Evaluation of run-off computed tomography angiography on a first-generation photon-counting detector CT scanner – Comparison with low-kVp energy-integrating CT

Abstract

PurposeTo 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. MethodsConsecutive 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. ResultsForty 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. ConclusionLow 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.