Effect of different cone-beam CT image-guidance strategies on the accumulated dose of radiotherapy for spine metastases
Jia Chenghao1, Zhao Bo2,3, Gao Xianshu1, Zhang Min1, Gao Yan1, Liu Siwei1, Shang Zhaocai1, Li Yue1, Liu Peilin1
1Department of Radiation Oncology, Peking University First Hospital, Beijing 100034, China; 2Department of Engineering Physics, Tsinghua University, Beijing 100084, China; 3Key Laboratory of Particle & Radiation Imaging, Ministry of Education, Tsinghua University, Beijing 100084, China
Abstract：Objective To evaluate the effect of setup errors from daily cone-beam computed tomography (CBCT) on the accumulated dose under different image-guidance (IG) strategies, aiming to investigate the appropriate IG strategies during radiotherapy for the spine metastases. Methods A total of 720 CBCT scans of 36 vertebral lesions were obtained. All 36 lesions were divided into the simultaneous boosting (PTV 40Gy/20f, GTV 60Gy/20f, n=20) and conventional radiotherapy groups (PTV 40Gy/20f, n=16). The actual fractionated plan was recalculated simulatively after transferring the isocenter of the initial plan according to the interfraction setup error. Under no daily image-guidance (no-DIG) strategies including twice imaging guidance weekly (TIG), initial 5 days then weekly imaging guidance (5D+WIG), WIG and no imaging guidance (NIG), the dose deviation was calculated between the delivered dose accumulated by each actual fractionated plan and the dose distribution under DIG. The tolerance of dose deviation for the target was within ±5% and the Dmax of the spinal cord was limited below 45Gy. Results Under different image-guidance strategies of TIG, 5D+WIG, WIG and NIG, the median dose deviation was approximately ±1% for the CTV D95% and Dmax of spinal cord. However, the median dose deviation wasbeyond-5% for the PTV D95% when conventional radiotherapy was given. The median dose deviation was approximately 10% for the Dmax of spinal cord and the proportion of cases whose maximum irradiated dose of spinal cord was more than 4500 cGy was ≥70%. Also, the median dose deviation was beyond -5% for the GTV D95% and PTV D95% when simultaneous boosting was delivered. Conclusions Because the dose deviation of CTVand spinal cord is within the tolerance limit, the image-guidance strategies could be chosen according to the clinical practice when conventional radiotherapy is delivered. However, the dose deviation of spinal cord, GTV and PTV exceeds the tolerance limit under no-DIG strategieswhen simultaneous boosting is delivered. Hence, it is necessary to perform daily IGRT for the spine metastases.
Jia Chenghao,Zhao Bo,Gao Xianshu et al. Effect of different cone-beam CT image-guidance strategies on the accumulated dose of radiotherapy for spine metastases[J]. Chinese Journal of Radiation Oncology, 2021, 30(5): 475-480.
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