title: Embolic Doppler ultrasound signal detection using continuous wavelet transform to detect multiple vascular emboli.
abstract: BACKGROUND
  Ischemic stroke is mainly caused by embolism. Vascular emboli can be solid or gaseous and can be non-invasively registered by transcranial Doppler ultrasound as microembolic signals (MESs). The existing methods are limited as they do not distinguish between cases in which a single embolus is present and those in which multiple emboli -- perhaps a mix of those gaseous and solid in nature -- are present. In a previous in vitro study, we have developed a wavelet-based algorithm to detect multiple emboli. We proceed with this technique to investigate whether it could prove useful in patients.
  
  
  METHODS
  MESs were collected during emboli monitoring from patients undergoing carotid artery stenting and from patients having middle cerebral artery stenosis, and continuous wavelet transform was used to detect multiple emboli.
  
  
  RESULTS
  From 17 MESs recorded from middle cerebral artery stenosis patients, we found no multiple MES. From 306 MESs recorded from carotid stenting, we found 31 multiple MESs.
  
  
  CONCLUSIONS
  Multiple emboli were detected and quantified in patients using continuous wavelet transform. These were difficult to observe using conventional analysis techniques.
authors.affiliation: Division of Neurology, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, China.
authors.forename: Him Shing
authors.initials: HS
authors.lastname: Ng
authors.forename: Qing
authors.initials: Q
authors.lastname: Hao
authors.forename: Thomas
authors.initials: T
authors.lastname: Leung
authors.forename: K S
authors.initials: KS
authors.lastname: Lawrence Wong
authors.forename: Hans
authors.initials: H
authors.lastname: Nygaard
authors.forename: J Michael
authors.initials: JM
authors.lastname: Hasenkam
authors.forename: Peter
authors.initials: P
authors.lastname: Johansen
mesh_terms: D000465:Algorithms; D016893:Carotid Stenosis / Q000000981:diagnostic imaging / Q000628:therapy; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D020244:Infarction, Middle Cerebral Artery / Q000000981:diagnostic imaging; D020766:Intracranial Embolism / Q000000981:diagnostic imaging*; D008991:Monitoring, Physiologic; D012680:Sensitivity and Specificity; D015607:Stents; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*