Optimization of spectral photon-counting CT reconstruction parameters for improved detection of peritoneal metastases compared with energy-integrating detector dual-energy CT: a phantom study

Abstract

To determine the best combination of reconstruction parameters on a spectral photon-counting CT (SPCCT) system to improve detection of peritoneal metastases (PMs) on virtual monoenergetic images (VMIs) at 40 keV. A spectral phantom was scanned using SPCCT and dual-energy CT (EID-DECT) at 8.5 mGy (CTDIvol). 40 keV VMIs were reconstructed on EID-DECT using a level 4 Spectral algorithm and kernel B. For SPCCT, two reconstruction kernels (STD-B and HRB) and four iDose4 levels (i5/i7/i9/i11) were used. Noise power spectrum (NPS) and task-based transfer function (TTF) were analyzed. Detectability indices (d’) for non-mucinous and mucinous peritoneal metastases (nmPMs and mPMs) were calculated. Noise magnitude (-22.4 ± 0.8%) and noise texture (fav) values were lower (-21.3 ± 4.4%), but spatial resolution (f50) was higher (5.8 ± 3.4%) with STD-B than with HRB at all iDose4 levels. For both simulated PMs, d’ values were higher with STD-B than with HRB (22.3 ± 0.3%). Compared to EID-DECT, noise magnitude and d’ values were similar or better with STD-B at i7/i9/i11 and i9/i11 for HRB. At all iDose4 levels and with both kernels, fav or f50 values were higher with SPCCT, except for f50 at i11 with HRB. Optimized reconstruction settings on SPCCT offer better image quality and lesion detectability on 40 keV VMIs than EID-DECT. Combining the STD-B kernel with level i9 achieved the best compromise between noise texture, spatial resolution, and detectability for simulated PMs. Question Can the performance of a spectral photon-counting CT (SPCCT) improve detection of peritoneal metastases (PM on 40 keV images compared with a conventional dual-energy CT (EID-DECT) system? Findings SPCCT with optimized reconstruction settings improved image noise, spatial resolution, and lesion detectability compared with EID-DECT at 40 keV. Relevance Statement SPCCT may enhance the preoperative assessment of colorectal cancer patients by better visualizing small or low-contrast peritoneal lesions. Validation in larger clinical cohorts is required to confirm these findings and define standardized reconstruction protocols.