Automated measurement of liver attenuation to identify moderate-to-severe hepatic steatosis from chest CT scans

Purpose: Develop and validate an automated method for measuring liver attenuation in non-contrast low-dose chest CT (LDCT) scans and compare it to the standard manual method for identifying moderate-to-severe hepatic steatosis (HS). Method: The automated method identifies a region below the right lung within the liver and uses statistical sampling techniques to exclude non-liver parenchyma. The method was used to assess moderate-to-severe HS on two IRB-approved cohorts: 1) 24 patients with liver disease examined between 1/2013-1/2017 with non-contrast chest CT and abdominal MRI scans obtained within three months of liver biopsy, and 2) 319 lung screening participants with baseline LDCT performed between 8/2011-1/2017. Agreement between the manual and automated CT methods, the manual MRI method, and pathology for determining moderate-to-severe HS was assessed using Cohen's Kappa by applying a 40 HU threshold to the CT method and 17.4% fat fraction to MRI. Agreement between the manual and automated CT methods was assessed using the intraclass correlation coefficient (ICC). Variability was assessed using Bland-Altman limits of agreement (LoA). Results: In the first cohort, the manual and automated CT methods had almost perfect agreement (ICC = 0.97, kappa = 1.00) with LoA of - 7.6 to 4.7 HU. Both manual and automated CT methods had almost perfect agreement with (kappa = 0.90) and substantial agreement with pathology (kappa = 0.77). In the second cohort, the manual and automated CT methods had almost perfect agreement (ICC = 0.94, kappa = 0.87). LoA were -10.6 to 5.2 HU. Conclusion: Automated measurements of liver attenuation from LDCT scans can be used to identify moderate-tosevere HS on LDCT.