Document Detail

Automatic classification of HITS into artifacts or solid or gaseous emboli by a wavelet representation combined with dual-gate TCD.
MedLine Citation:
PMID:  11739977     Owner:  NLM     Status:  MEDLINE    
BACKGROUND AND PURPOSE: Transcranial Doppler (TCD) can detect high-intensity transient signals (HITS) in the cerebral circulation. HITS may correspond to artifacts or solid or gaseous emboli. The aim of this study was to develop an offline automated Doppler system allowing the classification of HITS. METHODS: We studied 600 HITS in vivo, including 200 artifacts from normal subjects, 200 solid emboli from patients with symptomatic internal carotid artery stenosis, and 200 gaseous emboli in stroke patients with patent foramen ovale. The study was 2-fold, each part involving 300 HITS (100 of each type). The first 300 HITS (learning set) were used to construct an automated classification algorithm. The remaining 300 HITS (validation set) were used to check the validity of this algorithm. To classify HITS, we combined dual-gate TCD with a wavelet representation and compared it with the current "gold standard," the human experts. RESULTS: A combination of the peak frequency of HITS and the time delay makes it possible to separate artifacts from emboli. On the validation set, we achieved a sensitivity of 97%, a specificity of 98%, a positive predictive value (PPV) of 99%, and a negative predictive value (NPV) of 94%. To distinguish between solid and gaseous emboli, where positive refers now to the solid emboli, we used the peak frequency, the relative power, and the envelope symmetry of HITS. On the validation set, we achieved a sensitivity of 89%, a specificity of 86%, a conditional PPV of 89%, and a conditional NPV of 89%. CONCLUSIONS: An automated wavelet representation combined with dual-gate TCD can reliably reject artifacts from emboli. From a clinical standpoint, however, this approach has only a fair accuracy in differentiating between solid and gaseous emboli.
G Devuyst; G A Darbellay; J M Vesin; V Kemény; M Ritter; D W Droste; C Molina; J Serena; R Sztajzel; P Ruchat; C Lucchesi; G Dietler; E B Ringelstein; P A Despland; J Bogousslavsky
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Publication Detail:
Type:  Clinical Trial; Controlled Clinical Trial; Journal Article    
Journal Detail:
Title:  Stroke; a journal of cerebral circulation     Volume:  32     ISSN:  1524-4628     ISO Abbreviation:  Stroke     Publication Date:  2001 Dec 
Date Detail:
Created Date:  2001-12-13     Completed Date:  2002-01-25     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  0235266     Medline TA:  Stroke     Country:  United States    
Other Details:
Languages:  eng     Pagination:  2803-9     Citation Subset:  IM    
Department of Neurology, CHUV, the Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne, Geneva, Switzerland.
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MeSH Terms
Carotid Stenosis / complications
Heart Septal Defects, Atrial / complications
Intracranial Embolism / classification*,  complications,  diagnosis*
Middle Aged
Middle Cerebral Artery / ultrasonography
Predictive Value of Tests
Reproducibility of Results
Sensitivity and Specificity
Signal Processing, Computer-Assisted
Ultrasonography, Doppler, Transcranial / methods*

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