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Proceedings Paper

Monte Carlo modeling of the scatter radiation doses in IR
Author(s): Eugene Mah; Wenjun He; Walter Huda; Hai Yao; Bayne Selby
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Paper Abstract

Purpose: To use Monte Carlo techniques to compute the scatter radiation dose distribution patterns around patients undergoing Interventional Radiological (IR) examinations. Method: MCNP was used to model the scatter radiation air kerma (AK) per unit kerma area product (KAP) distribution around a 24 cm diameter water cylinder irradiated with monoenergetic x-rays. Normalized scatter fractions (SF) were generated defined as the air kerma at a point of interest that has been normalized by the Kerma Area Product incident on the phantom (i.e., AK/KAP). Three regions surrounding the water cylinder were investigated consisting of the area below the water cylinder (i.e., backscatter), above the water cylinder (i.e., forward scatter) and to the sides of the water cylinder (i.e., side scatter). Results: Immediately above and below the water cylinder and in the side scatter region, values of normalized SF decreased with the inverse square of the distance. For z-planes further away, the decrease was exponential. Values of normalized SF around the phantom were generally less than 10-4. Changes in normalized SF with x-ray energy were less than 20% and generally decreased with increasing x-ray energy. At a given distance from region where the x-ray beam enters the phantom, the normalized SF was higher in the backscatter regions, and smaller in the forward scatter regions. The ratio of forward to back scatter normalized SF was lowest at 60 keV and highest at 120 keV. Conclusion: Computed SF values quantify the normalized fractional radiation intensities at the operator location relative to the radiation intensities incident on the patient, where the normalization refers to the beam area that is incident on the patient. SF values can be used to estimate the radiation dose received by personnel within the procedure room, and which depend on the imaging geometry, patient size and location within the room. Monte Carlo techniques have the potential for simulating normalized SF values for any arrangement of imaging geometry, patient size and personnel location and are therefore an important tool for minimizing operator doses in IR.

Paper Details

Date Published: 16 March 2011
PDF: 11 pages
Proc. SPIE 7961, Medical Imaging 2011: Physics of Medical Imaging, 79613H (16 March 2011); doi: 10.1117/12.878303
Show Author Affiliations
Eugene Mah, Medical Univ. of South Carolina (United States)
Wenjun He, Clemson Univ. (United States)
Walter Huda, Medical Univ. of South Carolina (United States)
Hai Yao, Clemson Univ. (United States)
Bayne Selby, Medical Univ. of South Carolina (United States)

Published in SPIE Proceedings Vol. 7961:
Medical Imaging 2011: Physics of Medical Imaging
Norbert J. Pelc; Ehsan Samei; Robert M. Nishikawa, Editor(s)

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