Segment-resolved assessment of hydration effects on liver water-specific T1 in comparison with T1-MOLLI and transient elastography

Abstract

Background Quantitative liver T1 mapping is a promising noninvasive biomarker for diffuse liver disease, but it is influenced by physiological variability. Hydration alters tissue water content and perfusion, yet its effect on liver water-specific T1 (wT1) remains poorly characterized, particularly across liver segments. Prior studies relied on single-slice acquisitions, limiting assessment of spatial heterogeneity. The objective is to assess hydration-related changes in liver wT1 across all Couinaud segments using an accelerated multi-slice technique and to compare results with single-slice T1-modified Look-Locker inversion recovery (T1-MOLLI) and vibration-controlled transient elastography (VCTE). Methods Twenty-nine healthy adults underwent blood sampling, VCTE, and liver magnetic resonance imaging (MRI) after an ≥8-hour fast without fluid intake and again after ingestion of 1 L of water followed by a 1-hour equilibration period. Multi-slice wT1 mapping was performed using a Dixon-based continuous inversion-recovery Look-Locker (CIR-LL) sequence covering the entire liver in a single breath-hold. Single-slice T1-MOLLI and whole-liver proton density fat fraction (PDFF) and T2* mapping were acquired for comparison. Regions of interest (ROIs) were placed on PDFF, T2*, and wT1 maps in all liver segments. Statistical analysis included intraclass correlation coefficient (ICC; [2, 1]), linear regression, Pearson correlation coefficients Bland-Altman plots and paired two-sided t-tests. Results Hydration resulted in a higher global increase in mean liver wT1 (before: 773.4±63.2 ms, after: 800.3±66 ms) than T1-MOLLI (before: 853±68.8 ms, after: 861.6±55.9 ms). PDFF, T2*, and liver stiffness varied modestly within the physiological range. For liver stiffness, T1-MOLLI, and wT1, measurements obtained before and after hydration showed good agreement, with wT1 (y=0.9x+80.5, r=0.89, P<0.001) exhibiting a regression coefficient closer to that of liver stiffness (y=0.9x+0.7, r=0.63, P<0.001) than T1-MOLLI (y=0.6x+372.4, r=0.71, P<0.001). T1-MOLLI and wT1 showed good agreement under both hydration conditions (before: y=0.5x+355.7, r=0.64, after: y=0.8x+98.9, r=0.78), with T1-MOLLI yielding systematically higher values than wT1. Paired analysis demonstrated significant hydration-related changes in wT1 (P<0.001), with segment-wise wT1 increases remaining significant after correction for multiple testing. Furthermore, wT1 revealed spatial heterogeneity across liver segments. Conclusions Liver wT1 is physiologically modulated by hydration and exhibits spatial heterogeneity across liver segments, even in the healthy liver. These findings underscore the importance of whole-liver, segment-resolved wT1 mapping and physiological standardization when interpreting quantitative liver MRI.