title: Hepatic entropy and uniformity: additional parameters that can potentially increase the effectiveness of contrast enhancement during abdominal CT.
abstract: OBJECTIVE
  To determine how hepatic entropy and uniformity of computed tomography (CT) images of the liver change after the administration of contrast material and to assess whether these additional parameters are more sensitive to tumour-related changes in the liver than measurements of hepatic attenuation or perfusion.
  
  
  METHODS
  Hepatic attenuation, entropy, uniformity, and perfusion were measured using multi-phase CT following resection of colorectal cancer. Based on conventional CT and fluorodeoxyglucose positron emission tomography, 12 patients were classified as having no evidence of malignancy, eight with extra-hepatic tumours only, and eight with metastatic liver disease.
  
  
  RESULTS
  Hepatic attenuation and entropy increased after CM administration whereas uniformity decreased. Unlike hepatic attenuation, entropy and uniformity changed maximally in the arterial phase. No significant differences in hepatic perfusion or attenuation were found between patient groups, whereas arterial-phase entropy was lower (p=0.034) and arterial-phase uniformity was higher (p=0.034) in apparently disease-free areas of liver in patients with hepatic metastases compared with those with no metastases.
  
  
  CONCLUSIONS
  Temporal changes in hepatic entropy and uniformity differ from those for hepatic attenuation. By reflecting the distribution of hepatic enhancement, these additional parameters are more sensitive to tumour-related changes in the liver than measurements of hepatic attenuation or perfusion.
authors.affiliation: Department of Engineering & Design, University of Sussex, Brighton, UK. b.ganeshan@sussex.ac.uk
authors.forename: B
authors.initials: B
authors.lastname: Ganeshan
authors.forename: K A
authors.initials: KA
authors.lastname: Miles
authors.forename: R C D
authors.initials: RC
authors.lastname: Young
authors.forename: C R
authors.initials: CR
authors.lastname: Chatwin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms; D003287:Contrast Media; D019277:Entropy; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000592:standards; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000592:standards
chemical_list: D003287:Contrast Media