Effects of energy-bin acquisition methods on noise properties in photon-counting spectral CT

Spectral CT with photon-counting detectors has the potential to improve material decomposition and contrastto- noise ratio (CNR) compared to conventional CT. This work compared the noise properties of two general energy-bin acquisition methods: (1) energy bins acquired from the same spectrum noise realization, and (2) energy bins acquired from different spectrum noise realizations. For both types of acquisitions, the detected number of counts per bin was simulated and measured on a bench-top system. The energy-bin noise standard deviation was compared for both acquisition methods. Simulations were performed to compare both methods with respect to noise in material decomposition estimates and the CNR in image-based weighted images. Both the experimental and simulation results indicated increased energy-bin noise when energy measurements were acquired from different spectrum realizations. The noise increased by a factor of 2 for the lowest energy bin, with the noise penalty decreasing with increasing bin energy. The simulation results demonstrated a factor of 1.2 to 2 increase in noise in material decomposition estimates when acquiring from different spectrum realizations. Despite the increased energy-bin noise, energy measurements from different spectrum realizations increased the CNR in image-based-weighted images by 10%, potentially due to noise correlations across bins. Overall, the investigated acquisition methods demonstrated differences in noise standard deviation, affecting material decomposition estimates and CNR.