title: Evaluation of initial setup accuracy and intrafraction motion for spine stereotactic body radiation therapy using stereotactic body frames.
abstract: OBJECTIVE
  The purposes of this study were (1) to evaluate the initial setup accuracy and intrafraction motion for spine stereotactic body radiation therapy (SBRT) using stereotactic body frames (SBFs) and (2) to validate an in-house-developed SBF using a commercial SBF as a benchmark.
  
  
  METHODS
  Thirty-two spine SBRT patients (34 sites, 118 fractions) were immobilized with the Elekta and in-house (BHS) SBFs. All patients were set up with the Brainlab ExacTrac system, which includes infrared and stereoscopic kilovoltage x-ray-based positioning. Patients were initially positioned in the frame with the use of skin tattoos and then shifted to the treatment isocenter based on infrared markers affixed to the frame with known geometry relative to the isocenter. ExacTrac kV imaging was acquired, and automatic 6D (6 degrees of freedom) bony fusion was performed. The resulting translations and rotations gave the initial setup accuracy. These translations and rotations were corrected for by use of a robotic couch, and verification imaging was acquired that yielded residual setup error. The imaging/fusion process was repeated multiple times during treatment to provide intrafraction motion data.
  
  
  RESULTS
  The BHS SBF had greater initial setup errors (mean±SD): -3.9±5.5mm (0.2±0.9°), -1.6±6.0mm (0.5±1.4°), and 0.0±5.3mm (0.8±1.0°), respectively, in the vertical (VRT), longitudinal (LNG), and lateral (LAT) directions. The corresponding values were 0.6±2.7mm (0.2±0.6°), 0.9±5.3mm (-0.2±0.9°), and -0.9±3.0mm (0.3±0.9°) for the Elekta SBF. The residual setup errors were essentially the same for both frames and were -0.1±0.4mm (0.1±0.5°), -0.2±0.4mm (0.0±0.4°), and 0.0±0.4mm (0.0±0.4°), respectively, in VRT, LNG, and LAT. The intrafraction shifts in VRT, LNG, and LAT were 0.0±0.4mm (0.0±0.3°), 0.0±0.5mm (0.0±0.4°), and 0.0±0.4mm (0.0±0.3°), with no significant difference observed between the 2 frames.
  
  
  CONCLUSIONS
  These results showed that the combination of the ExacTrac system with either SBF was highly effective in achieving both setup accuracy and intrafraction stability, which were on par with that of mask-based cranial radiosurgery.
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Han
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: John C
authors.initials: JC
authors.lastname: Bondeson
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: John H
authors.initials: JH
authors.lastname: Lewis
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: Edward G
authors.initials: EG
authors.lastname: Mannarino
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Friesen
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Wagar
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: Tracy A
authors.initials: TA
authors.lastname: Balboni
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Alexander
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.
authors.forename: Nils D
authors.initials: ND
authors.lastname: Arvold
authors.affiliation: Department of Radiation Oncology, Rush University Medical Center, Chicago, Illinois.
authors.forename: David J
authors.initials: DJ
authors.lastname: Sher
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts. Electronic address: fhacker@lroc.harvard.edu.
authors.forename: Fred L
authors.initials: FL
authors.lastname: Hacker
mesh_terms: D054893:Cone-Beam Computed Tomography; D006801:Humans; D007103:Immobilization; D009068:Movement / Q000502:physiology*; D058958:Organs at Risk / Q000528:radiation effects; D011379:Prognosis; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061106:Radiotherapy Setup Errors / Q000517:prevention & control*; D061089:Radiotherapy, Image-Guided; D050397:Radiotherapy, Intensity-Modulated; D013125:Spinal Neoplasms / Q000601:surgery*