title: Localization accuracy and immobilization effectiveness of a stereotactic body frame for a variety of treatment sites.
abstract: OBJECTIVE
  The purpose of this study was to analyze the pretreatment setup errors and intrafraction motion using cone beam computed tomography (CBCT) for stereotactic body radiation therapy patients immobilized and localized with a stereotactic body frame for a variety of treatment sites.
  
  
  METHODS
  Localization errors were recorded for patients receiving SBRT for 141 lung, 29 liver, 48 prostate, and 45 spine tumors representing 1005 total localization sessions. All patients were treated in a stereotactic body frame with a large custom-molded vacuum pillow. Patients were first localized to the frame using tattoos placed during simulation. Subsequently, the frame was aligned to the room lasers according to the stereotactic coordinates determined from the treatment plan. Every patient received a pretreatment and an intrafraction CBCT. Abdominal compression was used for all liver patients and for approximately 40% of the lung patients to reduce tumor motion due to respiration.
  
  
  RESULTS
  The mean ± standard deviation pretreatment setup errors from all localizations were -2.44 ± 3.85, 1.31 ± 5.84, and 0.11 ± 3.76 mm in the anteroposterior, superoinferior, and lateral directions, respectively. The mean pretreatment localization results among all treatment sites were not significantly different (F test, P<.05). For all treatment sites, the mean ± standard deviation intrafraction shifts were 0.33 ± 1.34, 0.15 ± 1.45, and -0.02 ± 1.17 mm in the anteroposterior, superoinferior, and lateral directions, respectively. The mean unidimensional intrafraction shifts were statistically different for several of the comparisons (P<.05) as assessed by the Tukey-Kramer test.
  
  
  CONCLUSIONS
  Despite the varied tumor locations, the pretreatment mean localization errors for all sites were found to be consistent among the treatment sites and not significantly different, indicating that the body frame is a suitable immobilization and localization device for a variety of tumor sites. Our pretreatment localization errors and intrafraction shifts compare favorably with those reported in other studies using different types of immobilization devices.
authors.affiliation: Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas. Electronic address: Ryan.Foster@utsouthwestern.edu.
authors.forename: Ryan
authors.initials: R
authors.lastname: Foster
authors.affiliation: Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Meyer
authors.affiliation: Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas.
authors.forename: Puneeth
authors.initials: P
authors.lastname: Iyengar
authors.affiliation: Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas.
authors.forename: David
authors.initials: D
authors.lastname: Pistenmaa
authors.affiliation: Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas.
authors.forename: Robert
authors.initials: R
authors.lastname: Timmerman
authors.affiliation: Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, Texas.
authors.forename: Hak
authors.initials: H
authors.lastname: Choy
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Timothy
authors.initials: T
authors.lastname: Solberg
mesh_terms: D000005:Abdomen; D054893:Cone-Beam Computed Tomography; D003250:Constriction; D019583:Dose Fractionation, Radiation; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D007103:Immobilization / Q000295:instrumentation*; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D009068:Movement; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*; D016634:Radiosurgery / Q000295:instrumentation*; D061106:Radiotherapy Setup Errors / Q000517:prevention & control / Q000706:statistics & numerical data*; D012119:Respiration; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000601:surgery*