title: Technical limitations of dual-energy CT in neuroradiology: 30-month institutional experience and review of literature.
abstract: BACKGROUND
  Dual-energy CT (DECT) has been shown to be a useful modality in neuroradiology.
  
  
  OBJECTIVE
  To assess failure modes and limitations of DECT in different neuroimaging applications.
  
  
  METHODS
  Dual-source DECT scans were performed in 72 patients over 30 months to differentiate contrast agent staining or extravasation from intracranial hemorrhage (ICH) (n=40); to differentiate calcium from ICH (n=2); for metal-artifact reduction (n=5); and for angiographic assessment (n=25). A three-material decomposition algorithm was used to obtain virtual non-contrast (VNC) and iodine (or calcium) overlay images. Images were analyzed in consensus by two board-certified radiologists to determine the success of the algorithm and to assess confounding factors. Furthermore, a dilution experiment using cylinders containing defined heparinized swine blood, normal saline, and selected iodine concentrations was conducted to assess other possible confounding factors.
  
  
  RESULTS
  Dual-energy analysis was successful in 65 (90.2%) patients. However, the algorithm failed when images were affected by beam hardening (n=3, 4.2%), the presence of a fourth material (parenchymal calcification) (n=3, 4.2%), or motion (n=1, 1.4%). In the dilution experiment, a saturation effect was seen at high iodine concentrations (≥37 mg/ml). VNC and iodine overlay images were not reliable above this concentration, and beam-hardening artifacts were noted.
  
  
  CONCLUSIONS
  DECT material decomposition is usually successful in neuroradiology. However, it can only distinguish up to three preselected materials. A fourth material such as parenchymal calcium may confound the analysis. Artifacts such as beam hardening, metallic streak, or saturation effect can also impair material decomposition.
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA Department of Radiology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Julien
authors.initials: J
authors.lastname: Dinkel
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Omid
authors.initials: O
authors.lastname: Khalilzadeh
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Phan
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Ajit H
authors.initials: AH
authors.lastname: Goenka
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Yoo
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Hirsch
authors.affiliation: Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Gupta
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D005260:Female; D006801:Humans; D020300:Intracranial Hemorrhages / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009485:Neuroradiography / Q000379:methods / Q000639:trends; D013525:Surgical Instruments; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000639:trends*
keywords: CT; Complication; Hemorrhage