title: Small field dose measurements using plastic scintillation detector in heterogeneous media.
abstract: OBJECTIVE
  The purpose of this study was to evaluate a plastic scintillation detector for the measurement of small field dosimetry and to verify the accuracy of measured dose in comparison with Monte Carlo calculation in a heterogeneous medium.
  
  
  METHODS
  The study is performed with CyberKnife planning and delivery system. The setup consists of a custom made solid lung phantom with the insert of an Exradin W1 scintillation detector or an Exradin A16 ion chamber. The measurement was done for a series of cone sizes from 5 mm to 60 mm, and the dose was calculated by Monte Carlo algorithm in MultiPlan workstation. The difference between measurement and calculation was reported.
  
  
  RESULTS
  Our preliminary results demonstrated the applicability of plastic scintillation detectors in the measurement of small field dosimetry in a heterogeneous medium. The difference between the calculated and measured output factors was less than 3% for all cone sizes from 60 mm down to 5 mm. Without any corrections, the measured dose from the scintillation detector calibrated to the ion chamber reading was also within 3% of the Monte Carlo calculation in the lung phantom for cone sizes 20 mm or larger.
  
  
  CONCLUSIONS
  Small field dosimetry is particularly relevant to stereotactic radiation treatment. The accuracy of dose calculation for small static beams is critical to dose planning so would potentially affect the treatment outcomes in a heterogeneous medium. Our results have shown good agreement with plastic scintillation detector in both homogeneous and heterogeneous medium.
authors.affiliation: Department of Radiation Oncology, NYU Langone Medical Center, New York, NY, 10016, USA.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Xue
authors.affiliation: Department of Radiation Oncology, Erlanger Health System, Chattanooga, TN, 37403, USA.
authors.forename: Jesse D
authors.initials: JD
authors.lastname: McKay
authors.affiliation: Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University Hospital, Baltimore, MD, 21231, USA.
authors.forename: Jimm
authors.initials: J
authors.lastname: Grimm
authors.affiliation: Department of Radiation Oncology, University Hospitals Cleveland Medical Center, Cleveland, OH, 44106, USA.
authors.forename: Chee-Wai
authors.initials: CW
authors.lastname: Cheng
authors.affiliation: Department of Radiation Oncology, Erlanger Health System, Chattanooga, TN, 37403, USA.
authors.forename: Ronald
authors.initials: R
authors.lastname: Berg
authors.affiliation: Academic Urology/Fox Chase Cancer Center, King of Prussia, PA, 19406, USA.
authors.forename: Shu-Ya Lisa
authors.initials: SL
authors.lastname: Grimm
authors.affiliation: Department of Radiation Oncology, MD Anderson Cancer Center at Cooper, Camden, NJ, 08103, USA.
authors.forename: Qianyi
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Radiation Oncology, Eastern Maine Medical Center, Bangor, ME, 04401, USA.
authors.forename: Gopal
authors.initials: G
authors.lastname: Subedi
authors.affiliation: Department of Radiation Oncology, NYU Langone Medical Center, New York, NY, 10016, USA.
authors.forename: Indra J
authors.initials: IJ
authors.lastname: Das
mesh_terms: D006801:Humans; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D017785:Photons; D010969:Plastics; D011874:Radiometry
chemical_list: D010969:Plastics
keywords: Monte Carlo; heterogeneity corrections; plastic scintillation detectors; small field; stereotactic