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There has recently been renewed interest in quantitative iodinated contrast-enhanced breast imaging, sometimes referred to as contrast-enhanced spectral mammography (CESM). Photon-counting detectors (PCDs) have a number of benefits for iodinated contrast-enhanced imaging over dual-energy systems (using energy integrating detectors), one of which is the capability of acquiring multi-bin data with one exposure. Most PCDs and prototype systems being developed are using CdTe or CZT sensor material which have non-optimal characteristic X-ray emission with energies in the range used for breast imaging. This increases charge sharing and, hence, spectral degradation. Recently, a new PCD has been developed using a GaAs sensor. Since GaAs has lower energy characteristic x-rays (lower than CdTe), it is expected that this new PCD detector might be beneficial for spectral x-ray breast imaging. In this work, we have theoretically compared the two detector materials in terms of iodine quantification using the Cramer-Rao lower bound (CRLB) as a figure of merit. Four different experiments were performed, each comparing the performance of CdTe and GaAs: 1) sensitivity of iodine quantification to charge cloud size and electronic noise, 2) effect of dose and photon spectrum on iodine quantification, 3) how the CRLB changes with the number of energy bins, and 4) a dose analysis study to assess any possible dose reduction offered by either detector. Simulations of both the CdTe and GaAs PCDs were performed using the Photon Counting Toolkit (PcTK) software. Three sets of 5000 noise realizations were used to calculate the CRLB of iodine quantification in each study. Results of these studies suggest that GaAs is a promising detector material for contrast-enhanced spectral mammography
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