ABSTRACT
PURPOSE: To assess the overall imaging performance (radiation dose and image quality) of a photon-counting detector CT (PCD-CT) in comparison with a state-of-the-art energy-integrating detector CT (EID-CT) in run-off CTAs. METHODS: Consecutive patients who underwent run-off CTA on a PCD-CT were included (PCD-CT cohort). A retrospective cohort of patients who had undergone run-off CTA on an EID-CT was matched for gender, body mass index, height, and age (EID-CT cohort). Virtual monoenergetic imaging (VMI) reconstructions for various keV settings (40-120 keV) were generated. CT values and noise were semiautomatically measured for 13 vascular segments of the abdomen, pelvis, and lower extremities. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for each segment. Subjective image quality was evaluated by two radiologists along the dimensions 'vessel attenuation', 'vessel sharpness', and 'overall image quality' using 5-point Likert scales. RESULTS: Forty patients (age 70.9 ± 9.8 years; 14 women) were included in the PCD-CT cohort and matched with a corresponding number of EID-CT patients. Overall, there was an inverse correlation of signal and noise but also of SNR and CNR with keV levels used for VMI reconstructions. SNR and CNR in the 40 - 60 keV range exceeded EID-CT levels significantly. Subjective image quality was substantially higher at lower keV levels and showed no significant difference to EID-CT. CONCLUSION: Low keV VMI reconstructions of run-off CTA scans on a PCD-CT result in substantially higher SNR and CNR than 80 kVp and 100 kVp EID-CT acquisitions with equal subjective image quality.
