Evaluation of multi-keV PureCalcium images from photon-counting CT for abdominal imaging: A comparison with true and conventional virtual non-contrast images.

PURPOSE: To determine which keV PureCa images can effectively substitute TNC images for abdominal imaging.

METHODS

A total of 50 consecutive patients who underwent thoracoabdominal scans on Photon-Counting CT from January to April 2025 were included. A true non-contrast (TNC), arterial (CTA) and venous (CTV) phase images were analyzed. Conventional virtual non-contrast (VNC) and 5 PureCa images were reconstructed from each contrast phase. Attenuation values and noise on 12 regions of interest were measured. Overall image quality, contrast removal and calcium preservation were analyzed using a 5-point scale. The paired t-tests and Friedman tests were applied to compare objective and subjective results.

RESULTS

70 keV yielded the smallest HUerror in the majority of abdominal tissues during the arterial and venous phase. The overall trend demonstrated a plateau in noise reduction beyond 65 keV. Compared with VNC images, PureCa demonstrated significantly lower HUerror in key soft tissues: Liver: 2 (1-6) HU vs 5 (3-8) HU (P = 0.001), Muscle: 2 (1-4) HU vs 10 (7-14) HU (P < 0.001), subcutaneous adipose tissue: 2.5 (1-4) HU vs 39 (33-42) HU (P < 0.001). All patients had a subjective score of 3 or above. 65-70 keV PureCa images were rated significantly higher than 50-60 keV images, and comparable to VNC, but still inferior to TNC (P < 0.05).

CONCLUSIONS

PureCa images reconstructed at 70 keV on photon-counting CT systems provide accurate attenuation values and satisfactory image quality for abdominal tissues.