Reference Values for Water‐Specific T1 of the Liver at 3 T: T2*‐Compensation and the Confounding Effects of Fat

Abstract

BackgroundT1 mapping of the liver is confounded by the presence of fat. Multiparametric T1 mapping combines fat‐water separation with T1‐weighting to enable imaging of water‐specific T1 (T1Water), proton density fat fraction (PDFF), and T2* values. However, normative T1Water values in the liver and its dependence on age/sex is unknown.PurposeDetermine normative values for T1Water in the liver with comparison to MOLLI and evaluate a T2*‐compensation approach to reduce T1 variability.Study TypeProspective observational; phantoms.PopulationsOne hundred twenty‐four controls (56 male, 18–75 years), 50 patients at‐risk for liver disease (18 male, 30–76 years).Field Strength/Sequence2.89 T; Saturation‐recovery chemical‐shift encoded T1 Mapping (SR‐CSE); MOLLI.AssessmentSR‐CSE provided T1Water measurements, PDFF and T2* values in the liver across three slices in 6 seconds. These were compared with MOLLI T1 values. A new T2*‐compensation approach to reduce T1 variability was evaluated test/re‐test reproducibility.Statistical TestsLinear regression, ANCOVA, t‐test, Bland and Altman, intraclass correlation coefficient (ICC). P < 0.05 was considered statistically significant.ResultsLiver T1 values were significantly higher in healthy females (F) than males (M) for both SR‐CSE (F‐973 ± 78 msec, M‐930 ± 72 msec) and MOLLI (F‐802 ± 55 msec, M‐759 ± 69 msec). T1 values were negatively correlated with age, with similar sex‐ and age‐dependencies observed in T2*. The T2*‐compensation model reduced the variability of T1 values by half and removed sex‐ and age‐differences (SR‐CSE: F‐946 ± 36 msec, M‐941 ± 43 msec; MOLLI: F‐775 ± 35 msec, M‐770 ± 35 msec). At‐risk participants had elevated PDFF and T1 values, which became more distinct from the healthy cohort after T2*‐compensation. MOLLI systematically underestimated liver T1 values by ~170 msec with an additional positive T1‐bias from fat content (~11 msec/1% in PDFF). Reproducibility ICC values were ≥0.96 for all parameters.Data ConclusionLiver T1Water values were lower in males and decreased with age, as observed for SR‐CSE and MOLLI acquisitions. MOLLI underestimated liver T1 with an additional large positive fat‐modulated T1 bias. T2*‐compensation removed sex‐ and age‐dependence in liver T1, reduced the range of healthy values and increased T1 group differences between healthy and at‐risk groups.Evidence Level2Technical EfficacyStage 1