title: Image-guided radiotherapy using megavoltage cone-beam computed tomography for treatment of paraspinous tumors in the presence of orthopedic hardware.
abstract: OBJECTIVE
  This report describes a new image-guided radiotherapy (IGRT) technique using megavoltage cone-beam computed tomography (MV-CBCT) to treat paraspinous tumors in the presence of orthopedic hardware.
  
  
  METHODS
  A patient with a resected paraspinous high-grade sarcoma was treated to 59.4 Gy with an IMRT plan. Daily MV-CBCT imaging was used to ensure accurate positioning. The displacement between MV-CBCT and planning CT images were determined daily and applied remotely to the treatment couch. The dose-volume histograms of the original and a hypothetical IMRT plan (shifted by the average daily setup errors) were compared to estimate the impact on dosimetry.
  
  
  RESULTS
  The mean setup corrections in the lateral, longitudinal, and vertical directions were 3.6 mm (95% CI, 2.6-4.6 mm), 4.1 mm (95% CI, 3.2-5.0 mm), and 1.0 mm (95% CI, 0.6-1.3 mm), respectively. Without corrected positioning, the dose to 0.1 cc of the spinal cord increased by 9.4 Gy, and the doses to 95% of clinical target volumes 1 and 2 were reduced by 4 Gy and 4.8 Gy, respectively.
  
  
  CONCLUSIONS
  Megavoltage-CBCT provides a new alternative image-guided radiotherapy approach for treatment of paraspinous tumors in the presence of orthopedic hardware by providing 3D anatomic information in the treatment position, with clear imaging of metallic objects and without compromising soft-tissue information.
authors.affiliation: Department of Radiation Oncology, University of California San Francisco, San Francisco, CA 94115, USA.
authors.forename: Eric K
authors.initials: EK
authors.lastname: Hansen
authors.forename: David A
authors.initials: DA
authors.lastname: Larson
authors.forename: Michele
authors.initials: M
authors.lastname: Aubin
authors.forename: Josephine
authors.initials: J
authors.lastname: Chen
authors.forename: Martina
authors.initials: M
authors.lastname: Descovich
authors.forename: Amy M
authors.initials: AM
authors.lastname: Gillis
authors.forename: Olivier
authors.initials: O
authors.lastname: Morin
authors.forename: Ping
authors.initials: P
authors.lastname: Xia
authors.forename: Jean
authors.initials: J
authors.lastname: Pouliot
mesh_terms: D005260:Female; D006801:Humans; D007796:Laminectomy; D008875:Middle Aged; D009989:Orthotic Devices; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012509:Sarcoma / Q000532:radiotherapy* / Q000556:secondary / Q000601:surgery; D013117:Spinal Cord Compression / Q000601:surgery; D013125:Spinal Neoplasms / Q000532:radiotherapy* / Q000556:secondary / Q000601:surgery; D013130:Spinal Stenosis / Q000601:surgery; D013904:Thoracic Vertebrae; D014057:Tomography, X-Ray Computed / Q000379:methods