Quantification of Embolic Showers Using Radio-Frequency Based TCD Analysis

Lipperts, Matthijs; Sauren, Loes D C; Hoeks, Arnold P.G.; Mess, Werner H.

doi:10.1016/j.ultrasmedbio.2008.09.019

Cited by 9 publications

(12 citation statements)

References 12 publications

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“…Some authors recently proposed a radio-frequency based TCD analysis to overcome this limitation and better correlate the neurologic outcome to cerebral embolic load [10]. …”

Section: Discussionmentioning

confidence: 99%

Microembolic signals and strategy to prevent gas embolism during extracorporeal membrane oxygenation

Zanatta

Forti

Bosco

et al. 2010

J Cardiothorac Surg

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BackgroundExtracorporeal membrane oxygenation (ECMO) supplies systemic blood perfusion and gas exchange in patients with cardiopulmonary failure. The current literature lacks of papers reporting the possible risks of microembolism among the complications of this treatment.In this study we present our preliminary experience on brain blood flow velocity and emboli detection through the transcranial Doppler monitoring during ECMO.MethodsSix patients suffering of heart failure, four after cardiac surgery and two after cardiopulmonary resuscitation were treated with ECMO and submitted to transcranial doppler monitoring to accomplish the neurophysiological evaluation for coma.Four patients had a full extracorporeal flow supply while in the remaining two patients the support was maintained 50% in respect to normal demand.All patients had a bilateral transcranial brain blood flow monitoring for 15 minutes during the first clinical evaluation.ResultsMicroembolic signals were detected only in patients with the full extracorporeal blood flow supply due to air embolism.ConclusionsWe established that the microembolic load depends on gas embolism from the central venous lines and on the level of blood flow assistance.The gas microemboli that enter in the blood circulation and in the extracorporeal circuits are not removed by the membrane oxygenator filter.Maximum care is required in drugs and fluid infusion of this kind of patients as a possible source of microemboli. This harmful phenomenon may be overcome adding an air filter device to the intravenous catheters.

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“…Some authors recently proposed a radio-frequency based TCD analysis to overcome this limitation and better correlate the neurologic outcome to cerebral embolic load [10]. …”

Section: Discussionmentioning

confidence: 99%

Microembolic signals and strategy to prevent gas embolism during extracorporeal membrane oxygenation

Zanatta

Forti

Bosco

et al. 2010

J Cardiothorac Surg

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“…Several limitations of existing Doppler-based embolus detection methods have been reported in the literature. These include requiring computations that operate over large signal blocks, thereby limiting real-time operation [11], generation of excessive false positive events [8], and an inability to distinguish multiple emboli that flow through the insonation region simultaneously [18]. We have developed a novel singledepth, single-insonation-frequency embolus detection method that attempts to address these problems.…”

Section: Discussionmentioning

confidence: 99%

“…Embolus separation using TF analysis: Multiple emboli can often be generated simultaneously, such as during catheter manipulation during cardiac catheterization or aortic crossclamp release in cardiac surgery [8], [18]. Single-channel Doppler devices have been reported to be incapable of reliably detecting emboli in such circumstances [18]. Instead, methods have been proposed that use information from multiple depths (M-mode imaging) [40] or raw radio-frequency (RF) data [18].…”

Section: Discussionmentioning

confidence: 99%

“…Finally, multiple emboli may flow through the ultrasound sample volume simultaneously, and the corresponding Doppler signal should be decomposed into individual embolic signatures for accurate counting. Lipperts et al [18], for instance, reported that existing commercial TCD systems do not accurately estimate the number of cerebral emboli in such situations. To our knowledge, the problem of automatically separating signatures from multiple simultaneous emboli using single-depth, single-frequency TCD systems has not been addressed in the literature.…”

Section: Introductionmentioning

confidence: 99%

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A Time-Frequency Approach for Cerebral Embolic Load Monitoring

Imaduddin

LaRovere

Kussman

et al. 2020

IEEE Trans. Biomed. Eng.

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To enable reliable cerebral embolic load monitoring from high-intensity transient signals (HITS) recorded with single-channel transcranial Doppler (TCD) ultrasound. Methods: We propose a HITS detection and characterization method using a weighted-frequency Fourier linear combiner that estimates baseline Doppler signal power. An adaptive threshold is determined by examining the Doppler signal power variance about the baseline estimate, and HITS are extracted if their Doppler power exceeds this threshold. As signatures from multiple emboli may be superimposed, we analyze the detected HITS in the time-frequency (TF) domain to segment the signals into individual emboli. A logistic regression classification approach is employed to classify HITS into emboli or artifacts. Data were collected using a commercial TCD device with emboli-detection capabilities from twelve children undergoing mechanical circulatory support or cardiac catheterization. A subset of 696 HITS were reviewed, annotated, and split into training and testing sets for developing and evaluating the HITS classification algorithm. Results: The classifier yielded 98% and 96% sensitivity for 100% specificity on training and testing data, respectively. The TF approach decomposed 38% of candidate embolic signals into two or more embolic events that ultimately account for 69% of the overall embolic counts. Our processing pipeline resulted in highly accurate emboli identification and produced emboli counts that were lower (by a median of 64%) compared to the commercial ultrasound system's estimates. Significance: Using only single-channel, single-frequency Doppler ultrasound, the proposed method enables sensitive detection and segmentation of embolic signatures. Our approach paves the way towards accurate real-time cerebral emboli monitoring.

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“…To allow for better interpretation of different studies, we propose that researchers classify HITS as single, or occurring in clusters and curtains. Further refinement and validation of automatic emboli detection algorithms, as well as newer Doppler methods, such as radiofrequency-based TCD, 30 are necessary. A debate has been ongoing for decades about the etiology, composition, and clinical significance of HITS.…”

Section: Discussionmentioning

confidence: 99%