title: Spectroscopic characterization of a novel electronic brachytherapy system.
abstract: The Axxent developed by Xoft Inc. is a novel electronic brachytherapy system capable of generating x-rays up to 50 keV. These low energy photon-emitting sources merit attention not only because of their ability to vary the dosimetric properties of the radiation, but also because of the radiobiological effects of low energy x-rays. The objective of this study is to characterize the x-ray source and to model it using the Geant4 Monte Carlo code. Spectral and attenuation curve measurements are performed at various peak voltages and angles and the source is characterized in terms of spectrum and half-value layers (HVLs). Also, the effects of source variation and source aging are quantified. Bremsstrahlung splitting, phase-space scoring and particle-tagging features are implemented in the Geant4 code, which is bench-marked against BEAMnrc simulations. HVLs from spectral measurements, attenuation curve measurements and Geant4 simulations mostly agree within uncertainty. However, there are discrepancies between measurements and simulations for photons emitted on the source transverse plane (90 degrees).
authors.affiliation: Medical Physics Unit, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montréal, Québec, H3G 1A4, Canada.
authors.forename: Derek
authors.initials: D
authors.lastname: Liu
authors.forename: Emily
authors.initials: E
authors.lastname: Poon
authors.forename: Magdalena
authors.initials: M
authors.lastname: Bazalova
authors.forename: Brigitte
authors.initials: B
authors.lastname: Reniers
authors.forename: Michael
authors.initials: M
authors.lastname: Evans
authors.forename: Thomas
authors.initials: T
authors.lastname: Rusch
authors.forename: Frank
authors.initials: F
authors.lastname: Verhaegen
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D001918:Brachytherapy / Q000295:instrumentation* / Q000706:statistics & numerical data; D003198:Computer Simulation; D004582:Electronics, Medical / Q000295:instrumentation / Q000706:statistics & numerical data; D006801:Humans; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy; D019047:Phantoms, Imaging; D017785:Photons / Q000627:therapeutic use; D011880:Radiotherapy Planning, Computer-Assisted; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000295:instrumentation* / Q000706:statistics & numerical data; D014965:X-Rays