A spectral CT technique using balanced K-edge filter set

Yothin Rakvongthai; William Worstell; Georges El Fakhri; Jinsong Ouyang

doi:10.1117/12.2043747

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19 March 2014 A spectral CT technique using balanced K-edge filter set

Yothin Rakvongthai, William Worstell, Georges El Fakhri, Jinsong Ouyang

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Proceedings Volume 9033, Medical Imaging 2014: Physics of Medical Imaging; 90335M (2014) https://doi.org/10.1117/12.2043747
Event: SPIE Medical Imaging, 2014, San Diego, California, United States

Abstract

In this work, we propose a novel spectral computed tomography (CT) approach that combines a conventional CT scanner with a Ross spectrometer to obtain quasi-monoenergetic measurements. The Ross spectrometer, which is a generalization of a Ross filter pair, is a set of balanced K-edge filters whose thicknesses are such that the transmitted spectra through any two filters are nearly identical except in the energy band between their respective K-edges. The proposed approach is based on these specially designed filters, which are used to synthesize a set of quasi-monoenergetic sinograms whose reconstruction yields energy-dependent attenuation coefficient (μ_E) images. In this way, we are able to collect data using conventional CT data acquisition electronics, then to synthesize spectral CT datasets with highly stable, rate-independent energy bin boundaries. This approach avoids the chromatic distortion due to event pile-up which can cause difficulties with single photon spectrometry-based methods. To validate our Ross Spectrometer CT concept, we performed phantom studies and acquired data with a balanced filter set consisting of thin foils of silver, tin, cerium, dysprosium and tungsten. For each energy bin, a synthesized quasi-monoenergetic CT image was reconstructed using the filtered back projection (FBP) algorithm operating on the logarithmic ratio of corresponding energy-resolved intensity and blank sinogram pairs. The reconstructed attenuation coefficients showed satisfactorily good agreement with NIST reference values of μ_E for water. The proposed spectral CT technique is potentially feasible and holds promise to provide a more accurate and cost-effective alternative to single-photon counting spectral CT techniques.

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Yothin Rakvongthai, William Worstell, Georges El Fakhri, and Jinsong Ouyang "A spectral CT technique using balanced K-edge filter set", Proc. SPIE 9033, Medical Imaging 2014: Physics of Medical Imaging, 90335M (19 March 2014); https://doi.org/10.1117/12.2043747

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