Mapping tissue water T in the liver using the MOLLI T method in the presence of fat, iron and B inhomogeneity.

Modified Look-Locker inversion recovery (MOLLI) T mapping sequences can be useful in cardiac and liver tissue characterization, but determining underlying water T is confounded by iron, fat and frequency offsets. This article proposes an algorithm that provides an independent water MOLLI T (referred to as on-resonance water T ) that would have been measured if a subject had no fat and normal iron, and imaging had been done on resonance. Fifteen NiCl -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 mapping, multiple-echo spoiled gradient-recalled echo and H MR spectroscopy sequences. An algorithm based on Bloch equations was built in MATLAB, and water shMOLLI T 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 values and spectroscopically determined T values of the water, and by linear regression analysis. Correlation between shMOLLI and spectroscopy-based T 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 values in patients were independent of fat and iron. It can be concluded that determination of on-resonance water (sh)MOLLI T independent of fat, iron and macroscopic field inhomogeneities was possible in phantoms and human subjects.