title: Pseudostenosis in vessels adjacent to intracranial aneurysms on volume-rendered 3D angiograms: a phantom study.
abstract: OBJECTIVE
  Among artifacts on three-dimensional (3D) angiograms, pseudostenosis in vessels adjacent to intracranial aneurysms has not been described. By using a phantom, artifacts seen in vessels adjacent to intracranial aneurysms on volume-rendered 3D angiograms were assessed.
  
  
  METHODS
  Using a 3D angiography system and a C-arm sweep, digital images were obtained with a 512 x 512 matrix. Rotation was 30 degrees /second, and frame rate was 30 frames/second. Phantom aneurysms were designed to simulate intracranial saccular aneurysms and their parent arteries. Phantoms, consisting of a cylinder (inner diameter, 2 or 4 mm) and spheres, 10, 7, 5, 3, or 2 mm in diameter, were placed at 0 degrees and 45 degrees to the axis of rotation. Two radiologists consensually recorded their findings regarding the presence and location of stenosis and its relationship to the angle of rotation. The maximum percentage of stenosis in the pseudostenosis area was measured on multiplanar reconstruction images by using a workstation computer.
  
  
  RESULTS
  Pseudostenosis was observed in the cylinder adjacent to the sphere at both 0 degrees and 45 degrees angles; it was on a plane perpendicular to the axis of rotation. Pseudostenosis was most obvious with 10-mm spheres; it was not seen when spheres were 3 mm or less in diameter. The maximum percentage of stenosis of the pseudostenosis increased with sphere size.
  
  
  CONCLUSIONS
  On volume-rendered 3D angiograms, pseudostenosis was seen in the cylinder adjacent to the sphere. The artifact lay on a plane perpendicular to the axis of rotation, and sphere size affected the artifact.
authors.affiliation: Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto, 860-8556 Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamura
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hirai
authors.forename: Yukunori
authors.initials: Y
authors.lastname: Korogi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Ikushima
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Satoru
authors.initials: S
authors.lastname: Oishi
mesh_terms: D016477:Artifacts; D002533:Cerebral Angiography / Q000379:methods*; D002539:Cerebral Arterial Diseases / Q000000981:diagnostic imaging*; D003251:Constriction, Pathologic / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D012399:Rotation