Dual-energy CT for TIPS patency assessment: quantitative iodine measurements and impact on diagnostic performance

OBJECTIVE: To compare diagnostic performance and reading time between standard portal-venous Dual-energy CT (DECT) images and additional material decomposition images (iodine maps and virtual non-contrast (VNC) images) for assessing transjugular intrahepatic portosystemic shunt (TIPS) patency, and to evaluate the diagnostic value of DECT-derived iodine measurements. METHODS: This retrospective single-center study included 57 consecutive patients with TIPS who underwent portal-venous DECT between November 2014 and July 2024. Five readers assessed standard portal-venous DECT images, and in a second session, additional material decomposition images for TIPS patency. Sensitivity and specificity between imaging sets were compared using McNemar's test across all reader-patient observations, reading time using the Wilcoxon signed-rank test. Iodine concentrations were measured in the inferior vena cava (IVC), portal vein, and TIPS using three regions of interest each. Receiver operating characteristic (ROC) analysis and Youden index determined optimal thresholds and diagnostic performance for absolute iodine concentration and iodine ratios (TIPS/portal vein, TIPS/IVC). RESULTS: Specificity was significantly higher with the material decomposition protocol than with the conventional protocol (98%, 95% CI: 95-100% vs. 93%, 95% CI: 88-96%; p < 0.001), while sensitivity did not differ significantly between protocols (91%, 95% CI: 82-97% vs. 97%, 95% CI: 90-100%; p = 0.219). Reading time decreased from 108 to 97 s (p < 0.001). Iodine concentration measurements achieved AUCs of 0.998 for absolute iodine concentration, 1.000 for the TIPS/portal vein ratio, and 0.995 for the TIPS/IVC ratio. Optimal thresholds (1.40 mg/mL, 0.262, 0.263) yielded sensitivities/specificities of 95%/100%, 100%/100%, and 98%/100%, respectively. CONCLUSION: Additional iodine maps and VNC images in DECT yield improved diagnostic performance in the visual assessment of TIPS patency. Iodine concentration measurements offer accurate, objective assessment of TIPS patency.