Mapping tissue water T₁ in the liver using the MOLLI T₁ method in the presence of fat, iron and B₀ inhomogeneity

Modified Look‐Locker inversion recovery (MOLLI) T 1 mapping sequences can be useful in cardiac and liver tissue characterization, but determining underlying water T 1 is confounded by iron, fat and frequency offsets. This article proposes an algorithm that provides an independent water MOLLI T 1 (referred to as on‐resonance water T 1 ) that would have been measured if a subject had no fat and normal iron, and imaging had been done on resonance. Fifteen NiCl 2 ‐doped agar phantoms with different peanut oil concentrations and 30 adults with various liver diseases, nineteen (63.3%) with liver steatosis, were scanned at 3 T using the shortened MOLLI (shMOLLI) T 1 mapping, multiple‐echo spoiled gradient‐recalled echo and 1 H MR spectroscopy sequences. An algorithm based on Bloch equations was built in MATLAB, and water shMOLLI T 1 values of both phantoms and human participants were determined. The quality of the algorithm's result was assessed by Pearson's correlation coefficient between shMOLLI T 1 values and spectroscopically determined T 1 values of the water, and by linear regression analysis. Correlation between shMOLLI and spectroscopy‐based T 1 values increased, from r = 0.910 ( P < 0.001) to r = 0.998 ( P < 0.001) in phantoms and from r = 0.493 (for iron‐only correction; P = 0.005) to r = 0.771 (for iron, fat and off‐resonance correction; P < 0.001) in patients. Linear regression analysis revealed that the determined water shMOLLI T 1 values in patients were independent of fat and iron. It can be concluded that determination of on‐resonance water (sh)MOLLI T 1 independent of fat, iron and macroscopic field inhomogeneities was possible in phantoms and human subjects.