title: Imaging of the internal carotid artery: the dilemma of total versus near total occlusion.
abstract: OBJECTIVE
  To evaluate ultrasonography (US) and magnetic resonance (MR) angiography in the differentiation between occlusion and near occlusion of internal carotid artery (ICA).
  
  
  METHODS
  Consecutive patients with occlusion or near occlusion of ICA at catheter angiography and who underwent MR angiography and US were included. MR angiography and US were compared with catheter angiography, the standard, for the ability to help distinguish occlusion from near occlusion. Noninvasive examinations were evaluated for the ability to classify near occlusions as having severe focal stenosis with distal luminal collapse versus diffuse nonfocal disease. The 95% CIs were calculated.
  
  
  RESULTS
  In 55 of 274 patients with 548 ICAs, catheter angiography depicted 37 total occlusions and 21 near occlusions. US depicted all total occlusions; MR angiography depicted 34 (92%) (95% CI: 0.78, 0.98). US depicted 18 (86%) of 21 (95% CI: 0.64, 0.97) near occlusions; MR angiography depicted all (100%). Of 18 vessels that were determined to be patent at US, 17 (94%) (95% CI: 0.73, 0.99) were classified as having focal stenosis or diffuse disease. Because flow gaps were identified in vessels with focal and diffuse disease, MR angiography was not effective in helping to differentiate these lesions.
  
  
  CONCLUSIONS
  Assuming US is the initial imaging examination, when occlusion is diagnosed, MR angiography can depict it. If occlusion is confirmed, no further imaging is necessary. US performed well in helping to differentiate vessels with focal severe stenosis from those with diffuse disease. MR angiography added little in this group. Catheter angiography remains beneficial for vessels with diffuse nonfocal narrowing.
authors.affiliation: Department of Radiology, West Los Angeles Veterans Administration Medical Center, 11301 Wilshire Blvd, Los Angeles, CA 90073, USA. sels@mednet.ucla.edu
authors.forename: S M
authors.initials: SM
authors.lastname: El-Saden
authors.forename: E G
authors.initials: EG
authors.lastname: Grant
authors.forename: G M
authors.initials: GM
authors.lastname: Hathout
authors.forename: P T
authors.initials: PT
authors.lastname: Zimmerman
authors.forename: S N
authors.initials: SN
authors.lastname: Cohen
authors.forename: J D
authors.initials: JD
authors.lastname: Baker
mesh_terms: D000368:Aged; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D016893:Carotid Stenosis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D012720:Severity of Illness Index; D014463:Ultrasonography