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Proceedings Paper

A comparison of three CT voltage optimization strategies
Author(s): Kent M. Ogden; Walter Huda; Mohammad R. Khorasani; Ernest M. Scalzetti
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Paper Abstract

We evaluated three strategies for optimizing the x-ray tube voltage in chest CT examinations: (1) keeping patient dose constant and maximizing contrast to noise ratios (CNR); (2) keeping CNR constant and minimizing patient effective dose (E); (3) maximizing CNR2/E. Lung and soft tissue Hounsfield unit values, together with the corresponding image noise, were measured in a Rando phantom at x-ray tube voltages between 80 and 140 kV. A CT dosimetry software package (ImPACT) was used to compute effective doses as a function of CT x-ray tube voltage for adult patients undergoing chest CT examinations. CNR and patient dose in chest CT examinations both increase with increasing x-ray tube voltage at a fixed mAs. All optimization strategies provided similar qualitative results, which showed the best imaging performance was achieved at the lowest x-ray tube voltage (80 kV). Optimization using constant CNR or effective dose is preferred since these methods provide explicit choices of optimal kV/mAs combinations, as well as quantitative data on how changing kV would modify CNR and/or patient dose. The CNR2/Dose figure of merit does not offer explicit choices of kV/mAs for performing CT examinations, and changes in FOM value are more difficult to relate to changes in imaging performance or patient dose.

Paper Details

Date Published: 25 March 2008
PDF: 10 pages
Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 691351 (25 March 2008); doi: 10.1117/12.773305
Show Author Affiliations
Kent M. Ogden, SUNY Upstate Medical Univ. (United States)
Walter Huda, SUNY Upstate Medical Univ. (United States)
Mohammad R. Khorasani, SUNY Upstate Medical Univ. (United States)
Ernest M. Scalzetti, SUNY Upstate Medical Univ. (United States)

Published in SPIE Proceedings Vol. 6913:
Medical Imaging 2008: Physics of Medical Imaging
Jiang Hsieh; Ehsan Samei, Editor(s)

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