Quantitative analysis of the effect of energy separation in k-edge digital subtraction imaging

The aim of the work is to quantitatively compare the effect of the energy separation in the k-edge digital subtraction imaging technique. Images of a custom-made, iodine filled (k-edge = 33.17 keV) test object have been acquired with monochromatic x-ray beams (energy spread <0.1 keV) at the ID17 biomedical beamline of the ESRF. Image acquisition has been performed using two energy separations, namely 0.65 keV (32.85 keV and 33.5 keV, respectively) and 4.4 keV (31.2 keV and 35.6 keV, respectively), using beams of energies on either side of the iodine k-edge. Signal and signal-to-noise ratio (SNR) analysis has been performed as a function of ΔE and the contrast medium concentrations. The results show that the SNR values measured for ΔE < 1 keV are only slightly higher than those measured for ΔE = 4.4 keV. This preliminary study shows that monochromaticity and the energy separation obtained with quasi monochromatic beams from conventional x-ray sources might be suitable for this imaging technique.