Repeatability and reproducibility of spectral results with clinical photon-counting CT: multi-center phantom study

Inter-institution repeatability of photon-counting CT spectral quantification improves with higher virtual monoenergetic image energy, with iodine 5 mg/mL RDC dropping from 20.6 to 4.1 HU from 50 to 150 keV across four institutions.

• Why it matters: Quantitative biomarkers need consistent spectral measurements across sites and time; inter-institution reproducibility for photon-counting CT remained unknown, limiting generalizability and clinical adoption.
• What they did: Four institutions scanned the same multi-energy phantom inserts on the same photon-counting CT model at 140 kV and CTDIvol 10 mGy, analyzing VMI (40–190 keV), iodine maps, and virtual non-contrast maps to compute mean error, sigma_ip, and repeatability/reproducibility coefficients.
• The result: Variation between institutions decreased and stabilized as VMI energy increased; at VMI 70 keV, sigma_ip was 1.3 HU (blood 70), 3.8 HU (adipose), and 2.7 HU (iodine 5 mg/mL), while iodine maps and VNC showed RDC ranges of 0.08–0.49 mg/mL and 3.5–10.9 HU, respectively.

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