Towards quantitative spectral mammography using triple-energy K-edge imaging and a two-pass reconstruction approach

This paper introduces a novel approach to quantitative contrast-enhanced spectral mammography (CESM) using triple energy K-edge imaging and a two-pass material decomposition method. The primary objective is to accurately determine local projected iodine concentration by leveraging the iodine K-edge in presence of glandular and adipose breast tissue. Addressing the ill-posed problem of established dual-energy methods, our approach accounts for three base materials with three non-redundant measurements. The proposed method involves two key steps. First, we estimate the local total thickness D via three material decomposition with the use of an iterative beam hardening correction, followed by strong denoising. Second, we use D as a constraint computing the recombined iodine image in classical dual-energy technique. In addition based on noise propagation the dose distribution and tube voltage for each image was optimized with respect to minimize standard deviation. Simulation studies using a numerical CIRS dual-energy phantom demonstrate thickness independent effective background cancellation, accurate reconstruction of relative projected iodine concentrations at moderate image noise levels. Sensitivity to remaining inaccuracies was simulated by adding scatter and deviation of used spectra for reconstruction and beam hardening correction. Furthermore, measurements were performed in laboratory system to test the feasibility. In conclusion, the proposed method provides a robust theoretical framework for accurately reconstructing projected iodine concentration images in CESM. For real measurements the method requires a highly accurate estimation of x-ray spectrum and knowledge of attenuation values.