title: A meta analysis and hierarchical classification of HU-based atherosclerotic plaque characterization criteria.
abstract: BACKGROUND
  Many computed tomography (CT) studies have reported that lipid-rich, presumably rupture-prone atherosclerotic plaques can be characterized according to their Hounsfield Unit (HU) value. However, the published HU-based characterization criteria vary considerably. The present study aims to systematically analyze these values and empirically derive a hierarchical classification of the HU-based criteria which can be referred in clinical situation.
  
  
  METHODS
  A systematic search in PubMed and Embase for publications with HU-criteria to characterize lipid-rich and fibrous atherosclerotic plaques resulted in 36 publications, published between 1998 and 2011. The HU-criteria were systematically analyzed based on the characteristics of the reporting study. Significant differences between HU-criteria were checked using Student's t-test. Subsequently, a hierarchical classification of HU-criteria was developed based on the respective study characteristics.
  
  
  RESULTS
  No correlation was found between HU-criteria and the reported lumen contrast-enhancement. Significant differences were found for HU-criteria when pooled according to the respective study characteristics: examination type, vessel type, CT-vendor, detector-rows, voltage-setting, and collimation-width. The hierarchical classification resulted in 21 and 22 CT attenuation value categories, for lipid-rich and fibrous plaque, respectively. More than 50% of the hierarchically classified HU-criteria were significantly different.
  
  
  CONCLUSIONS
  In conclusion, variations in the reported CT attenuation values for lipid-rich and fibrous plaque are so large that generalized values are unreliable for clinical use. The proposed hierarchical classification can be used to determine reference CT attenuation values of lipid-rich and fibrous plaques for the local setting.
authors.affiliation: Department of Radiology, Center for Medical Imaging - North East, Netherlands, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Wisnumurti
authors.initials: W
authors.lastname: Kristanto
authors.forename: Peter M A
authors.initials: PM
authors.lastname: van Ooijen
authors.forename: Marijke C
authors.initials: MC
authors.lastname: Jansen-van der Weide
authors.forename: Rozemarijn
authors.initials: R
authors.lastname: Vliegenthart
authors.forename: Matthijs
authors.initials: M
authors.lastname: Oudkerk
mesh_terms: D006801:Humans; D008962:Models, Theoretical; D058226:Plaque, Atherosclerotic / Q000145:classification*
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