title: Anatomic evaluation of the circle of Willis: MR angiography versus intraarterial digital subtraction angiography.
abstract: OBJECTIVE
  To evaluate the reliability of source images and maximum intensity projection images of MR angiography in showing the arterial segments of the circle of Willis.
  
  
  METHODS
  In 62 patients, 526 arterial segments of the circle of Willis were determined to be present, partially present, or absent by blinded observers evaluating MR angiographic source images and maximum intensity projection images. Vessel diameter was measured on source images. These results were then compared with the results from intraarterial digital subtraction angiography.
  
  
  RESULTS
  MR angiographic maximum intensity projection images had a sensitivity of 87% and a specificity of 88% and MR angiographic source images had a sensitivity of 89% and a specificity of 63% in depicting the presence of a vessel segment. The positive predictive value of an arterial segment with a diameter of at least 1 mm was 99%.
  
  
  CONCLUSIONS
  MR angiography is a sensitive technique for detecting the anatomy of the circle of Willis. Maximum intensity projection images are more specific than source images. An arterial segment with a diameter of at least 1 mm on the source image is almost always present and patent.
authors.affiliation: Department of Radiology, University Hospital of Basel, Switzerland.
authors.forename: K W
authors.initials: KW
authors.lastname: Stock
authors.forename: S
authors.initials: S
authors.lastname: Wetzel
authors.forename: E
authors.initials: E
authors.lastname: Kirsch
authors.forename: G
authors.initials: G
authors.lastname: Bongartz
authors.forename: W
authors.initials: W
authors.lastname: Steinbrich
authors.forename: E W
authors.initials: EW
authors.lastname: Radue
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015901:Angiography, Digital Subtraction; D001157:Arterial Occlusive Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging; D001932:Brain Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging; D002941:Circle of Willis / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D006801:Humans; D007089:Image Enhancement; D002532:Intracranial Aneurysm / Q000175:diagnosis / Q000000981:diagnostic imaging; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis / Q000000981:diagnostic imaging; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011856:Radiographic Image Enhancement; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method