Regional differences in hepatic fat fractions in over- weight children and adolescents observed by 3T 1H-MR spectroscopy

Background : Proton MR Spectroscopy ( 1 H MRS) can be used to measure hepatic fat fractions (HFF) in liver cells for assessment of non-alcoholic fatty liver disease (NAFLD). The measurement is typically performed in a single volume. For correct diagnosis it is important to know variability of HFF within liver. The purpose of this study was to investigate regional differences in HFF in a large group of overweight and obese children and adolescents using 1H MRS at 3T. Methods: The study included 175 consecutive children and adolescents from 7 to 18 years old with a body mass index above the 97th percentile according to age and gender. 1 H MRS was performed at 3.0T using a point resolved spectroscopy sequence in two 11mmx11mmx11mm volumes positioned in different parts of the right liver lobe. Results: Up to 12% difference in HFF between the two volumes was observed: the regional differences in HFF are below 1% for patients with HFF under 3%; patients with HFF between 3% and 20% have regional differences in HFF up to 5%; patients with HFF over 20% have regional differences in HFF up to 12%. Conclusions: 1H MRS diagnosis and severity assessment of NAFLD in overweight and obese children and adolescents should take up to 12% regional differences in hepatic fat fractions into account.