Abstract
Purpose Modified Look-Locker Inversion recovery (MOLLI) and Shortened MOLLI (ShMOLLI) T1 values can deviate substantially from the water T1 in voxels containing large amounts of water and fat. We introduce Water-Only Look-Locker Inversion recovery (WOLLI) to map water T1 in tissue containing fat.
Theory WOLLI comprises adiabatic water-selective inversion and several balanced steady-state free precession (bSSFP) readouts, followed immediately by adiabatic fat-selective inversion and bSSFP readout(s). Data are fitted pixel-wise and an adapted Deichmann-Haase saturation-correction gives the water T1.
Methods We compared two WOLLI protocols (WOLLI-w7f1 and WOLLI-w7f2f1), ShMOLLI and single-voxel spectroscopy at 3T in: simulations, fat/water phantoms, and 12 subjects’ livers.
Results In simulations with 0-40% fat fraction, T1 varied by: <0.5% (WOLLI-w7f1), <12% (WOLLI-w7f2f1), and >100% (MOLLI). In phantoms, the accuracy of the methods (i.e. worst-case T1w difference vs spectroscopy) was: WOLLI-w7f1 (best, maximum difference of 10.2%), WOLLI-w7f2f1 (max. 10.5%), and ShMOLLI (max. 81.5%). In the liver, the root-mean-squared deviations vs spectroscopy were: 374ms (WOLLI-w7f1), 645ms (WOLLI-w7f2f1), and 700ms (ShMOLLI).
Conclusion Compared to ShMOLLI, WOLLI is less influenced by fat, but more by B0-inhomogeneity. WOLLI was a clear improvement in phantoms but less so in vivo. WOLLI may be suited to scan organs with high fat content such as the liver.
Competing Interest Statement
The work described in this manuscript is the subject of US patent US10386429B2.
Footnotes
Aspects of this work were presented in a Power Pitch at the ISMRM2017 Annual Meeting (#0435). This method is subject of a US patent US10386429B2 with priority date 22 Apr 2016.