title: Quality of tri-Co-60 MR-IGRT treatment plans in comparison with VMAT treatment plans for spine SABR.
abstract: OBJECTIVE
  To investigate the plan quality of tri-Co-60 intensity-modulated radiation therapy (IMRT) plans for spine stereotactic ablative radiotherapy (SABR).
  
  
  METHODS
  A total of 20 patients with spine metastasis were retrospectively selected. For each patient, a tri-Co-60 IMRT plan and a volumetric-modulated arc therapy (VMAT) plan were generated. The spinal cords were defined based on MR images for the tri-Co-60 IMRT, while isotropic 1-mm margins were added to the spinal cords for the VMAT plans. The VMAT plans were generated with 10-MV flattening filter-free photon beams of TrueBeam STx™(Varian Medical Systems, Palo Alto, CA), while the tri-Co-60 IMRT plans were generated with the ViewRay™system (ViewRay inc., Cleveland, OH). The initial prescription dose was 18 Gy (1 fraction). If the tolerance dose of the spinal cord was not met, the prescription dose was reduced until the spinal cord tolerance dose was satisfied.
  
  
  RESULTS
  The mean dose to the target volumes, conformity index and homogeneity index of the VMAT and tri-Co-60 IMRT were 17.8 ± 0.8 vs 13.7 ± 3.9 Gy, 0.85 ± 0.20 vs 1.58 ± 1.29 and 0.09 ± 0.04 vs 0.24 ± 0.19, respectively. The integral doses and beam-on times were 16,570 ± 1768 vs 22,087 ± 2.986 Gy cm3and 3.95 ± 1.13 vs 48.82 ± 10.44 min, respectively.
  
  
  CONCLUSIONS
  The tri-Co-60 IMRT seems inappropriate for spine SABR compared with VMAT. Advances in knowledge: For spine SABR, the tri-Co-60 IMRT is inappropriate owing to the large penumbra, large leaf width and low dose rate of the ViewRay system.
authors: 1 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.|2 Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea.|3 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.
authors: Chang Heon
authors: CH
authors: Choi
authors: 1 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.|2 Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea.|3 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.
authors: So-Yeon
authors: SY
authors: Park
authors: 1 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.|2 Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea.|3 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.
authors: Jung-In
authors: JI
authors: Kim
authors: 1 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.|2 Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea.|3 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.
authors: Jin Ho
authors: JH
authors: Kim
authors: 4 Department of Radiation Oncology, Ewha Womans University School of Medicine, Seoul, Republic of Korea.
authors: Kyubo
authors: K
authors: Kim
authors: 5 Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Republic of Korea.
authors: Joel
authors: J
authors: Carlson
authors: 1 Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea.|2 Institute of Radiation Medicine, Medical Research Center, Seoul National University, Seoul, Republic of Korea.|3 Biomedical Research Institute, Seoul National University Hospital, Seoul, Republic of Korea.|6 Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Suwon, Republic of Korea.
authors: Jong Min
authors: JM
authors: Park
mesh_terms: D006801:Humans; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D013125:Spinal Neoplasms / Q000532:radiotherapy*; D013131:Spine / Q000528:radiation effects; D016896:Treatment Outcome