Tailored versus fixed scan delay in contrast-enhanced abdominal multi-detector CT: An intra-patient comparison of image quality

Purpose: To perform an intra-patient comparison between a single-pass protocol (SP) and a portal venous phase (PVP) by means of both quantitative and qualitative analysis of image quality. Methods: Forty patients (31 M; 9F; aged 20–77 years; BMI 23 ± 4 Kg/m2) underwent both a SP and a PVP using a 64-rows multi-detector CT with a median interval time of 56 days (range 5–903). All patients underwent i.v. bolus injection (2.0 cc/sec) of 1.7 cc/Kg of a non ionic iodinated contrast-media (370 mgI/ml) with scan delays of 67 ± 8 and 90 s for the SP and the PVP, respectively. Signal- (SNR) and contrast-to-noise ratios (CNR) were calculated for most visceral organs and for both abdominal aorta (AA) and main portal vein (MPV). For qualitative analysis, reproduction of abdominal viscera and vascular structures was blindly evaluated and inter-observer agreement calculated by the weighted Cohen k-analysis. Results: Attenuation values (H.U.) of AA (232 ± 53 vs 180 ± 36) and MPV (215 ± 39 vs 187 ± 42) were significantly (p < 0.001) higher in the SP than in PVP, respectively. At qualitative analysis, reproduction of most abdominal viscera was also significantly sharper (p < 0.001) with the SP than the PVP with inter-observer agreement scores (k) ranging from 0.60 to 0.88 for all but one imaging criteria. Conclusions: As the SP resulted in a significantly higher vascular enhancement and in a sharper reproduction of most abdominal viscera, it may be better suited than a PVP for the CT evaluation of non traumatic acute abdomen.