In Vivo K-edge Imaging on a Clinical Dual-source PCCT: Feasibility of Gadolinium Applications in a Porcine Model

Objectives

To evaluate the feasibility of in vivo gadolinium K-edge imaging on a clinical dual-source photon-counting CT (PCCT) system in a porcine model and to assess its performance for dynamic contrast-enhanced imaging, functional biliary imaging, and dual-contrast (bi-phasic) imaging.

Materials and Methods

A single healthy Yorkshire-Landrace pig was imaged on a clinical dual-source PCCT system (140 kVp; energy thresholds 20/55/72/90 keV; CTDI _vol 12 mGy). Gadolinium K-edge material-specific maps were generated with a calibration- based least-squares material decomposition. Three imaging protocols were evaluated for feasibility: (A) contrast dose testing for dynamic imaging with a hepatobiliary-clearing gadolinium contrast agent (0.2 and 0.8 mL/kg); (B) functional biliary imaging with dynamic and delayed acquisitions; and (C) dual-contrast imaging with simultaneous iodine and gadolinium decomposition. Attenuation (HU) and material concentrations (mg/mL) were measured from regions of interest.

Results

Gadolinium was quantifiable in material-specific maps at a contrast dose of 0.8 mL/kg (arterial aortic signal, 114 ± 4 HU and 1.4 ± 0.3 mg/mL; delayed bile duct, 111 ± 4 HU and 4.3 ± 0.4 mg/mL). Hepatobiliary excretion was tracked over time, with bile duct gadolinium plateauing near 3.3 mg/mL approximately 15 minutes after injection. In the dual-contrast acquisition, arterial gadolinium (2.5 ± 0.7 mg/mL) and portal venous iodine (1.9 ± 0.7 mg/mL) were separated within the liver, and both agents were separated within the ureters.

Conclusions

In this proof of concept, gadolinium K-edge imaging was feasible on a clinical dual-source PCCT system for dynamic, functional biliary, and dual-contrast applications, supporting further development with improved material-decomposition sensitivity and confirmation in larger studies.

Key Points

• Gadolinium K-edge imaging is feasible in vivo on a clinical dual-source photon- counting CT system, producing gadolinium-specific quantitative maps.

• Functional biliary imaging with gadoxetate disodium tracked hepatobiliary excretion over time, with biliary gadolinium plateauing approximately 15 minutes after injection.

• A dual-contrast acquisition separated gadolinium (arterial phase) from iodine (portal venous phase) within the liver and ureters, enabling simultaneous multi-phase, multi-agent imaging.