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Proceedings Paper

Anatomy-based transmission factors for technique optimization in portable chest x-ray
Author(s): Christopher L. Liptak; Deborah Tovey; William P. Segars; Frank D. Dong; Xiang Li
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Paper Abstract

Portable x-ray examinations often account for a large percentage of all radiographic examinations. Currently, portable examinations do not employ automatic exposure control (AEC). To aid in the design of a size-specific technique chart, acrylic slabs of various thicknesses are often used to estimate x-ray transmission for patients of various body thicknesses. This approach, while simple, does not account for patient anatomy, tissue heterogeneity, and the attenuation properties of the human body. To better account for these factors, in this work, we determined x-ray transmission factors using computational patient models that are anatomically realistic. A Monte Carlo program was developed to model a portable x-ray system. Detailed modeling was done of the x-ray spectrum, detector positioning, collimation, and source-to-detector distance. Simulations were performed using 18 computational patient models from the extended cardiac-torso (XCAT) family (9 males, 9 females; age range: 2-58 years; weight range: 12-117 kg). The ratio of air kerma at the detector with and without a patient model was calculated as the transmission factor. Our study showed that the transmission factor decreased exponentially with increasing patient thickness. For the range of patient thicknesses examined (12-28 cm), the transmission factor ranged from approximately 21% to 1.9% when the air kerma used in the calculation represented an average over the entire imaging field of view. The transmission factor ranged from approximately 21% to 3.6% when the air kerma used in the calculation represented the average signals from two discrete AEC cells behind the lung fields. These exponential relationships may be used to optimize imaging techniques for patients of various body thicknesses to aid in the design of clinical technique charts.

Paper Details

Date Published: 18 March 2015
PDF: 9 pages
Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 941247 (18 March 2015); doi: 10.1117/12.2082056
Show Author Affiliations
Christopher L. Liptak, Cleveland State Univ. (United States)
Deborah Tovey, The Cleveland Clinic (United States)
William P. Segars, Duke Univ. Medical Ctr. (United States)
Frank D. Dong, The Cleveland Clinic (United States)
Xiang Li, Cleveland State Univ. (United States)

Published in SPIE Proceedings Vol. 9412:
Medical Imaging 2015: Physics of Medical Imaging
Christoph Hoeschen; Despina Kontos, Editor(s)

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