Meal-Induced Proton Density Fat Fraction and T 2 ∗ Decrease in Supraclavicular Adipose Tissue

Brown adipose tissue (BAT) is a metabolically active tissue in humans, located primarily within the supraclavicular adipose tissue (scAT), that can be activated by cold or high-caloric meal consumption. While the changes of proton density fat fraction (PDFF) upon cold activation are well investigated, there is a knowledge gap regarding PDFF and ${{\text{T}}_2}^{\ast }$ dynamics upon meal-induced BAT activation. Therefore, the purpose of this study was to establish a robust pipeline to quantify PDFF and ${{\text{T}}_2}^{\ast }$ changes in scAT in fasting control and meal intervention experiments. To that end, a motion-robust radial stack-of-stars trajectory has been employed with a regularized iterative reconstruction algorithm, graph-cut-based water-fat separation, affine image registration and automatic neural-network-based region of interest (ROI) segmentation. Next to scAT, ROIs of subcutaneous adipose tissue (SAT) and muscle have been created to compare the results to reference tissues. Multi-echo gradient echo acquisitions were repeated in a total of ten volunteers before a break, in which the volunteers consumed an iso-caloric meal in the meal intervention experiment. After the break, repeated multi-echo gradient echo measurements were used to dynamically track the changes of both PDFF and ${{\text{T}}_2}^{\ast }$ . In the meal intervention experiment, scAT PDFF showed a stronger decrease of $\sim 1{\%}_{\mathrm{PDFF}}$ compared to the fasting control experiment, in which the decrease below baseline was similar to that in SAT. Furthermore, scAT ${{\text{T}}_2}^{\ast }$ exhibited a strong decrease to $-3.2\text{ms}$ below baseline after meal intervention, while no decrease was observed in the fasting control experiment or in SAT. Considering the observed dynamic effects and their differences to the fasting control experiment, a PDFF decrease of $\sim 1{\%}_{\mathrm{PDFF}}$ and a ${{\text{T}}_2}^{\ast }$ decrease of $\sim 3\text{ms}$ could be attributed to meal-induced activation of scAT.