Quantifying Pancreatic Fat Using a Free‐Breathing Acquisition in Adults With Obesity Undergoing Diet‐Induced Weight Loss—Results From the LION Study

ABSTRACT

A free‐breathing six‐echo radial stack‐of‐stars acquisition is evaluated as an alternative to Cartesian breath‐hold scans for pancreatic fat quantification at 3T. Pancreatic fat deposition was assessed in 18 participants with obesity enrolled in a randomized controlled lifestyle intervention study (LION) using both a Cartesian breath‐hold scan and a free‐breathing high‐resolution stack‐of‐stars sequence (scan times: 16 s vs. 2 min 55 s). Pancreatic segmentations were initially generated using the VibeSegmentator and subsequently refined manually to reduce the amount of included visceral fat. The Intra‐observer reproducibility of the manual refinement was assessed after 3 months using Dice similarity score. SNR for both scan methods was quantified using a large water phantom. Mean segmented volume and mean pancreatic proton density fat fraction (PDFF) values between radial and Cartesian scans were compared. PDFF and volume changes between baseline and post‐intervention were investigated for both techniques. Segmented pancreatic volumes and PDFF measurements demonstrated excellent agreement between the radial and Cartesian sequences (Volume: R ²  = 0.97, ICC = 0.96; PDFF: R ²  = 0.98, ICC = 0.98). Compared to the Cartesian scans, the radial scans exhibited a minor positive volume bias at higher pancreatic volumes (linear regression: 0.85 x  + 9.4 cm ³ ; mean volume bias: 5.8 cm ³ , 95% LoA: −7.1 to 18.7 cm ³ ), alongside a proportional PDFF bias leading to slight overestimation at lower values and underestimation at higher values (linear regression: 0.88 x  + 2.1%; mean PDFF bias −0.2%, 95% LoA: −3.0 to 2.7%). Post‐intervention, both datasets captured significant decreases in pancreatic PDFF (mean loss 2.3% ± 2.1%, Cartesian p  < 0.001, radial p  < 0.01) and volume (mean loss 8.4 cm ³  ± 7.7 cm ³ ; both p  < 0.001). The present study demonstrates the feasibility of a free‐breathing radial stack‐of‐stars sequence for pancreatic fat quantification at 3T and its application in adults with obesity undergoing diet‐induced weight loss.