Evaluating Spectral Performance for Quantitative Contrast-Enhanced Breast CT with a GaAs based Photon Counting Detector: A Simulation Approach.

Quantitative contrast-enhanced breastcomputed tomography (CT) has the potential to improve the diagnosis and management of breast cancer. Traditional methods using energy-integrated detectors and dual-exposure images with different incident spectra for material discrimination can increase patient radiation dose and be susceptible to motion artifacts and spectral resolution loss. Photon Counting Detectors (PCDs) offer a promising alternative approach, enabling acquisition of multiple energy levels in a single exposure and potentially better energy resolution. Gallium arsenide (GaAs) is particularly promisingfor breast PCD-CT due to its high quantum efficiency and reduction of fluorescence X-rays escaping the pixel within the breast imaging energy range. In this study, the spectral performance of a GaAs PCD for quantitative iodine contrast-enhanced breast CT was evaluated.

A GaAs detector with a pixel size of 100 μm, a thickness of 500 μm was simulated. Simulations were performed using cylindrical phantoms of varying diameters (10 cm, 12 cm, and 16 cm) with different concentrations and locations of iodine inserts, using incident spectra of 50, 55, and 60 kVp with 2 mm of added aluminum filtration and one exposure level corresponding to a Mean Glandular Doses (MGD) of approximately 10 mGy. We accounted for the effects of beam hardening and energy detector response using TIGRE CT open-source software and the publicly available Photon Counting Toolkit (PcTK). Material-specific images of the breast were produced using both projection and image-based material decomposition methods, and iodine component images were used to estimate iodine intake. Accuracy and precision of the proposed methods forestimating iodine concentration in breast CT images were assessed for different material decomposition methods, incident spectra, and breastphantom thicknesses.

The results showed that both the beam hardening effect and imperfection in the detector response had a significant impact on performance in terms of Root Mean Squared Error (RMSE), precision, and accuracy of estimati.