title: Circle of Willis: evaluation with spiral CT angiography, MR angiography, and conventional angiography.
abstract: OBJECTIVE
  To evaluate the use of spiral computed tomographic (CT) angiography in the analysis of the arteries of the circle of Willis and compare these results with magnetic resonance (MR) angiography and conventional angiography.
  
  
  METHODS
  The results in 17 patients who underwent examination were prospectively studied in a blinded fashion. The presence or absence of the arteries of the circle of Willis was determined by using maximum intensity projection reconstructions from CT angiography and MR angiography. These results were compared with results from conventional angiography.
  
  
  RESULTS
  Similar sensitivities were determined for CT angiography (88.5%) and MR angiography (85.5%); however, MR angiography was found to differ significantly (P = .005) from conventional angiography. No significant differences (P > .05) were found between the two modalities and conventional angiography in the detection of the anterior, middle, or posterior cerebral arteries or the anterior communicating artery.
  
  
  CONCLUSIONS
  Spiral CT angiography is highly sensitive in the detection of arterial anatomy in the circle of Willis and is a reliable alternative to MR angiography.
authors.affiliation: Department of Radiology, Stanford University Medical Center, CA 94305-5105, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Katz
authors.forename: M P
authors.initials: MP
authors.lastname: Marks
authors.forename: S A
authors.initials: SA
authors.lastname: Napel
authors.forename: P M
authors.initials: PM
authors.lastname: Bracci
authors.forename: S L
authors.initials: SL
authors.lastname: Roberts
mesh_terms: D002533:Cerebral Angiography / Q000379:methods*; D002561:Cerebrovascular Disorders / Q000175:diagnosis / Q000000981:diagnostic imaging*; D002941:Circle of Willis / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D002537:Intracranial Arteriosclerosis / Q000175:diagnosis / Q000000981:diagnostic imaging*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D009072:Moyamoya Disease / Q000175:diagnosis / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*