Monochromatic CT image representation via fast switching dual kVp

Xiaoye Wu; David A. Langan; Dan Xu; Thomas M. Benson; Jed D. Pack; Andrea M. Schmitz; Eric J. Tkaczyk; Jaynne Leverentz; Paul Licato

doi:10.1117/12.811698

13 March 2009 Monochromatic CT image representation via fast switching dual kVp

Xiaoye Wu, David A. Langan, Dan Xu, Thomas M. Benson, Jed D. Pack, Andrea M. Schmitz, Eric J. Tkaczyk, Jaynne Leverentz, Paul Licato

Author Affiliations +

Proceedings Volume 7258, Medical Imaging 2009: Physics of Medical Imaging; 725845 (2009) https://doi.org/10.1117/12.811698
Event: SPIE Medical Imaging, 2009, Lake Buena Vista (Orlando Area), Florida, United States

Abstract

In a conventional X-ray CT system, where an object is scanned with a selected incident x-ray spectrum, or kVp, the reconstructed images only approximate the linear X-ray attenuation coefficients of the imaged object at an effective energy of the incident X-ray beam. The errors are primarily the result of beam hardening due to the polychromatic nature of the X-ray spectrum. Modem clinical CT scanners can reduce this error by a process commonly referred to as spectral calibration. Spectral calibration linearizes the measured projection value to the thickness of water. However, beam hardening from bone and contrast agents can still induce shading and streaking artifacts and cause CT number inaccuracies in the image. In this paper, we present a dual kVp scanning method, where during the scan, the kVp is alternately switching between target low and high preset values, typically 80kVp and 140 kVp, with a period less than 1ms. The measured projection pairs are decomposed into the density integrals of two basis materials in projection space. The reconstructed density images are further processed to obtain monochromatic attenuation coefficients of the object at any desired energy. Energy levels yielding optimized monochromatic images are explored, and their analytical representations are derived.

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Xiaoye Wu, David A. Langan, Dan Xu, Thomas M. Benson, Jed D. Pack, Andrea M. Schmitz, Eric J. Tkaczyk, Jaynne Leverentz, and Paul Licato "Monochromatic CT image representation via fast switching dual kVp", Proc. SPIE 7258, Medical Imaging 2009: Physics of Medical Imaging, 725845 (13 March 2009); https://doi.org/10.1117/12.811698

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