Quantitative Assessment of Pancreatic Fat by Using Unenhanced CT: Pathologic Correlation and Clinical Implications

Abstract

PURPOSE: To assess the relationship between computed tomographic (CT) indexes and histologically measured pancreatic fat in surgical specimens and to evaluate patients with impaired glucose metabolism in a clinical setting. MATERIALS AND METHODS: This retrospective study was institutional review board approved and informed consent was waived. The hospital database was searched for records from November 2008 to April 2009, and 62 patients (42 men and 20 women; mean age, 61.4 years; age range, 21-81 years) who underwent CT within 1 month before pancreatectomy were identified. The histologic pancreatic fat fraction (area ratio of fat to total tissue times 100%) was measured in nontumorous pancreatic tissue. Attenuation was measured in three regions of interest in the pancreas and the spleen on nonenhanced CT images. The difference between pancreatic and splenic attenuation and the pancreas-to-spleen attenuation ratio were calculated. Visceral fat area at the level of the umbilicus was measured on the CT images. Spearman correlation coefficients (ρ) were calculated to examine the correlation between the CT indexes or visceral fat area and the histologic pancreatic fat fraction. A multivariate logistic regression model was used to determine whether CT attenuation indexes and patient age, sex, and visceral fat correlated with impaired glucose metabolism (ie, impaired glucose tolerance, impaired fasting glucose, or presence of diabetes). RESULTS: The histologic pancreatic fat fraction ranged from 0% to 65.3% and was significantly correlated with the difference between pancreatic and splenic attenuation (ρ = -0.622, P < .01) and the pancreas-to-spleen attenuation ratio (ρ = -0.616, P < .01). The visceral fat area was not correlated with the histologic pancreatic fat fraction (ρ = 0.09, P = .50). The CT attenuation indexes were significant and independent variables predictive of impaired glucose metabolism after adjusting for age, sex, and visceral fat. CONCLUSION: Pancreatic fat can be quantified by using CT, and CT attenuation indexes that are applied to the quantification of pancreatic fat are significantly associated with clinical assessment of impaired glucose metabolism.