A total of 30 patients in Guangdong Second Provincial General Hospital from January 2020 to June 2022 with breast cancer were randomly selected. Through simulated positioning, their CT images were reconstructed using different FOV sizes for the purpose of automatic segmentation of organs at risk, followed by comparison between the outcomes of automatic segmentation and physicians'segmentation. The treatment plan established based on CT images reconstructed using a FOV size of 50 cm (FOV50 images for short) was applied to CT images reconstructed using FOV sizes of 60, 70 and 80 cm (FOV60, FOV70 and FOV80 images for short) for dose calculation, and the dose calculation result were compared.Results The CT values - electron density conversion curves derived from CT images reconstructed using different FOV sizes were roughly consistent. At the isocenter, the difference between the segmented volume and actual volume of the standard phantom increased up to a maximum of 6 cm3 (4.8%) with an increase in the FOV size. As indicated by the automatic segmentation result, the segmentation accuracy of the spinal cord, trachea, esophagus, thyroid, healthy mammary gland, and skin decreased with an increase in the FOV size (t = -28.43-8.23, P ＜ 0.05). The comparison of dose calculated based on CT images reconstructed using different FOV sizes showed that there was no statistically significant differences(P>0.05) in the dose to target volume (V95) and the maximum and average doses in the supraclavicular lymph node region, as well as the dose to organs at risk. The coverage for planned target volume decreased with an increase in the FOV size, with a maximum difference of 4.06%.Conclusions It is recommended that, for radiotherapy after radical mastectomy, FOV50 images should be selected for the automatic segmentation of organs at risk, CT-values-electron density conversion curves should be established based on the electron density phantom images of the eFOV region, and the eFOV80 images should be preferred for dose calculation. |
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