title: Differences in Liver Imaging and Reporting Data System Categorization Between MRI and CT.
abstract: OBJECTIVE
  The purpose of this study is to determine whether focal liver observations are categorized differently by CT and MRI using the Liver Imaging and Reporting Data System (LI-RADS).
  
  
  METHODS
  We performed a retrospective review of 58 patients at risk for hepatocellular carcinoma who underwent liver protocol CT and MRI within 1 month of each other. Two readers assigned a LI-RADS category for all focal liver observations in consensus. A significant category upgrade was defined as a change from LI-RADS categories 1 and 2 or nonvisualization to LI-RADS categories 3-5, from LI-RADS category 3 to category 4 or 5, from LI-RADS category 4 to category 5, or from any category to LI-RADS category 5V. A significant downgrade was defined as a change from LI-RADS category 5 to categories 1-4, from LI-RADS category 4 to categories 1-3, or from LI-RADS category 3 to categories 1 or 2.
  
  
  RESULTS
  The LI-RADS category was different between CT and MRI for 77.2% (176/228) of observations. A significant upgrade occurred on MRI for 42.5% (97/228) of observations because of nonvisualization by CT (n = 78), capsule (n = 8), arterial hyperenhancement (n = 4), intratumoral fat (n = 2), larger size (n = 2), tumor in portal vein (n = 2), and wash-out (n = 1). Of these 97 upgraded observations, two were upgraded to LI-RADS category 5V, 15 were upgraded to category 5, and 13 were upgraded to category 4. A significant downgrade occurred on MRI for 8.8% (20/228) of observations because of marked T2 hyperintensity (n = 14), smaller size (n = 2), wedge shape (n = 2), and marked T2 hypointensity (n = 2).
  
  
  CONCLUSIONS
  LI-RADS categorization of focal liver observations is dependent on imaging modality. MRI results in both upgraded and downgraded categorization compared with CT in an important proportion of observations.
authors.affiliation: 1 Department of Radiology, University of California, Davis Medical Center, 4860 Y St, ACC Ste 3100, Sacramento, CA 95817.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Corwin
authors.affiliation: 1 Department of Radiology, University of California, Davis Medical Center, 4860 Y St, ACC Ste 3100, Sacramento, CA 95817.
authors.forename: Ghaneh
authors.initials: G
authors.lastname: Fananapazir
authors.affiliation: 1 Department of Radiology, University of California, Davis Medical Center, 4860 Y St, ACC Ste 3100, Sacramento, CA 95817.
authors.forename: Michael
authors.initials: M
authors.lastname: Jin
authors.affiliation: 1 Department of Radiology, University of California, Davis Medical Center, 4860 Y St, ACC Ste 3100, Sacramento, CA 95817.
authors.forename: Ramit
authors.initials: R
authors.lastname: Lamba
authors.affiliation: 2 Department of Radiology, Duke University Medical Center, Durham, NC.
authors.forename: Mustafa R
authors.initials: MR
authors.lastname: Bashir
mesh_terms: D000465:Algorithms; D006528:Carcinoma, Hepatocellular / Q000175:diagnosis*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000592:standards*; D008099:Liver / Q000473:pathology*; D008113:Liver Neoplasms / Q000145:classification / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging / Q000592:standards*; D012107:Research Design; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000592:standards*
keywords: CT; LI-RADS; MRI; hepatocellular carcinoma