  Dual-energy subtraction imaging (DES) is a method to improve the
detectability of contrast agents over a lumpy background. Two images, acquired
at x-ray energies above and below an absorption edge of the agent material, are
logarithmically subtracted, resulting in suppression of the signal from the
tissue background and a relative enhancement of the signal from the agent.
Although promising, DES is still not widely used in clinical practice. One
reason may be the need for two distinctly separated x-ray spectra that are
still close to the absorption edge, realized through dual exposures which may
introduce motion unsharpness. In this study, electronic spectrum-splitting with
a silicon-strip detector is theoretically and experimentally investigated for a
mammography model with iodinated contrast agent. Comparisons are made to
absorption imaging and a near-ideal detector using a signal-to-noise ratio that
includes both statistical and structural noise. Similar to previous studies,
heavy absorption filtration was needed to narrow the spectra at the expense of
a large reduction in x-ray flux. Therefore, potential improvements using a
chromatic multi-prism x-ray lens (MPL) for filtering were evaluated
theoretically. The MPL offers a narrow tunable spectrum, and we show that the
image quality can be improved compared to conventional filtering methods.
