Spectral X-Ray Scatter Characterization with an Energy Resolved Photon Counting Detector*

Photon counting detectors with energy-resolving capabilities are being investigated for x-ray imaging in medical applications. Biological materials have only minor differences in their spectral attenuation properties, and therefore accurate estimations rely on the precise measurement of the transmitted x-ray beam. Scattered x-rays reaching the detector reduce image quality and distort the measured energy spectrum, contributing additional photon counts to lower energies. Previous work characterizing x-ray scatter has been limited to conventional energy-integrating detectors, which do not provide spectral information. Our work provides a detailed investigation of the spectral contributions of x-ray scattering from biological-equivalent material using energy-resolving photon counting detectors. We show that spectral distortions due to the object scatter produce large quantitative inaccuracies, particularly at low energies where image contrast is optimal. These spectral distortions are reduced by increasing the distance between the scattering sample, though remain unsatisfactory for sample thicknesses relevant to mammography.