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 (μE) 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 μE 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.
