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Proceedings Paper

Skin dose mapping for non-uniform x-ray fields using a backscatter point spread function
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Paper Abstract

Beam shaping devices like ROI attenuators and compensation filters modulate the intensity distribution of the xray beam incident on the patient. This results in a spatial variation of skin dose due to the variation of primary radiation and also a variation in backscattered radiation from the patient. To determine the backscatter component, backscatter point spread functions (PSF) are generated using EGS Monte-Carlo software. For this study, PSF’s were determined by simulating a 1 mm beam incident on the lateral surface of an anthropomorphic head phantom and a 20 cm thick PMMA block phantom. The backscatter PSF’s for the head phantom and PMMA phantom are curve fit with a Lorentzian function after being normalized to the primary dose intensity (PSFn). PSFn is convolved with the primary dose distribution to generate the scatter dose distribution, which is added to the primary to obtain the total dose distribution. The backscatter convolution technique is incorporated in the dose tracking system (DTS), which tracks skin dose during fluoroscopic procedures and provides a color map of the dose distribution on a 3D patient graphic model. A convolution technique is developed for the backscatter dose determination for the nonuniformly spaced graphic-model surface vertices. A Gafchromic film validation was performed for shaped x-ray beams generated with an ROI attenuator and with two compensation filters inserted into the field. The total dose distribution calculated by the backscatter convolution technique closely agreed with that measured with the film.

Paper Details

Date Published: 9 March 2017
PDF: 8 pages
Proc. SPIE 10132, Medical Imaging 2017: Physics of Medical Imaging, 101320U (9 March 2017); doi: 10.1117/12.2254257
Show Author Affiliations
Sarath Vijayan, Toshiba Stroke and Vascular Research Ctr., Univ. at Buffalo (United States)
Univ. at Buffalo (United States)
Zhenyu Xiong, Toshiba Stroke and Vascular Research Ctr., Univ. at Buffalo (United States)
Univ. at Buffalo (United States)
Alok Shankar, Toshiba Stroke and Vascular Research Ctr., Univ. at Buffalo (United States)
Univ. at Buffalo (United States)
Stephen Rudin, Toshiba Stroke and Vascular Research Ctr., Univ. at Buffalo (United States)
Univ. at Buffalo (United States)
Daniel R. Bednarek, Toshiba Stroke and Vascular Research Ctr., Univ. at Buffalo (United States)
Univ. at Buffalo (United States)


Published in SPIE Proceedings Vol. 10132:
Medical Imaging 2017: Physics of Medical Imaging
Thomas G. Flohr; Joseph Y. Lo; Taly Gilat Schmidt, Editor(s)

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