Feasibility of half the recommended dose of IV contrast in DECT: image quality evaluation and diagnostic acceptability in cancer patients

Purpose: To assess the quality of dual-energy computed tomography (DECT) images in patients receiving 50% of the recommended weight-based volume of iodinated intravenous contrast medium.

Methods: The study included cancer patients who previously underwent abdominal CT on a DECT scanner using a single source with the full recommended weight-based dose of Iohexol 350. Using the same scanner, the patients underwent a portovenous phase DECT scan following intravenous injection of half of the recommended weight-based dose. Monochromatic energy images were processed at 60 and 70kEv and compared to polychromatic 140kVp images. Three radiologists independently scored the images for overall diagnostic acceptability and image quality of solid organs and vasculature. Regions of interest were drawn on the portal vein, aorta, liver, and fat to calculate contrast to noise ratio (CNR) and signal to noise ratio (SNR). A multivariate ordinal generalized estimating equations model was used to assess image quality score. Pairwise comparisons were performed of the readers' scores, CNR, and SNR. Agreement with respect to quality score was calculated by using Fleiss's kappa value.

Results: Diagnostic acceptability was better for the SECT (120kVp) scans than for the 70 and 60kEv scans, and better for the 70 and 60kEv scans than for the 140kVp scans. Noise was subjectively rated as best on the 70kEv images. SNR of the liver was highest on 70kEv images. SNR of the liver on 70kEv images was significantly better than SECT images (p < 0.0001). Liver CNR was highest on SECT (120kVp) images.

Conclusion: DECT with 50% reduction in the volume of intravenous contrast produces image quality comparable to that of SECT in cancer patients.