title: Variability of velocity and duration of microembolic signals detected by bigated transcranial Doppler sonography in carotid endarterectomy.
abstract: OBJECTIVE
  To differentiate between gaseous and particular microemboli in carotid surgery one clinical approach is the interpretation of the effective sample volume length (SVL). We investigated whether such a clinical interpretation is based on reproducible measurements.
  
  
  METHODS
  Microembolic signals (MES) recorded during carotid endarterectomy by a bigated transcranial Doppler device were analyzed off-line. In the two sample volumes, the duration and the velocity of the MES were measured by two observers independently from each other twice within 2 weeks. The SVL of the MES were calculated by multiplying duration with velocity.
  
  
  RESULTS
  In the anatomical proximal sample volume 215 MES were recorded of which 203 (94.5%) were also present in the distal. The SVL medians of the MES were 2.2-4.1 mm lower in the distal than in the proximal sample volume as a result of lower velocity and shorter duration of the MES in the distal sample volume. The median of the paired differences of the SVL was 0.2 mm (interquartile range: 0.0-1.2) in the proximal sample volume and 0.8 mm (0.2-1.8) in the distal sample volume for observer 1, and 0.6 mm (0.4-2.2) and 0.9 mm (0.5-1.6) for observer 2. The median of the paired differences of the SVL between the observers was 1.4 mm (1.2-2.9) in the proximal sample volume and 1.6 mm (1.3-3.0) in the distal.
  
  
  CONCLUSIONS
  The intra- and interobserver agreement on calculating SVL is good. However, the depth of insonation influences some features of embolic signals.
authors.affiliation: Department of Neurology, University Hospital of the Saarland, Oscar-Orth-Strasse 3, D-66421 Homburg/Saar, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Müller
authors.forename: X
authors.initials: X
authors.lastname: Pan
authors.forename: P
authors.initials: P
authors.lastname: Walter
authors.forename: K
authors.initials: K
authors.lastname: Schimrigk
mesh_terms: D000368:Aged; D002341:Carotid Artery Thrombosis / Q000000981:diagnostic imaging* / Q000601:surgery; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D016894:Endarterectomy, Carotid; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D015588:Observer Variation; D015203:Reproducibility of Results; D017585:Ultrasonography, Doppler, Transcranial; D014741:Video Recording