Phits Simulation of a Stacked Silicon–Scintillator Detector for Next-Generation Spectral Ct
Abstract
Purpose
CT X-ray spectra were generated in PHITS by simulating bremsstrahlung at the tube anode. Using the resulting continuous CT spectrum as the incident beam, silicon response was evaluated for silicon thicknesses of 1, 5, and 10 mm to characterize energy deposition and spectral signatures relevant to prototype design. Under polyenergetic conditions, a simplified CT geometry will be modeled, and spectra in the silicon and downstream scintillator layers will be analyzed to evaluate energy separation and the feasibility of material decomposition. Simulated trends will further be compared with preliminary measurements acquired on a clinical CT system under comparable tube-voltage and geometric conditions.
Methods
CT X-ray spectra were generated in PHITS by simulating bremsstrahlung at the tube anode. Using the resulting continuous CT spectrum as the incident beam, silicon response was evaluated while varying silicon thickness (1, 5, and 10 mm) to characterize energy deposition and spectral signatures relevant to prototype design. Under polyenergetic conditions, a simplified CT geometry is modeled, and spectra in the silicon and downstream scintillator layers are analyzed to evaluate energy separation and the feasibility of material decomposition. Simulation trends are further compared with preliminary measurements acquired on a clinical CT system under comparable tube-voltage and geometric conditions.
Results
With the continuous-spectrum input, the silicon layer provided spectral discrimination at clinically relevant photon flux. Silicon absorption increased with thickness to ~5% (1 mm), ~25% (5 mm), and ~45% (10 mm). Tube-voltage changes shifted the incident spectrum and produced corresponding changes in the silicon response. Attenuation to the downstream scintillator was limited, suggesting minimal degradation of scintillator signal-to-noise.
Conclusion
PHITS results support the feasibility of a stacked silicon–scintillator detector for extracting spectral information while mitigating key limitations of conventional PCDs. Future work will extend simulations and experiments to image reconstruction and quantitative material identification.