MRI measurement of pancreatic fat fraction based on Dixon method and correlation analysis with clinical factors

Objective To analyze the pancreatic fat fraction based on magnetic resonance Dixon sequence and correlation with clinical factors. Methods A total of 95 cases of adult physical examinees who had underwent abdominal MRI were retrospectively studied. Age, blood pressure, height and weight were recorded for every subject, and BMI was then calculated. The venous blood sample were analyzed for fasting plasma glucose (FPC), total cholesterol (TC), triglycerides (TG), low density lipoprotein-cholesterol (LDL-c) and high density lipoprotein-cholesterol (HDL-c). All cases underwent water-fat separation T1WI, fat inhibition T2WI, DWI, and coronal T2WI scans. We measured PFF of all the examinees, subcutaneous fat area (SA), visceral fat area (VA), and total abdominal fat area (TA) on the images above 8 centimeter of L4 to L5 were also measured, subcutaneous fat percentage (SFP) and visceral fat percentage (VFP) were further calculated. PFF of the 95 cases ranged from 2.1% to 35.0%, and the median PFF was 8.9%. This cohort was divided into low-fat pancreas groups (PFF≤8.9%, n=51) and high-fat pancreas group (PFF>8.9%, n=44) according to the median PFF. Independent sample t test was used to test for differences in clinical index between the two groups, Pearson correlation coefficient was used to measure the strength of a linear association between clinical indexes and PFF. Results Excellent water only, fat only, in phase and out of phase images of all the 95 adults were obtained. Signals of MRI images of all pancreas were homogeneous, the anatomic structures of all images were sharp and clear, and all the images had no motion artifact. The levels of BMI, systolic blood pressure, TG, LDL-c, FPC, VA, TA, VFP of high-fat pancreas group were significantly higher than those of low-fat pancreas group, and SFP was lower (P 0.05). PFF was weakly to moderately positively correlated with age, BMI, systolic blood pressure, diastolic blood pressure, TG, LDL-c, FPG, SA, VA, TA and VFP (r=0.219 to 0.515, P<0.05), SFP was moderately negatively correlated with PFF(r=-0.434, P<0.01). Conclusions It's feasible and accurate to measure the PFF with Dixon technique. PFF have a certain correlation with age, BMI, blood pressure, abdominal fat area and blood lipid metabolism. Key words: Pancreas; Magnetic resonance imaging; Fat fraction