Comparison of modified two-point dixon and chemical shift encoded MRI water-fat separation methods for fetal fat quantification.

ABSTRACT

BACKGROUND: Fetal fat is indicative of the energy balance within the fetus, which may be disrupted in pregnancy complications such as fetal growth restriction, macrosomia, and gestational diabetes. Water-fat separated MRI is a technique sensitive to tissue lipid content, measured as fat fraction (FF), and can be used to accurately measure fat volumes. Modified two-point Dixon and chemical shift encoded MRI (CSE-MRI) are water-fat separated MRI techniques that could be applied to imaging of fetal fat. Modified two-point Dixon has biases present that are corrected in CSE-MRI which may contribute to differences in the fat measurements. PURPOSE: To compare the measurement of fetal fat volume and FF by modified two-point Dixon and CSE-MRI. STUDY TYPE Cross-sectional study for comparison of two MRI pulse sequences. POPULATION Twenty-one pregnant women with singleton pregnancies. FIELD STRENGTH/SEQUENCE 1.5T, modified two-point Dixon and CSE-MRI. ASSESSMENT Manual segmentation of total fetal fat volume and mean FF from modified 2-point Dixon and CSE-MRI FF images. STATISTICAL TESTS Reliability was assessed by calculating the intraclass correlation coefficient (ICC). Agreement was assessed using a one-sample t-test on the fat measurements difference values (modified two-point Dixon - CSE-MRI). The difference scores were tested against a value of 0, which would indicate that the measurements were identical. RESULTS: The fat volume and FF measured by modified two-point Dixon and CSE-MRI had excellent reliability, demonstrated by ICCs of 0.93 (P < 0.001) and 0.90 (P < 0.001), respectively. They were not in agreement, with CSE-MRI giving mean fat volumes 180 mL greater and mean FF 3.0% smaller than modified two-point Dixon. DATA CONCLUSION: The reliability between modified two-point Dixon and CSE-MRI indicates that either technique can be used to compare fetal fat measurements in different participants, but they are not in agreement possibly due to uncorrected biases in modified two-point Dixon. LEVEL OF EVIDENCE 4 Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2018.