Quantitative Characterization of Dynamic Gadoxetic Acid–Enhanced Magnetic Resonance Imaging of the Liver and Kidneys in Healthy Dogs

초록

Background: Gadoxetic acid is a hepatocyte-specific contrast agent that also undergoes renal excretion, enabling simultaneous assessment of hepatic and renal function. Methods: This study quantitatively evaluated the enhancement patterns in the liver and kidneys using gadoxetic acid-enhanced dynamic magnetic resonance imaging (MRI) in healthy dogs to identify optimal imaging time points. Seven healthy Beagle dogs underwent dynamic MRI at 11 time points (pre-contrast to 120 minutes post-injection) following intravenous administration of gadoxetic acid (0.025 mmol/kg). Signal intensity (SI) was measured in six hepatic lobes and in the right renal cortex and medulla to calculate relative enhancement (RE). Time-intensity curves were analyzed to determine peak enhancement and time to peak (TTP). Results: Hepatic SI increased within 30 seconds, plateaued at 10 minutes, and remained stable until 60 minutes. Although TTP ranged from 20 to 40 minutes, no significant differences were noted, establishing 20 minutes as the optimal time for the hepatobiliary phase. In contrast, renal enhancement did not plateau, with TTP observed at 30 seconds in the cortex and 3 minutes in the medulla. Hepatic uptake and excretion were significantly slower than renal processes. Conclusion: Gadoxetic acid-enhanced dynamic MRI provides an effective means for quantitatively assessing both hepatic and renal enhancement in dogs. These findings establish 20 minutes as a practical optimal time point for hepatic evaluation and offer baseline reference data for clinical veterinary imaging.

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