title: Positional Accuracy of Treating Multiple Versus Single Vertebral Metastases With Stereotactic Body Radiotherapy.
abstract: The aim of this study is to determine whether stereotactic body radiotherapy for multiple vertebral metastases treated with a single isocenter results in greater intrafraction errors than stereotactic body radiotherapy for single vertebral metastases and to determine whether the currently used spinal cord planning organ at risk volume and planning target volume margins are appropriate. Intrafraction errors were assessed for 65 stereotactic body radiotherapy treatments for vertebral metastases. Cone beam computed tomography images were acquired before, during, and after treatment for each fraction. Residual translational and rotational errors in patient positioning were recorded and planning organ at risk volume and planning target volume margins were calculated in each direction using this information. The mean translational residual errors were smaller for single (0.4 (0.4) mm) than for multiple vertebral metastases (0.5 (0.7) mm; P = .0019). The mean rotational residual errors were similar for single (0.3° (0.3°) and multiple vertebral metastases (0.3° (0.3°); P = .862). The maximum calculated planning organ at risk volume margin in any direction was 0.83 mm for single and 1.22 for multiple vertebral metastases. The maximum calculated planning target volume margin in any direction was 1.4 mm for single and 1.9 mm for multiple vertebral metastases. Intrafraction errors were small for both single and multiple vertebral metastases, indicating that our strategy for patient immobilization and repositioning is robust. Calculated planning organ at risk volume and planning target volume margins were smaller than our clinically employed margins, indicating that our clinical margins are appropriate.
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Joe H
authors.initials: JH
authors.lastname: Chang
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Arnjeet
authors.initials: A
authors.lastname: Sangha
authors.affiliation: 2 Department of Medical Physics, BC Cancer Agency, Sindi Ahluwalia Hawkins Centre for the Southern Interior, Kelowna, BC, Canada.
authors.forename: Derek
authors.initials: D
authors.lastname: Hyde
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Hany
authors.initials: H
authors.lastname: Soliman
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Sten
authors.initials: S
authors.lastname: Myrehaug
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Ruschin
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Young
authors.initials: Y
authors.lastname: Lee
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
authors.affiliation: 1 Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada.
authors.forename: Renee
authors.initials: R
authors.lastname: Korol
mesh_terms: D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D006801:Humans; D008279:Magnetic Resonance Imaging; D056888:Patient Positioning; D016634:Radiosurgery / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D061089:Radiotherapy, Image-Guided; D012189:Retrospective Studies; D013125:Spinal Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000556:secondary*; D047368:Tumor Burden
keywords: cone beam computed tomography; image guided; intensity modulated; radiosurgery; radiotherapy; spine