Noninvasive quantification of liver fat content by different gradient echo magnetic resonance imaging sequences in patients with nonalcoholic fatty liver disease

Background: Noninvasive quantification of liver fat by gradient echo (GRE) technique is aninteresting issue in quantitative magnetic resonance imaging. In this study, the fat content in patientswith nonalcoholic fatty liver disease (NAFLD) was quantified with GRE sequences with different T1 and T2* weighting. Methods: This prospective, cross-sectional study was performed on thirty NAFLD patients. Sixteen GRE sequences with different T1 weighting were performed with four echotimes. In each sequence, repetition time (TR) or flip angle was changed and other parameters werefixed. Forty-eight fat indexes (FIs) from 16 sequences were calculated based on three methods. Todetermine the relationship between FIs and histological findings, Pearson's correlation coefficient was used at the level of 1% significance. Results: Mean FIs which obtained from Eq. 3 have themaximum values in comparison to other FIs. The maximum FI was 23.58%, which related to heavily T1 weighted sequence obtained with method 3. The minimum FI was -2.49%, which related to theminimal T1 weighted obtained with method 2. FIs increase with a flip angle, especially at low flipangles. Increase the TR parameter decrease the FIs gradually. Calculated FIs with methods 1 and 3stronger correlated with histological findings relative to calculated FIs with method 2. Conclusion:For fat quantification, T1 relaxation effects probably more critical than T2*. Flip angle parametercould be a major factor causing the overestimation of liver fat content. Sequences with low flipangle are more suitable for fat quantification with methods 1 and 3. In fat quantification with GREtechniques, it is possible that the third and fourth echoes are unnecessary.