title: Unintended attenuation in the Leksell Gamma Knife Perfexion calibration-phantom adaptor and its effect on dose calibration.
abstract: The calibration of Leksell Gamma Knife Perfexion (LGK PFX) is performed using a spherical polystyrene phantom 160 mm in diameter, which is provided by the manufacturer. This is the same phantom that has been used with LGK models U, B, C, and 4C. The polystyrene phantom is held in irradiation position by an aluminum adaptor, which has stainless steel side-fixation screws. The phantom adaptor partially attenuates the beams from sectors 3 and 7 by 3.2% and 4.6%, respectively. This unintended attenuation introduces a systematic error in dose calibration. The overall effect of phantom-adaptor attenuation on output calibration of the LGK PFX unit is to underestimate output by about 1.0%.
authors.affiliation: Department of Radiation Oncology, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15217, USA.
authors.forename: Jagdish P
authors.initials: JP
authors.lastname: Bhatnagar
authors.forename: Josef
authors.initials: J
authors.lastname: Novotny
authors.forename: Mubina A
authors.initials: MA
authors.lastname: Quader
authors.forename: Greg
authors.initials: G
authors.lastname: Bednarz
authors.forename: M Saiful
authors.initials: MS
authors.lastname: Huq
mesh_terms: D000535:Aluminum / Q000737:chemistry; D002138:Calibration; D006801:Humans; D015233:Models, Statistical; D009369:Neoplasms / Q000601:surgery*; D019047:Phantoms, Imaging; D011137:Polystyrenes / Q000737:chemistry; D011874:Radiometry / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation; D013193:Stainless Steel; D013997:Time Factors
chemical_list: D011137:Polystyrenes; D013193:Stainless Steel; D000535:Aluminum