Comparing Quantitative T1 Mapping and Qualitative Functional Liver Imaging Score (FLIS) for Liver Functional Reserve Stratification: A Comparative Diagnostic Analysis.

RATIONALE AND OBJECTIVES: To compare the diagnostic performance of the qualitative Functional Liver Imaging Score (FLIS) and quantitative T1 mapping relaxometry in predicting clinical liver dysfunction (defined as ALBI Grade 2-3) and to propose a risk-stratified clinical imaging workflow. MATERIALS AND METHODS: This retrospective, single-center cohort study included 304 patients who underwent gadoxetic acid-enhanced magnetic resonance imaging. We performed an internal objective validation of visual FLIS subscores against quantitative hepatobiliary phase signal intensity ratios and T1 mapping data. The diagnostic performance of the total FLIS score and T1 reduction rate in predicting clinical liver dysfunction was evaluated using the receiver operating characteristic curve analysis and compared using DeLong's test. RESULTS: Excellent inter-reader agreement was observed for both total FLIS score (kappa = 0.88) and T1 reduction rate (intraclass correlation coefficient = 0.91). Visual FLIS subscores showed significant graded associations with the corresponding quantitative imaging metrics (all p < 0.001). The T1 reduction rate showed higher diagnostic performance for identifying Albumin-Bilirubin (ALBI)-defined liver dysfunction (area under the curve [AUC] = 0.86) than the total FLIS score (AUC = 0.81, p < 0.05). The T1 reduction rate achieved 84% sensitivity and 81% specificity at a cut-off of 54%. CONCLUSION: The FLIS components showed graded associations with the corresponding quantitative imaging measurements, while the T1 reduction rate demonstrated higher diagnostic performance than the total FLIS score for identifying ALBI-defined liver dysfunction in our cohort. These findings warrant prospective external evaluation of the potential complementary roles of FLIS and T1 mapping.