title: Calculation of relative biological effectiveness of a low-energy electronic brachytherapy source.
abstract: Low-energy x-rays are known to have a higher relative biological effectiveness (RBE) than higher energy photons such as the gamma rays from 192Ir and 60Co. In this work the initial yield of single- and double-strand DNA breaks (SSB and DSB) and the RBE was estimated for a novel electronic brachytherapy source (EBS), emitting 40-50 kVp photons. An EGSnrc Monte Carlo model of the source was used in combination with the 'Monte Carlo damage simulation' program (Semenenko and Stewart 2004 Radiat. Res. 161 451-57; 2006 Phys. Med. Biol. 51 1693-706). The results indicate a substantially reduced SSB yield and increased DSB yield for the EBS compared to 60Co or 192Ir, leading to an enhanced RBE by 40-50%. The RBE estimate for the low-energy x-ray EBS was found to be very similar to the low-energy gamma ray brachytherapy isotope 125I. Biological damage was estimated in several human tissues: muscle, breast, calcified breast and cortical bone. SSB and DSB yields were similar in all media, except in bone. These findings should be taken into account if the EBS is intended to replace brachytherapy with the commonly used 192Ir isotope.
authors.affiliation: Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Québec, H3G 1A4, Canada.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Reniers
authors.forename: Derek
authors.initials: D
authors.lastname: Liu
authors.forename: Thomas
authors.initials: T
authors.lastname: Rusch
authors.forename: Frank
authors.initials: F
authors.lastname: Verhaegen
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D003037:Cobalt Radioisotopes / Q000737:chemistry; D003198:Computer Simulation; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004583:Electrons; D005720:Gamma Rays; D006801:Humans; D007496:Iridium Radioisotopes / Q000737:chemistry; D007554:Isotopes; D009010:Monte Carlo Method; D017785:Photons; D012062:Relative Biological Effectiveness; D014018:Tissue Distribution; D014965:X-Rays
chemical_list: D003037:Cobalt Radioisotopes; D007496:Iridium Radioisotopes; D007554:Isotopes