Short‐Term Variability of Proton Density Fat Fraction in Pancreas and Liver Assessed by Multiecho Chemical‐Shift Encoding‐Based MRI at 3 T

Abstract

Background Quantification of pancreatic fat (PF) and intrahepatic lipids (IHL) is of increasing interest in subjects at risk for metabolic diseases. There is limited data available on short‐ and medium‐term variability of PF/IHL and on their dependence on nutritional status. Purpose To assess short‐term intraday variations of PF/IHL after a high‐fat meal as well as medium‐term changes after 5 days of high‐caloric diet. Study Type Prospective cohort study. Subjects A total of 12 subjects (six males) for intraday variations study, 15 male subjects for medium‐term high‐caloric diet study and 11 age‐ and body mass index (BMI)‐matched controls. Field Strength/Sequence A 3 T; chemical‐shift encoded multiecho gradient echo sequence. Assessment For the intraday study, subjects were scanned after overnight fasting and after a high fat meal on the same day. For the medium‐term study, 26 subjects were scanned after overnight fasting with 15/11 rescanned after 5 days of high‐calorie diet/isocaloric diet. Proton density fat fraction (PDFF) maps were generated inline on the scanner. Regions of interest were manually drawn in head, body, and tail of pancreas and in the liver by a medical physicist and a doctoral student (26/4 years of experience). PF was calculated as the average of the head, body, and tail measurements. Statistical Tests Repeated measurements ANOVA for assessing changes in PF/IHL, linear correlation analyses for assessing relationships of PF/IHL with BMI. Significance level P < 0.05 for all. Results Nonsignificant changes in PF (2.6 ± 1.0 vs. 2.7 ± 0.9% after high‐fat meal, 1.4 ± 0.8 vs. 1.5 ± 0.6% [high‐caloric diet] and 1.5 ± 0.8 vs. 1.8 ± 1.0% [isocaloric control group]), nonsignificant changes in IHL after high‐fat meal (2.6 ± 1.3 vs. 2.5 ± 0.9%) and in the control group (1.1 ± 0.6 vs. 1.2 ± 1.1%), significantly increased IHL after high‐caloric diet (1.7 ± 2.2% vs. 2.7 ± 3.6%). Nonsignificant changes in PF (2.6 ± 1.0 vs. 2.7 ± 0.9% after high‐fat meal, 1.4 ± 0.8 vs. 1.5 ± 0.6% [high‐caloric diet] and 1.5 ± 0.8 vs. 1.8 ± 1.0% [isocaloric control group]), nonsignificant changes in IHL after high‐fat meal (2.6 ± 1.3 vs. 2.5 ± 0.9%) and in the control group (1.1 ± 0.6 vs. 1.2 ± 1.1%), significantly increased IHL after 5‐days of high‐caloric diet (1.7 ± 2.2% vs. 2.7 ± 3.6%). Data Conclusion Time of day and nutritional status have no significant influence on PF/IHL and are therefore not likely to be major confounders in epidemiologic or clinical studies. Evidence Level 2 Technical Efficacy Stage 1

Eight weeks of empagliflozin does not affect pancreatic fat content and insulin secretion in people with prediabetes

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“…Recently, soy lecithin, a naturally occurring emulsifier that is mainly used in the food industry, has been identified as an attractive agent for the preparation of tissue‐like MRI fat–water phantoms 18,19 . In former experiments, it was found that dissolving small quantities of soy lecithin in aqueous solution does not lead to visible signals in spectra with a relatively short TE of 10 ms 18 …”

“…Recently, soy lecithin, a naturally occurring emulsifier that is mainly used in the food industry, has been identified as an attractive agent for the preparation of tissue-like MRI fat-water phantoms. 18,19 In former experiments, it was found that dissolving small quantities of soy lecithin in aqueous solution does not lead to visible signals in spectra with a relatively short TE of 10 ms. 18 Soy lecithin molecules are a class of phospholipids that, due to their amphiphilic nature, form self-assembled aggregates, so-called micelles, in aqueous solution. Depending on the concentration, temperature, and ionic environment, different shapes of aggregates such as bilayers or liposomes can form (Figure 1).…”