Contrast-Enhanced Abdominal CT with Clinical Photon-Counting Detector CT: Assessment of Image Quality and Comparison with Energy-Integrating Detector CT

Abstract

To determine quantitative and qualitative image quality of contrast-enhanced abdominal photon-counting detector CT (PCD-CT) compared to energy-integrating detector CT (EID-CT) in the same patients. Thirty-nine patients (mean age 63 ± 10 years, 10 females, mean BMI 26.0 ± 5.7 kg/m2) were retrospectively included who underwent clinically indicated, contrast-enhanced abdominal CT in portal-venous phase with first-generation dual-source PCD-CT and who underwent previous abdominal CT with EID-CT. For both scan, same contrast media protocol was used. PCD-CT was performed in QuantumPlus mode (obtaining full spectral information) at 120kVp. EID-CT was performed using automated tube voltage selection (reference tube voltage 100kVp). In PCD-CT, virtual monoenergetic images (VMI) were reconstructed in 10keV intervals (40-90 keV). Tube current-time product in PCD-CT was modified in each patient to obtain same volume CT-dose-index (CTDIvol) as with EID-CT. Attenuation of organs and vascular structures were measured, noise quantified, and contrast-to-noise ratio (CNR) calculated. Two independent, blinded radiologists assessed subjective image quality using a 5-point Likert scale (overall image quality, image noise, contrast, and liver lesion conspicuity). Median time interval between the scan was 12 months. BMI (p=0.905) and CTDIvol (p=0.984) were similar between scans. CNRparenchymal and CNRvascular of VMI from PCD-CT at 40 and 50keV were significantly higher than EID-CT (all, p < 0.05). Overall, inter-reader agreement for all subjective image quality readings was substantial (Krippendorff's alpha=0.773). Overall image quality of VMI was rated similar at 50 and 60 keV compared to EID-CT (all, p > 0.05). Subjective image noise was significantly higher at 40-50 keV, contrast significantly higher at 40-60 keV (all, p < 0.05). Lesion conspicuity was rated similar on all images. Our intra-individual analysis of abdominal PCD-CT indicates that VMI at 50 keV shows significantly higher CNR at similar subjective image quality as compared to EID-CT at identical radiation dose.