Automated whole-volume measurement of CT fat fraction of the pancreas: correlation with Dixon MR imaging

Objectives: This study aimed to assess the feasibility of pancreatic steatosis quantification by automated whole-volume measurement of the fat fraction of the pancreas on CT in comparison to MRI using proton-density fat fraction (PDFF) techniques. Methods: Fifty-nine patients who underwent both CT and MRI were analyzed. Automated whole-volume measurement of pancreatic fat on unenhanced CT was performed by a histogram analysis with local thresholding. Three sets of CT fat volume fraction (FVF) (%) values with thresholds of −30 Hounsfield unit (HU), −20 HU and −10 HU were compared to MR-FVF (%) values measured on a PDFF map. Results: The median −30 HU CT-FVF, −20 HU CT-FVF, −10 HU CT-FVF and MR-FVF values of the pancreas were 8.6% (interquartile range (IQR), 11.3), 10.5% (IQR, 13.2), 13.4% (IQR, 16.1) and 10.9% (IQR, 9.7), respectively. The −30 HU CT-FVF (%), −20 HU CT-FVF (%) and −10 HU CT-FVF (%) of the pancreas showed a significant positive correlation with the MR-FVF (%) of the pancreas (ρ = 0.898, p < 0.001, ρ = 0.905, p < 0.001, ρ = 0.909, p < 0.001, respectively). The −20 HU CT-FVF (%) displayed reasonable agreement with the MR-FVF (%) with a low absolute fixed bias (mean difference, 0.32%; limit of agreement from −10.1 to 10.7%). Conclusion: The automated whole-volume measurement of the CT fat fraction of the pancreas using the threshold CT attenuation value of −20 HU may be a feasible, non-invasive, and convenient technique for quantifying pancreatic steatosis. Advances in knowledge: CT-FVF value of the pancreas had a positive correlation with the MR-FVF value. The −20 HU CT-FVF may be a convenient technique for quantifying pancreatic steatosis.