Image subtraction in both SE and DE CEDM reduces β by over a factor of 2, while maintaining α below that in DM. Given the equivalent α between SE and DE unprocessed CEDM images, and the smaller anatomical noise in the DE subtracted images, the DE approach may have an advantage over SE CEDM. It will be necessary to test this potential advantage in future lesion detectability experiments, which account for realistic lesion signals. The authors' results suggest that LE images could be used in place of DM images in CEDM exam interpretation.

Abstract. The objective is to optimize low-energy (LE) and high-energy (HE) exposure parameters of contrastenhanced spectral mammography (CESM) examinations in four different clinical applications for which different levels of average glandular dose (AGD) and ratios between LE and total doses are required. The optimization was performed on a Senographe DS with a SenoBright® upgrade. Simulations were performed to find the optima by maximizing the contrast-to-noise ratio (CNR) on the recombined CESM image using different targeted doses and LE image quality. The linearity between iodine concentration and CNR as well as the minimal detectable iodine concentration was assessed. The image quality of the LE image was assessed on the CDMAM contrastdetail phantom. Experiments confirmed the optima found on simulation. The CNR was higher for each clinical indication than for SenoBright®, including the screening indication for which the total AGD was 22% lower. Minimal iodine concentrations detectable in the case of a 3-mm-diameter round tumor were 12.5% lower than those obtained for the same dose in the clinical routine. LE image quality satisfied EUREF acceptable limits for threshold contrast. This newly optimized set of acquisition parameters allows increased contrast detectability compared to parameters currently used without a significant loss in LE image quality.

Abstract. Contrast-enhanced digital mammography (CEDM), promises to improve diagnostic accuracy as an adjunct to mammography, especially for women with dense breasts. Here we review 98 enhancing lesions from a previously published dual-energy CEDM study of 120 women to identify enhancing lesion morphologies and to characterize their sizes and margins as detected in CEDM. We have designed a phantom based on these clinical data that incorporates realistic enhancing lesion morphologies for CEDM evaluation. The phantom includes elements of four lesion types observed in CEDM, which broadly follow analogous categories developed from the MRI Breast Imaging, Reporting and Data System (BI-RADS) lexicon. This phantom uses solid iodinated plastic features with accurate iodine concentrations for detection sensitivity experiments. We believe that comparisons of the lesion morphologies through quantitative metrics and reader studies will be useful to test lesion classification and discrimination tasks that can contribute to CEDM performance evaluation.Keywords: CEDM dual-energy mammography iodine morphology phantom. IntroductionContrast-enhanced digital mammography promises to be a cost-effective and accurate alternative to breast MRI to assess hypervascularized tissues that may be related to tumour angiogenesis [1,2]. One approach to CEDM is a dual-energy (DE) technique, where an iodinated contrast agent is administered intravenously and then a pair of low-energy (LE) and high-energy (HE) mammograms are acquired with mean x-ray beam energies below and above the iodine K-edge [3]. The LE and HE images are combined in a manner to cancel the appearance of normal breast tissue and to reveal regions of increased iodine uptake. Currently, there are no standardized classifications for radiologists reporting on CEDM tumour morphology, and relatively few published * Corresponding author.

Abstract. Some limitations of mammography that particularly affect diagnosis of women with dense breasts, such as tissue superposition and marginal cancer image contrast, can be overcome with the use of contrast-enhanced digital mammography (CEDM). CEDM uses iodinated contrast agents to increase attenuation in areas exhibiting hyper-vascularization, potentially due to tumour angiogenesis, and image subtraction to cancel normal tissue signal. Here, we propose a method for objective task-based image quality evaluation of CEDM that can be routinely carried out in the clinic. A phantom was designed with features that allow for practical measurements of MTF, NPS, and iodine contrast that were used to estimate a CEDM detectability index for a given imaging task. We present results from several months of weekly testing of a commercial dualenergy CEDM system. From these data, we demonstrate measurement sensitivity to variations from standard acquisition conditions, suggesting the potential to identify system failure modes using this approach.

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