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Proceedings Paper

Monte Carlo investigation of backscatter factors for skin dose determination in interventional neuroradiology procedures
Author(s): Artur Omar; Hamza Benmakhlouf; Maria Marteinsdottir; Robert Bujila; Patrik Nowik; Pedro Andreo
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Paper Abstract

Complex interventional and diagnostic x-ray angiographic (XA) procedures may yield patient skin doses exceeding the threshold for radiation induced skin injuries. Skin dose is conventionally determined by converting the incident air kerma free-in-air into entrance surface air kerma, a process that requires the use of backscatter factors. Subsequently, the entrance surface air kerma is converted into skin kerma using mass energy-absorption coefficient ratios tissue-to-air, which for the photon energies used in XA is identical to the skin dose. The purpose of this work was to investigate how the cranial bone affects backscatter factors for the dosimetry of interventional neuroradiology procedures. The PENELOPE Monte Carlo system was used to calculate backscatter factors at the entrance surface of a spherical and a cubic water phantom that includes a cranial bone layer. The simulations were performed for different clinical x-ray spectra, field sizes, and thicknesses of the bone layer. The results show a reduction of up to 15% when a cranial bone layer is included in the simulations, compared with conventional backscatter factors calculated for a homogeneous water phantom. The reduction increases for thicker bone layers, softer incident beam qualities, and larger field sizes, indicating that, due to the increased photoelectric crosssection of cranial bone compared to water, the bone layer acts primarily as an absorber of low-energy photons. For neurointerventional radiology procedures, backscatter factors calculated at the entrance surface of a water phantom containing a cranial bone layer increase the accuracy of the skin dose determination.

Paper Details

Date Published: 19 March 2014
PDF: 8 pages
Proc. SPIE 9033, Medical Imaging 2014: Physics of Medical Imaging, 90331T (19 March 2014); doi: 10.1117/12.2042159
Show Author Affiliations
Artur Omar, Karolinska Univ. Hospital (Sweden)
Hamza Benmakhlouf, Karolinska Univ. Hospital (Sweden)
Univ. of Stockholm (Sweden)
Maria Marteinsdottir, Karolinska Univ. Hospital (Sweden)
Robert Bujila, Karolinska Univ. Hospital (Sweden)
Patrik Nowik, Karolinska Univ. Hospital (Sweden)
Pedro Andreo, Univ. of Stockholm (Sweden)

Published in SPIE Proceedings Vol. 9033:
Medical Imaging 2014: Physics of Medical Imaging
Bruce R. Whiting; Christoph Hoeschen, Editor(s)

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