Assessment of Patient Dose Reduction by Bismuth Shielding in CT Using Measurements, GEANT4 and MCNPX Simulations

Mendes, M; Costa, F; Figueira, C; Madeira, P; Teles, P; Vaz, P

http://hdl.handle.net/10400.17/3011

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Abstract(s)

This work reports on the use of two different Monte Carlo codes (GEANT4 and MCNPX) for assessing the dose reduction using bismuth shields in computer tomography (CT) procedures in order to protect radiosensitive organs such as eye lens, thyroid and breast. Measurements were performed using head and body PMMA phantoms and an ionisation chamber placed in five different positions of the phantom. Simulations were performed to estimate Computed Tomography Dose Index values using GEANT4 and MCNPX. The relative differences between measurements and simulations were <10 %. The dose reduction arising from the use of bismuth shielding ranges from 2 to 45 %, depending on the position of the bismuth shield. The percentage of dose reduction was more significant for the area covered by the bismuth shielding (36 % for eye lens, 39 % for thyroid and 45 % for breast shields).

Keywords

Algorithms Breast Computer Simulation Computers Equipment Design Female Humans Lens, Crystalline Monte Carlo Method Phantoms, Imaging Protective Devices Radiation Dosage Radiation Protection Reproducibility of Results Thyroid Gland Tomography Scanners, X-Ray Computed Tomography, X-Ray Computed Bismuth HSJ IMA