title: Dosimetric characterisation of bismuth shields in CT: measurements and Monte Carlo simulations.
abstract: Although bismuth shields are frequently used in radiology to reduce radiation dose, its mechanism has not been fully investigated. Dosimetric characteristics of bismuth shields in computed tomography (CT) were assessed with ion chamber and Monte Carlo (MC) simulations. Primary attenuation and backscatter effects of paediatric (2-ply) and adult (4-ply) bismuth shields were measured. Simulated CT beams were used for ion chamber measurements. Radiation doses were measured free-in-air and in the tissue-equivalent slabs. MC simulations for the same settings were also performed. Mean dose reductions from primary attenuation were 23% (2-ply) and 40% (4-ply). The dose increase from backscatter was 2% for both shields. MC simulations for primary beam dose reduction were 20% (2-ply) and 38% (4-ply); the backscatter dose increase was around 6% for both shields. In summary, primary attenuation is the major factor that introduces the dose reduction in bismuth and the dose increase from backscatter is negligible.
authors.affiliation: Medical Physics Graduate Program, Department of Radiology, Medical Center, Duke University, Durham, NC 27705, USA.
authors.forename: Sangroh
authors.initials: S
authors.lastname: Kim
authors.forename: Terry T
authors.initials: TT
authors.lastname: Yoshizumi
authors.forename: Donald P
authors.initials: DP
authors.lastname: Frush
authors.forename: Colin
authors.initials: C
authors.lastname: Anderson-Evans
authors.forename: Greta
authors.initials: G
authors.lastname: Toncheva
mesh_terms: D000328:Adult; D001729:Bismuth / Q000737:chemistry*; D001822:Body Burden; D002648:Child; D003198:Computer Simulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008954:Models, Biological; D009010:Monte Carlo Method; D011835:Radiation Protection / Q000295:instrumentation*; D011874:Radiometry / Q000379:methods*; D012542:Scattering, Radiation; D014057:Tomography, X-Ray Computed
chemical_list: D001729:Bismuth