Yuliang Huang1, Chenguang Li1, Haiyang Wang1, Qiaoqiao Hu1, Ruoxi Wang1, Cheng Chang1, Wenjun Ma2, Weibo Li3, Hao Wu4, Yibao Zhang5. 1. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China. 2. State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China. 3. Institute of Radiation Medicine, Helmholtz Zentrum München - German Research Center for Environmental Health (GmbH), Ingolstädter Landstr, 85764 Neuherberg, Germany. 4. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China; Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China. Electronic address: 13552661030@139.com. 5. Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing 100142, China; Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China. Electronic address: zhangyibao@pku.edu.cn.
Abstract
BACKGROUND AND PURPOSE: To evaluate the impact of deformation magnitude and image modality on deformable-image-registration (DIR) accuracy using Halcyon megavoltage cone beam CT images (MVCBCT). MATERIALS AND METHODS: Planning CT images of an anthropomorphic Head phantom were aligned rigidly with MVCBCT and re-sampled to achieve the same resolution, denoted as pCT. MVCBCT was warped with twenty simulated pre-known virtual deformation fields (Ti, i = 1-20) with increasing deformation magnitudes, yielding warped CBCT (wCBCT). The pCT and MVCBCT were registered to wCBCT respectively (Multi-modality and Uni-modality DIR), generating deformation vector fields Vi and Vi' (i = 1-20). Vi and Vi' were compared with Ti respectively to assess the DIR accuracy geometrically. In addition, Vi, Ti, and Vi' were applied to pCT, generating deformed CT (dCTi), ground-truth CT (Gi) and deformed CT' (dCTi') respectively. The Hounsfield Unit (HU) on these virtual CT images were also compared. RESULTS: The mean errors of vector displacement increased with the deformation magnitude. For deformation magnitudes between 2.82 mm and 7.71 mm, the errors of uni-modality DIR were 1.16 mm ~ 1.73 mm smaller than that of multi-modality (p = 0.0001, Wilcoxon signed rank test). DIR could reduce the maximum signed and absolute HU deviations from 70.8 HU to 11.4 HU and 208 HU to 46.2 HU respectively. CONCLUSIONS: As deformation magnitude increases, DIR accuracy continues to deteriorate and uni-modality DIR consistently outperformed multi-modality DIR. DIR-based adaptive radiotherapy utilizing the noisy MVCBCT images is only conditionally applicable with caution.
BACKGROUND AND PURPOSE: To evaluate the impact of deformation magnitude and image modality on deformable-image-registration (DIR) accuracy using Halcyon megavoltage cone beam CT images (MVCBCT). MATERIALS AND METHODS: Planning CT images of an anthropomorphic Head phantom were aligned rigidly with MVCBCT and re-sampled to achieve the same resolution, denoted as pCT. MVCBCT was warped with twenty simulated pre-known virtual deformation fields (Ti, i = 1-20) with increasing deformation magnitudes, yielding warped CBCT (wCBCT). The pCT and MVCBCT were registered to wCBCT respectively (Multi-modality and Uni-modality DIR), generating deformation vector fields Vi and Vi' (i = 1-20). Vi and Vi' were compared with Ti respectively to assess the DIR accuracy geometrically. In addition, Vi, Ti, and Vi' were applied to pCT, generating deformed CT (dCTi), ground-truth CT (Gi) and deformed CT' (dCTi') respectively. The Hounsfield Unit (HU) on these virtual CT images were also compared. RESULTS: The mean errors of vector displacement increased with the deformation magnitude. For deformation magnitudes between 2.82 mm and 7.71 mm, the errors of uni-modality DIR were 1.16 mm ~ 1.73 mm smaller than that of multi-modality (p = 0.0001, Wilcoxon signed rank test). DIR could reduce the maximum signed and absolute HU deviations from 70.8 HU to 11.4 HU and 208 HU to 46.2 HU respectively. CONCLUSIONS: As deformation magnitude increases, DIR accuracy continues to deteriorate and uni-modality DIR consistently outperformed multi-modality DIR. DIR-based adaptive radiotherapy utilizing the noisy MVCBCT images is only conditionally applicable with caution.