In this study, we propose a novel approach to dual-energy contrast-enhanced digital mammography, with the development of a dual-energy recombination algorithm based on an image chain model and the determination of the associated optimal low and high-energy techniques. Our method produces clutter-free iodine-equivalent images and includes thickness correction near the breast border. After the algorithm description, the optimal low and high-energy acquisition techniques are determined to obtain a compromise between image quality and glandular dose. The low and high-energy techniques were chosen to minimize the glandular dose for a target Signal Difference to Noise Ratio (SDNR) in the dual-energy recombined image. The theoretical derivation of the iodine SDNR in the recombined image allowed the prediction of the optimal low and high-energy techniques. Depending on the breast thickness and glandular percentage, the optimal low-energy kVp and mAs ranged from 24kVp (Mo/Mo or Mo/Rh) to 35kVp (Rh/Rh), and from 60 to 90mAs respectively, and the high-energy kVp and mAs ranged from 40kVp to 47kVp (Mo/Cu), and from 80mAs to 290mAs. We proved the better performance of our algorithm compared to the classic weighted logarithmic subtraction method in terms of patient dose and also in terms of texture cancelation, through the use of artificial textured images. Values of iodine contrast measured on phantom were close to the expected iodine thickness. Good correlation was found between the measured and theoretical iodine SDNR in the dual-energy images, which validates our theoretical optimization of the acquisition techniques.

Tomosynthesis is a 3-dimensional mammography technique that generates thin slices separated one to the other by typically 1 mm from source data sets. The relatively high image noise in these thin slices raises the value of 1-cm thick slices computed from the set of reconstructed slices for image interpretation. In an initial evaluation, we investigated the potential of different algorithms for generating thick slices from tomosynthesis source data (maximum intensity projection-MIP; average algorithm-AV, and image generation by means of a new algorithm, so-called softMip). The three postprocessing techniques were evaluated using a homogeneous phantom with one textured slab with a total thickness of about 5 cm in which two 0.5-cm-thick slabs contained objects to simulate microcalcifications, spiculated masses, and round masses. The phantom was examined by tomosynthesis (GE Healthcare). Microcalcifications were simulated by inclusion of calcium particles of four different sizes. The slabs containing the inclusions were examined in two different configurations: adjacent to each other and close to the detector and with the two slabs separated by two 1-cm thick breast equivalent material slabs. The reconstructed tomosynthesis slices were postprocessed using MIP, AV, and softMip to generate 1-cm thick slices with a lower noise level. The three postprocessing algorithms were assessed by calculating the resulting contrast versus background for the simulated microcalcifications and contrast-to-noise ratios (CNR) for the other objects. The CNRs of the simulated round and spiculated masses were most favorable for the thick slices generated with the average algorithm, followed by softMip and MIP. Contrast of the simulated microcalcifications was best for MIP, followed by softMip and average projections. Our results suggest that the additional generation of thick slices may improve the visualization of objects in tomosynthesis. This improvement differs from the different algorithms for microcalcifications, speculated objects, and round masses. SoftMip is a new approach combining features of MIP and average showing image properties in between MIP and AV.

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Dual-energy imaging with the injection of an iodinated contrast medium has the potential to depict cancers in the breast, by the demonstration of tumour angiogenesis and the suppression of the breast structure noise. The present study investigates the optimum monoenergetic beam parameters for this application. First, a theoretical study of the beam parameters was performed to find the best compromise between the quality of the dualenergy recombined image and the patient dose. The result of this analysis was then validated by phantom experiments using synchrotron monoenergetic radiation at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). For an average breast of 5cm thickness and 50% glandularity, the theoretical simulations show an optimum at 20 keV for the low energy and 34 keV for the high energy, for a CsI detector of a standard mammography system. The SDNR variations with the low energy, the high energy or the dose repartition are very similar between the measurements on images acquired with synchrotron radiation and the simulated values. This ensures the accuracy of our theoretical optimization and the validity of the optimal beam parameters found in this study. The aim of this work is to demonstrate the potential of Dual-Energy CEDM (Contrast Enhanced Digital Mammography) with ideal monoenergetic sources, in order to provide an indicator of how to shape the polyenergetic spectra produced with classical X-ray sources for this application.

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