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Original research
Technical limitations of dual-energy CT in neuroradiology: 30-month institutional experience and review of literature
  1. Julien Dinkel1,2,
  2. Omid Khalilzadeh1,
  3. Catherine M Phan1,
  4. Ajit H Goenka1,
  5. Albert J Yoo1,
  6. Joshua A Hirsch1,
  7. Rajiv Gupta1
  1. 1Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
  2. 2Department of Radiology, University Hospital Heidelberg, Heidelberg, Germany
  1. Correspondence to Dr Julien Dinkel, Department of Radiology, University Hospital Heidelberg, Heidelberg 69120, Germany; julien.dinkel{at}med.uni-heidelberg.de

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.

Patients and 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.

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