Influence of fat on liver T1 measurements using modified Look–Locker inversion recovery (MOLLI) methods at 3T

Abstract

Purpose: To characterize the effect of fat on modified Look–Locker inversion recovery (MOLLI) T1 maps of the liver. The balanced steady-state free precession (bSSFP) sequence causes water and fat signals to have opposite phase when repetition time (TR) = 2.3 msec at 3T. In voxels that contain both fat and water, the MOLLI T1 measurement is influenced by the choice of TR. Materials and Methods: MOLLI T1 measurements of the liver were simulated using the Bloch equations while varying the hepatic lipid content (HLC). Phantom scans were performed on margarine phantoms, using both MOLLI and spin echo inversion recovery sequences. MOLLI T1 at 3T and HLC were determined in patients (n = 8) before and after bariatric surgery. Results: At 3T, with HLC in the 0–35% range, higher fat fraction values lead to longer MOLLI T1 values when TR = 2.3 msec. Patients were found to have higher MOLLI T1 at elevated HLC (T1 = 929 ± 97 msec) than at low HLC (T1 = 870 ± 44 msec). Conclusion: At 3T, MOLLI T1 values are affected by HLC, substantially changing MOLLI T1 in a clinically relevant range of fat content. J. Magn. Reson. Imaging 2016;44:105–111.