title: Infrared-guided patient setup for lung cancer patients.
abstract: OBJECTIVE
  To evaluate the utility of an infrared-guided patient setup (iGPS) system to reduce the uncertainties in the setup of lung cancer patients.
  
  
  METHODS
  A total of 15 patients were setup for lung irradiation using skin tattoos and lateral leveling marks. Daily electronic portal device images and iGPS marker locations were acquired and retrospectively reviewed. The iGPS-based shifts were compared with the daily electronic portal device image shifts using both the central axis iGPS marker and all five iGPS markers. For shift calculation using the five markers, rotational misalignment was included. The level of agreement between the iGPS and portal imaging to evaluate the setup was evaluated as the frequency of the shift difference in the range of 0-5 mm, 5-10 mm, and >10 mm.
  
  
  RESULTS
  Data were obtained for 450 treatment sessions for 15 patients. The difference in the isocenter shifts between the weekly vs. daily images was 0-5 mm in 42%, 5-10 mm in 30%, and >10 mm in 10% of the images. The shifts seen using the iGPS data were 0-5 mm in 81%, 5-10 mm in 14%, and >10 mm in 5%. Using only the central axis iGPS marker, the difference between the iGPS and portal images was <5 mm in 77%, 5-10 mm in 16%, and >10 mm in 7% in the left-right direction and 73%, 18%, and 9% in the superoinferior direction, respectively. When all five iGPS markers were used, the disagreements between the iGPS and portal image shifts >10 mm were reduced from 7% to 2% in the left-right direction and 9% to 3% in the superoinferior direction. Larger reductions were also seen (e.g., a reduction from 50% to 0% in 1 patient).
  
  
  CONCLUSIONS
  The daily iGPS-based shifts correlated well with the daily electronic portal device-based shifts. When patient movement has nonlinear rotational components, a combination of surface markers and portal images might be particularly beneficial to improve the setup for lung cancer patients.
authors.affiliation: Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Lyatskaya
authors.forename: Steven
authors.initials: S
authors.lastname: James
authors.forename: Joseph H
authors.initials: JH
authors.lastname: Killoran
authors.forename: Ricardo
authors.initials: R
authors.lastname: Soto
authors.forename: Harvey J
authors.initials: HJ
authors.lastname: Mamon
authors.forename: Lee
authors.initials: L
authors.lastname: Chin
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Allen
mesh_terms: D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D006801:Humans; D007259:Infrared Rays / Q000627:therapeutic use; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000532:radiotherapy*; D009068:Movement; D020266:Radiotherapy, Conformal / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity