Fast kV switching for improved material decomposition with photon counting x-ray detectors

Abstract

Photon counting x-ray detectors enable spectral imaging, which can be utilized for material decomposition and quantitative imaging tasks. This study investigates potential benefits of tube voltage optimization, including fast kV switching, on material decomposition noise. In simulation studies, single kV scans including 80/100/120/140 kV were tested as well as an 80/140 fast kV switching pair. Fluences of spectra were normalized with respect to CTDI to keep dose neutral. An open-source spectral response model of a realistic Si detector was used in the Cramér–Rao lower bound calculation, which estimates the lower bound of the noise in material decomposition. A simulated CT scan of an anthropomorphic head phantom was performed for noise analysis in the image domain. Simulation results showed that a single kV can be optimized for specific imaging tasks depending on the object size, while fast kV switching can substantially reduce the noise in material decomposition compared to single kV scan. Additionally, noise can be further reduced with a fixed Kedge (Gd) filter during fast kV switching acquisitions.