title: Pseudoenhancement of simple renal cysts: a comparison of single and multidetector helical CT.
abstract: OBJECTIVE
  The purpose of this work was to compare the extent of pseudoenhancement (artifactual increase in measured attenuation of a simple cyst after contrast medium administration) in a phantom model on single detector and multidetector helical CT scanners.
  
  
  METHODS
  The phantom consisted of four water-filled spheres varying in size from 8 to 28 mm, suspended in an aqueous contrast medium bath. Iodine concentration in the bath was varied: 0, 6, 12, and 24 mg/ml corresponding to attenuation values of 0, +108, +180, and +300 HU. The phantom was scanned on single detector and multidetector helical CT scanners during the same session. Collimation (1, 3, and 5 mm) and pitch (1 and 1.5:1, single detector; 3:1 and 6:1, multidetector) were varied at each concentration. All scans were performed at 140 kVp and 170 mA. The region of interest was measured at the center of each sphere. The effects were analyzed using a linear regression model.
  
  
  RESULTS
  The degree of pseudoenhancement was more pronounced with increasing iodine concentration, decreasing cyst size, and wider collimation (all p = 0.0001). Pseudoenhancement was also more marked on the multidetector than the single detector scanner (p = 0.0001). At physiological levels of renal enhancement, the average pseudoenhancement was +18 HU for the single detector versus +23 HU for the multidetector scanner. Variation in pitch had no effect.
  
  
  CONCLUSIONS
  Pseudoenhancement is greater on a multidetector than a single detector helical CT scanner and may exceed 20 HU at physiological levels of renal enhancement.
authors.affiliation: Department of Radiology, Duke University Medical Center, Durham, NC 27710, USA. heneg002@mc.duke.edu
authors.forename: Joan P
authors.initials: JP
authors.lastname: Heneghan
authors.forename: Audrey L
authors.initials: AL
authors.lastname: Spielmann
authors.forename: Douglas H
authors.initials: DH
authors.lastname: Sheafor
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kliewer
authors.forename: David M
authors.initials: DM
authors.lastname: DeLong
authors.forename: Rendon C
authors.initials: RC
authors.lastname: Nelson
mesh_terms: D003287:Contrast Media; D006801:Humans; D007089:Image Enhancement; D052177:Kidney Diseases, Cystic / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media