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Proceedings Paper

Image-based dual energy CT improvements using Gram-Schmidt method
Author(s): Kyung-Kook Park; William Pavlicek; Thomas Boltz; Robert Paden; Amy Hara; Metin Akay
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Paper Abstract

Dual energy x-ray CT images are computed using either image or projection data. The latter is thought to be preferable for two-material decomposition. Nonetheless, using effective energies of polychromatic x-ray beams at separated kVp values, material decomposition and pseudo-monochromatic reconstruction can be performed from reconstructed images. This image-based approach generates added noise which should benefit from applying processing for noise reduction. A set of material attenuation information so produced defines a vector space, which represents the true material property but is predefined from mass attenuation coefficients of major body-composite materials. We assumed 53keV and 72keV x-ray effective energies for 80kVp and 140kVp dual energy CT. The Gram-Schmidt process was applied to remove noise orthogonal to the vector spaces of the body-composite materials. Two-material decomposition was performed, and monochromatic and density images were reconstructed. Evaluations of image noise, Hounsfield unit accuracy, and resolution with a phantom, as well as with abdominal images, demonstrates improved CNR and SNR without loss of detail. This method of noise suppression also produced high quality density maps of two basis materials. Since dual energy CT currently uses slightly above average radiation dose, this method has the potential for lowering dose in addition to improving image quality.

Paper Details

Date Published: 13 March 2009
PDF: 9 pages
Proc. SPIE 7258, Medical Imaging 2009: Physics of Medical Imaging, 72583S (13 March 2009); doi: 10.1117/12.811122
Show Author Affiliations
Kyung-Kook Park, Arizona State Univ. (United States)
William Pavlicek, Mayo Clinic (United States)
Thomas Boltz, Mayo Clinic (United States)
Robert Paden, Mayo Clinic (United States)
Amy Hara, Mayo Clinic (United States)
Metin Akay, Arizona State Univ. (United States)

Published in SPIE Proceedings Vol. 7258:
Medical Imaging 2009: Physics of Medical Imaging
Ehsan Samei; Jiang Hsieh, Editor(s)

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