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

Objective 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. Materials and methods A spectral phantom was scanned using SPCCT and dual-energy CT (EID-DECT) at 8.5 mGy (CTDI vol ). 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 iDose 4 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. Results Noise magnitude (-22.4 ± 0.8%) and noise texture ( f av ) values were lower (-21.3 ± 4.4%), but spatial resolution ( f 50 ) was higher (5.8 ± 3.4%) with STD-B than with HRB at all iDose 4 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 iDose 4 levels and with both kernels, f av or f 50 values were higher with SPCCT, except for f 50 at i11 with HRB. Conclusion 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. Key Points 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.