An Empirical Approach to Derive Water T1 from Multiparametric MR Images Using an Automated Pipeline and Comparison With Liver Stiffness

Abstract

Background: Water T₁ of the liver has been shown to be promising in discriminating the progressive forms of fatty liver diseases, inflammation, and fibrosis, yet proper correction for iron and lipid is required.

Purpose: To examine the feasibility of an empirical approach for iron and lipid correction when measuring imaging-based T₁ and to validate this approach by spectroscopy on in vivo data.

Study type: Retrospective.

Population: Next to mixed lipid-iron phantoms, individuals with different hepatic lipid content were investigated, including people with type 1 diabetes (N = 15, %female = 15.6, age = 43.5 ± 14.0), or type 2 diabetes mellitus (N = 21, %female = 28.9, age = 59.8 ± 9.7) and healthy volunteers (N = 9, %female = 11.1, age = 58.0 ± 8.1).

Field strength/sequences: 3 T, balanced steady-state free precession MOdified Look-Locker Inversion recovery (MOLLI), multi- and dual-echo gradient echo Dixon, gradient echo magnetic resonance elastography (MRE).

Assessment: T₁ values were measured in phantoms to determine the respective correction factors. The correction was tested in vivo and validated by proton magnetic resonance spectroscopy (¹ H-MRS). The quantification of liver T₁ based on automatic segmentation was compared to the T₁ values based on manual segmentation. The association of T₁ with MRE-derived liver stiffness was evaluated.

Statistical tests: Bland-Altman plots and intraclass correlation coefficients (ICCs) were used for MOLLI vs. ¹ H-MRS agreement and to compare liver T₁ values from automatic vs. manual segmentation. Pearson's r correlation coefficients for T₁ with hepatic lipids and liver stiffness were determined. A P-value of 0.05 was considered statistically significant.

Results: MOLLI T₁ values after correction were found in better agreement with the ¹ H-MRS-derived water T₁ (ICC = 0.60 [0.37; 0.76]) in comparison with the uncorrected T₁ values (ICC = 0.18 [-0.09; 0.44]). Automatic quantification yielded similar liver T₁ values (ICC = 0.9995 [0.9991; 0.9997]) as with manual segmentation. A significant correlation of T₁ with liver stiffness (r = 0.43 [0.11; 0.67]) was found. A marked and significant reduction in the correlation strength of T₁ with liver stiffness (r = 0.05 [-0.28; 0.38], P = 0.77) was found after correction for hepatic lipid content.

Data conclusion: Imaging-based correction factors enable accurate estimation of water T₁ in vivo.

Level of evidence: 1 TECHNICAL EFFICACY: Stage 1.

Keywords: liver fibrosis; liver inflammation; multiparametric MRI; water T1.