title: An effective calibration technique for radiochromic films using a single-shot dose distribution in Gamma Knife(®).
abstract: OBJECTIVE
  A method of calibrating radiochromic films for Gamma Knife(®) (GK) dosimetry was developed. The applicability and accuracy of the new method were examined.
  
  
  METHODS
  The dose distribution for a sixteen millimeter single-shot from a GK was built using a reference film that was calibrated using the conventional multi-film calibration (MFC) method. Another film, the test film, from a different set of films was irradiated under the same conditions as the reference film. The calibration curve for the second set of films was obtained by assigning the dose distribution of the reference film to the optical density of the test film, point by point. To assess the accuracy of this single-film calibration (SFC) method, differences between gamma index pass rates (GIPRs) were calculated.
  
  
  RESULTS
  The SFC curves were successfully obtained with estimated errors of 1.46%. GIPRs obtained with the SFC method for films irradiated using a single-shot showed differences less than one percentage point when dose difference criterion (ΔD) was 2% and the distance to agreement criterion (Δd) was 1 mm. The GIPRs of the SFC method when the films were irradiated following a virtual target treatment plan were consistent with the GIPRs of the MFC method, with differences of less than 0.2 percentage points for ΔD = 1% and Δd = 1 mm.
  
  
  CONCLUSIONS
  The accuracy of the SFC method is comparable to that of conventional multi-film calibration method for GK film dosimetry.
authors.affiliation: Department of Medical Physics, Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejon 34113, Republic of Korea; Center for Ionizing Radiation, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Yuseong-Gu, Daejon 34113, Republic of Korea.
authors.forename: Jae Pil
authors.initials: JP
authors.lastname: Chung
authors.affiliation: Department of Medical Physics, Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejon 34113, Republic of Korea; Center for Ionizing Radiation, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Yuseong-Gu, Daejon 34113, Republic of Korea.
authors.forename: Se Woon
authors.initials: SW
authors.lastname: Oh
authors.affiliation: Center for Ionizing Radiation, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Yuseong-Gu, Daejon 34113, Republic of Korea.
authors.forename: Young Min
authors.initials: YM
authors.lastname: Seong
authors.affiliation: Department of Medical Physics, Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejon 34113, Republic of Korea; Center for Ionizing Radiation, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science, 267 Gajeong-ro, Yuseong-Gu, Daejon 34113, Republic of Korea. Electronic address: chunkj@kriss.re.kr.
authors.forename: Kook Jin
authors.initials: KJ
authors.lastname: Chun
authors.affiliation: Department of Neurosurgery, Seoul National University College of Medicine, 101 Daehang-no Jongno-gu, Seoul 03080, Republic of Korea. Electronic address: htchung@snu.ac.kr.
authors.forename: Hyun-Tai
authors.initials: HT
authors.lastname: Chung
mesh_terms: D002138:Calibration; D005373:Film Dosimetry / Q000379:methods*; D011829:Radiation Dosage; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D035501:Uncertainty
keywords: Dose calibration; Gamma Knife; Gamma index pass rate; Radiochromic film; Single-shot dose distribution