title: Threshold for Enhancement in Treated Hepatocellular Carcinoma on MDCT: Effect on Necrosis Quantification.
abstract: OBJECTIVE
  The objective of our study was to determine whether the conventionally used enhancement threshold of 10 HU for assessing tumor viability in treated hepatocellular carcinoma (HCC) lesions is valid.
  
  
  METHODS
  To distinguish pseudoenhancement from enhancement in a tumor, we used an in vivo model: The attenuation of 54 hepatic cysts during the unenhanced and portal venous phases of MDCT, similar to what may be observed in HCC with central necrosis, was used to determine the threshold for pseudoenhancement. To validate this model, we compared the attenuation value of liver parenchyma in this cohort with that of 22 HCCs during the late arterial phase of enhancement. We tested the effect of this pseudoenhancement on quantifying necrosis in HCC compared with the conventionally used threshold of 10 HU.
  
  
  RESULTS
  Values of enhancing HCC tissue on arterial phase MDCT (mean, 121.3 HU) were comparable with normal liver parenchyma on venous phase MDCT (117.3 HU) (p = 0.27). The threshold of 17.1 HU was the best threshold for the detection of pseudoenhancement in cysts (99% accuracy, 100% sensitivity, and 98% specificity). When this threshold was used instead of the conventional threshold of 10 HU, the mean necrosis proportion of treated HCC increased from 34.0% to 42.6% and the mean viable tumor proportion decreased from 66.0% to 57.4%. The quantification of viable HCC tissue based on 10 HU and the quantification of viable HCC tissue based on 17.1 HU were found to be significantly different (p < 0.0001).
  
  
  CONCLUSIONS
  The threshold of 17.1 HU may be the appropriate cutoff for nonenhancement in a necrotic HCC. Use of this threshold may potentially affect how response to therapy is quantified and categorized.
authors.affiliation: 1 All authors: Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Ste 800, Chicago, IL 60611.
authors.forename: Atilla
authors.initials: A
authors.lastname: Arslanoglu
authors.affiliation: 1 All authors: Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Ste 800, Chicago, IL 60611.
authors.forename: Hamid
authors.initials: H
authors.lastname: Chalian
authors.affiliation: 1 All authors: Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Ste 800, Chicago, IL 60611.
authors.forename: Faezeh
authors.initials: F
authors.lastname: Sodagari
authors.affiliation: 1 All authors: Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Ste 800, Chicago, IL 60611.
authors.forename: Adeel R
authors.initials: AR
authors.lastname: Seyal
authors.affiliation: 1 All authors: Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Ste 800, Chicago, IL 60611.
authors.forename: Hüseyin Gürkan
authors.initials: HG
authors.lastname: Töre
authors.affiliation: 1 All authors: Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Ste 800, Chicago, IL 60611.
authors.forename: Riad
authors.initials: R
authors.lastname: Salem
authors.affiliation: 1 All authors: Department of Radiology, Northwestern Memorial Hospital, Northwestern University Feinberg School of Medicine, 676 N Saint Clair St, Ste 800, Chicago, IL 60611.
authors.forename: Vahid
authors.initials: V
authors.lastname: Yaghmai
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy; D003560:Cysts / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000473:pathology*; D008107:Liver Diseases / Q000000981:diagnostic imaging / Q000473:pathology; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D061330:Multidetector Computed Tomography; D009336:Necrosis / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D014022:Tissue Survival
keywords: CT; Modified Response Evaluation Criteria in Solid Tumors (mRECIST); hepatocellular carcinoma; necrosis; viable