Performance evaluation of a sub-millimeter spectrallyresolved CT system on pediatric imaging tasks: a simulation

摘要

We are developing a photon counting silicon strip detector with 0.4 x 0.5 mm2 square detector elements for clinical CT applications. Except the somewhat limited detection efficiency at higher kVp's the largest discrepancies from ideal spectral behavior have been shown to be Compton interactions in the detector combined with electronic noise. Using the framework of cascaded systems analysis, we reconstruct the 3D MTF and NPS of a silicon strip detector using "optimal" projection based weighting, including the influence of scatter and charge sharing inside the detector. We compare the reconstructed noise and signal characteristics with a reconstructed 3D MTF and NPS of an ideal energy integrating detector by calculating the detectability index for several clinically relevant imaging task. This work demonstrates that although the detection efficiency of the silicon detector rapidly drops for the acceleration voltages encountered in clinical computed tomography practice and the high fraction of Compton interactions due to the low atomic number, silicon detectors can perform on par with ideal energy integrating detectors for routine imaging tasks contaning low frequency components. For imaging task containing high frequency components, silicon detectors can perform approximately 1.4 — 1.8 times better than a fully ideal energy integrating system with unity detection, no scatter or charge sharing inside the detector and 1 x 1 mm2 square detector elements.