Evaluation of a personalized total iodine dose (TID) combined with fixed injection duration (FID) protocol using high-concentration (400 mgI/mL) iodinated contrast medium in CT portal venography: a randomized trial

Abstract

Background The portal vasculature is closely associated with clinical outcomes in liver disease. Contrast-enhanced computed tomography (CT) serves as the first-line noninvasive tool for its evaluation. The contrast administration strategy critically influences CT image quality and diagnostic performance. This study aimed to investigate the effect of a personalized total iodine dose (TID) combined with a fixed injection duration (FID) protocol on CT imaging of the portal vein using a high-concentration iodine contrast medium (CM). Methods A GE 64-slice spiral CT scanner and a 400 mgI/mL iodine CM were used. The total CM dose was calculated based on the patient’s total body weight (TBW) at doses of either 400 or 450 mgI/kg. The FID was set at 18 or 20 s, and the tube voltage was set at 100 or 120 kVp. These three parameters were varied to generate eight distinct injection and scanning protocols. Eligible patients were randomized into eight groups. The CT values of the main portal vein (CTmpv), left superior branch of the portal vein (CTlspv), and liver parenchyma (CTliver), image noise, contrast-to-noise ratio (CNR), volume CT dose index (CTDIvol), and dose-length product (DLP) were measured. Additionally, overall image quality, portal vein lesion detection, liver lesion detectability, maximum intensity projection (MIP), and volume rendering (VR) reconstructions of the portal vein were evaluated. Results Lower tube voltage significantly increased CTmpv (P<0.001, partial η2=0.229), CTlspv (P<0.001, partial η2=0.127), CTliver (P<0.001, partial η2=0.089), and image noise (P<0.001, partial η2=0.118), while significantly reducing CTDIvol (P<0.001, partial η2=0.152) and DLP (P<0.001, partial η2=0.209). FID significantly affected CTmpv (P=0.039, partial η2=0.025) and CNR (P=0.009, partial η2=0.04) (both CTmpv and CNR were higher in the 20 s FID group than in the 18 s group). In the subjective evaluation, tube voltage significantly influenced portal vein lesion detection (P=0.004, partial η2=0.048); other scores (overall image quality, liver lesion detectability, VR, and MIP) showed no significant differences among the three factors, with no interactions. Meanwhile, the main effect of TID and FID, as well as all interaction effects, was non-significant (P>0.05). Conclusions When using high-concentration iodine CM, all imaging protocols achieved satisfactory portal vein enhancement. The protocol combining a lower flow rate (20-s FID), a lower TID (400 mgI/kg), and a tube voltage of 100 kVp improved portal vein CT values and reduced radiation dose without compromising image quality, and thus represents a promising protocol for clinical CT portal venography.