Impact of Clinical Environment on Embolus Detection: A Comparison of Automated and Manual Detection of Doppler Embolic Signals

Chung, Emma; Fan, Lingke; Naylor, A.R.; Evans, David H.

doi:10.1159/000097055

Cited by 8 publications

(9 citation statements)

References 24 publications

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“…This differs from previous studies, wherein embolus detection alone without differentiation was based on the opinion of observers, which may yield considerable variations in the number of emboli counted due to environmental changes and the obvious individual limits of the human auditory system. 17,18 Solid microemboli due to MHVs may consist of platelet aggregates or whole blood. Mechanical valve implants may induce platelet activation by increasing shear stress conditions.…”

Section: Discussionmentioning

confidence: 99%

Solid Cerebral Microemboli and Cerebrovascular Symptoms in Patients With Prosthetic Heart Valves

Skjelland

Michelsen

Brosstad

et al. 2008

Stroke

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Background and Purpose-Although cerebral microemboli are often detected by transcranial Doppler ultrasonography in mechanical heart valve patients, the clinical significance of such microemboli is unclear. The aim of this study was to determine the frequency and composition of cerebral microemboli in a prosthetic heart valve population and to correlate these findings to cerebrovascular symptoms, blood inflammation, and coagulation parameters. Methods-Seventy-six consecutive patients with a total of 81 prosthetic (54 mechanical, 27 biologic) heart valves were monitored for cerebral microemboli by multifrequency transcranial Doppler ultrasonography 1 year after valve replacement. Cerebrovascular events in the first year were recorded by a neurologist. Inflammation and coagulation markers were measured by immunoassays. Results-Microemboli were detected in mechanical heart valve patients only (28 patients, 56%). Twelve percent were solid, occurring in 17 (34%) of the mechanical heart valve population. The presence of solid cerebral microemboli was the only variable that was associated with cerebrovascular symptoms after a final regression analysis (Pϭ0.026). The plasma monocyte chemotactic protein-1 level was raised in patients with solid microemboli (Pϭ0.014). Conclusions-Solid cerebral microemboli were detected by multifrequency transcranial Doppler ultrasonography in 35% of a mechanical heart valve population, and the frequency was higher in patients who experienced cerebrovascular events during the first year after valve replacement. The results suggest that the detection of solid cerebral microemboli may be helpful in predicting the risk of ischemic stroke in mechanical heart valve patients.

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Section: Discussionmentioning

confidence: 99%

Solid Cerebral Microemboli and Cerebrovascular Symptoms in Patients With Prosthetic Heart Valves

Skjelland

Michelsen

Brosstad

et al. 2008

Stroke

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show abstract

“…Although human experts are currently considered the gold standard for embolus detection, they also have limitations when relying on their own human capacity to listen to emboli or artefacts and to look for transient intensity increases in the Doppler velocity display [14,15]. Low intensity emboli are particularly difficult to discriminate from the normal Doppler speckle and low velocity emboli might easily be confused with low frequency movement artefacts of short duration.…”

Section: Discussionmentioning

confidence: 99%

Introduction of an embolus detection system based on analysis of the transcranial Doppler audio-signal

Keunen

Hoogenboezem²,

Wijnands³

et al. 2008

Journal of Medical Engineering & Technology

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A new embolus detection system (EDS) is presented, built with the intention of detecting ongoing cerebral embolization in patients at risk of transient ischaemic attacks or stroke. It is based on the analysis of the audio-Doppler signal of a transcranial Doppler machine. The algorithm of the EDS estimates the intensity, duration and zero-crossing dynamics of the audio signal. The EDS has a multi-layer neural network which classifies events into micro-emboli signals (MES) or artefacts. The decision-making component of the software has been validated against human experts. Data from patients in the post-operative phase of carotid surgery were used for the validation process. The results showed agreement in MES and artefact classification of > 93%. Apart from a monitoring display, the monitoring system includes a verification unit that allows the user to listen and to look at all data of individual MES and artefacts. Moreover, the system allows the user to record, store and re-calculate all data files. Data are stored using European Data Format, which allows data transportation over the Internet. The EDS may have a potential in stroke risk stratification, evaluating the effect of novel anti-thrombotic therapies, and in peri-operative and remote monitoring of carotid endarterectomy.

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“…Large numbers of solid microemboli fall below the threshold for detection using conventional TCD. 7,8,23 Targeted bubbles could improve the sensitivity of TCD in detecting these small thrombus emboli.…”

Section: Discussionmentioning

confidence: 99%

“…It is estimated that around a third of emboli detected following carotid surgery produce Doppler embolic signal intensities that fall below the threshold for reliable detection. 7 Histological evidence suggests that TCD only detects a tiny fraction of emboli reaching the brain. In autopsy studies by Moody et al it was estimated that the brain received several million microemboli during cardiac surgery.…”

mentioning

confidence: 99%

Enhanced Detection of Thromboemboli With the Use of Targeted Microbubbles

Martín¹,

Chung²,

Goodall³

2008

Journal of Vascular Surgery

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assistance in obtaining the SEM images and specimen preparation respectively. Contributors listMatthew Martin carried out this study as part of his intercalated BSc project and took part in all aspects of the research. Emma Chung was responsible for routine supervision, study design and writing the paper. Alison Goodall supervised the preparation of thrombus samples. Alberto Della Martina created the microbubbles. Kumar Ramnarine supervised the flow-rig measurements. Lingke Fan wrote the software used for data collection and analysis.Sarah Hainsworth obtained the SEM images. A. Ross Naylor and David H. Evans were responsible for overall supervision. All authors have read and approved the final manuscript. Enhanced detection of thrombo-emboli using targeted microbubblesCover title: Microbubble enhanced thrombo-embolus detection Word count: 4051 words Abstract (222 words) Background and Purpose: Targeted ultrasound contrast agents have recently been developed to adhere selectively to specific pathogenic materials such as plaque or thrombus. Administration of such microbubbles has potential to aid transcranial Doppler ultrasound (TCD) detection of emboli, and to act as markers for distinguishing one embolic material from another. The purpose of this study was to investigate whether TCD detection of circulating thrombus emboli would be enhanced by the addition of targeted microbubbles. Methods: Binding of microbubbles to the surface of the thrombus was confirmed using Scanning Electron Microscopy. Targeted and control bubbles were then introduced to thrombus and tissue-mimicking material circulated under pulsatile flow conditions in an in vitro flow-rig. Embolic signal intensities before and after introduction of the bubbles were measured using transcranial Doppler ultrasound. Results: Targeted microbubbles enhanced Doppler signal intensities from thrombus emboli by up to 13 dB. The bubbles were capable of binding to moving thrombus when injected into the flow-circuit in low concentrations (~ 30 bubbles per 100 ml), and were retained on the thrombus under pulsatile-flow conditions. Signal intensities from similarly sized pieces of tissue mimicking material were not enhanced by injection of targeted bubbles.Conclusions: Injection of appropriately targeted microbubbles significantly enhances ultrasound detection of circulating thrombus emboli in vitro, and has potential to assist clinicians in distinguishing thrombus emboli from atheromatous plaque.

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Impact of Clinical Environment on Embolus Detection: A Comparison of Automated and Manual Detection of Doppler Embolic Signals

Cited by 8 publications

References 24 publications

Solid Cerebral Microemboli and Cerebrovascular Symptoms in Patients With Prosthetic Heart Valves

Solid Cerebral Microemboli and Cerebrovascular Symptoms in Patients With Prosthetic Heart Valves

Introduction of an embolus detection system based on analysis of the transcranial Doppler audio-signal

Enhanced Detection of Thromboemboli With the Use of Targeted Microbubbles

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