Gadoxetic Acid Uptake Rate as a Measure of Global and Regional Liver Function as Compared With Indocyanine Green Retention, Albumin-Bilirubin Score, and Portal Venous Perfusion

Abstract

PurposeGlobal and regional liver function assessments are important for defining the magnitude and spatial distribution of dose to preserve functional liver parenchyma and reduce incidence of hepatotoxicity from radiation therapy for intrahepatic cancer treatment. This individualized liver function-guided radiation therapy strategy is critical for patients with heterogeneous and poor liver function, often observed in cirrhotic patients treated for hepatocellular carcinoma. This study aimed to validate k1 as a measure of global and regional function through comparison with 2 well-regarded global function measures: indocyanine green retention (ICGR) and albumin-bilirubin (ALBI). Methods and MaterialsSeventy-nine dynamic gadoxetic acid enhanced magnetic resonance imaging scans were acquired in 40 patients with hepatocellular carcinoma in institutional review board approved prospective protocols. Portal venous perfusion (kpv) was quantified from gadoxetic acid enhanced magnetic resonance imaging using a dual-input 2-compartment model, and gadoxetic acid uptake rate (k1) was fitted using a linearized single-input 2-compartment model chosen for robust k1 estimation. Four image-derived measures of global liver function were tested: (1) mean k1 multiplied by liver volume (k1VL) (functional volume), (2) mean k1 multiplied by blood distribution volume (k1Vdis), (3) mean kpv, and (4) liver volume (VL). The measure's correlation with corresponding ICGR and ALBI tests was assessed using linear regression. Voxel-wise similarity between k1 and kpv was compared using Spearman ranked correlation. ResultsSignificant correlations (P < .05) with ICGR and ALBI were found for k1VL, k1Vdis, and VL (in order of strength), but not for mean kpv. The mean ranked correlation coefficient between k1 and kpv maps was 0.09. k1 and kpv maps were predominantly mismatched in patients with poor liver function. ConclusionsThe metric combining function and liver volume (k1VL) was a stronger measure of global liver function compared with perfusion or liver volume alone, especially in patients with poor liver function. Gadoxetic acid uptake rate is promising for both global and regional liver function.