A Tunable Energy Filter for Medical X-Ray Imaging

A multiprism lens (MPL) is a refractive X-ray lens, and its chromatic properties can be employed in an energy filtering setup to obtain a narrow tunable X-ray spectrum. We present the first evaluation of such a filter for medical X-ray imaging. The experimental setup yields a 6.6 gain of flux at 20 ￠ € ‰keV, and we demonstrate tunability by altering the energy spectrum to center also around 17 and 23 ￠ € ‰keV. All measurements are found to agree well with ray-tracing and a proposed geometrical model. Compared to a model mammography system with absorption filtering, the experimental MPL filter reduces dose 13 ￠ € “25% for 3 ￠ € “7 ￠ € ‰cm breasts if the spectrum is centered around the optimal energy. Additionally, the resolution is improved 2.5 times for a 5 ￠ € ‰cm breast. The scan time is increased 3 times but can be reduced with a slightly decreased energy filtering and resolution.