title: Diagnosis of fatty infiltration of the liver on contrast enhanced CT: limitations of liver-minus-spleen attenuation difference measurements.
abstract: BACKGROUND
  We investigated whether liver-minus-spleen (L-S) attenuation differences can accurately diagnose fatty infiltration of the liver on contrast-enhanced computed tomography (CT).
  
  
  METHODS
  A group of 78 patients administered a fast injection (90-s duration) of 150 mL 60% ionic contrast was compared with 81 patients given a slow injection (152.5 s). The presence or absence of fatty infiltration of the liver was diagnosed by noncontrast CT.
  
  
  RESULTS
  The L-S attenuation differences varied significantly, depending on both injection rate and timing of measurements. For the fast-injection group, the optimal L-S threshold for diagnosing fatty infiltration ranged from -43 to -33 Hounsfield units (HU) for early (79 s) and late measurements (106 s), respectively. For the slow-injection group, the optimal threshold ranged from -31 to -25 HU (80 and 112 s, respectively). In addition, sensitivity was not very high (range = 0.54-0.71) for either injection protocol at any measurement time because of significant overlap of L-S values between normal and fatty infiltration patients. Moderate and severe fatty infiltration were more reliably diagnosed than mild fatty infiltration by this method.
  
  
  CONCLUSIONS
  Contrast injection rate and timing of measurements significantly influence the optimal L-S threshold for diagnosing fatty liver. This limits the clinical usefulness of such measurements.
authors.affiliation: Department of Radiology, Veterans Affairs Medical Center, Denver, CO 80220, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Johnston
authors.forename: E R
authors.initials: ER
authors.lastname: Stamm
authors.forename: J M
authors.initials: JM
authors.lastname: Lewin
authors.forename: R E
authors.initials: RE
authors.lastname: Hendrick
authors.forename: P G
authors.initials: PG
authors.lastname: Archer
mesh_terms: D003287:Contrast Media / Q000008:administration & dosage*; D003973:Diatrizoate / Q000008:administration & dosage; D005234:Fatty Liver / Q000000981:diagnostic imaging*; D006801:Humans; D007262:Infusions, Intravenous; D007482:Iothalamate Meglumine / Q000008:administration & dosage; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013154:Spleen / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D003973:Diatrizoate; D007482:Iothalamate Meglumine