Analysis of index modulation of doppler microembolic signals part II: in vitro discrimination.
نویسندگان
چکیده
The purpose of this study was to validate through experiments that frequency modulation (FM) of microembolic signatures was principally due to the radiation force. Several experiments were required to prove that such a frequency modulation originates from microdisplacements induced by the radiation force acting on microbubbles. The first experiment was performed to verify that the diffraction effects due to the presence of a skull did not disturb the acoustic field appreciably and to validate that a radiation force in the brain was sufficient to create a detectable microdisplacement. A second in vitro experiment using a single gate transcranial Doppler (TCD) system was conducted to show discrimination feasibility and to check that microembolic frequency modulation signatures (FMS) and frequency modulation index (FMI) were the same as those observed in vivo and those calculated by simulation. A final in vitro experiment was performed using a multigate multichannel TCD system to confirm the second experiment by directly measuring the microdisplacement induced by the radiation force. A new parameter, to be known as the position modulation index (PMI), is proposed. We showed that the radiation force is sufficient to induce detectable microdisplacements despite the presence of the skull. We also showed that the diffraction effects due to the skull induced a decrease in the ultrasound beam of 7.6 dB. Finally, we showed by using FMI and PMI that it is possible to discriminate gaseous from formed elements (<100 microns) despite the presence of the skull. The discrimination based on the FMI is an off-line technique allowing the analysis of standard TCD recordings. However, discrimination based on the PMI requires recordings obtained exclusively from a multi-gate system.
منابع مشابه
Analysis of index modulation in microembolic Doppler signals part I: radiation force as a new hypothesis-simulations.
The purpose of this study was to reveal the cause of frequency modulation (FM) present in microembolic Doppler ultrasound signals. This novel explanation should help the development of sensitive microembolus discrimination techniques. We suggest that the frequency modulation detected is caused by the ultrasonic radiation force (URF) acting directly on microemboli. The frequency modulation and t...
متن کاملTranscranial Doppler application for risk assessment of stroke in patients with mechanical mitral valve
Introduction: Observing microembolic signals in brain vessels by transcranial Doppler technology is a very common finding in patients with mechanical heart valve. These signals are almost always clinically asymptomatic. The aim of this study was assessment of transcranial Doppler in detecting probability of stroke in patients with mechanical heart valve. Methods: This descriptive study was ca...
متن کاملDoppler Microembolic Signals in Behcet\'s Disease with Nervous System Involvement
Background: Behçet’s disease (BD) is a multisystemic inflammatory vasculitis of unknown etiology, and vasculitis being its major pathological feature. Objectives: We studied the prevalence of microembolic signals (MES) in patients with diagnosis Behçet's disease. We also tried to determine the frequency of MES in BD patients with or without neurological involvement. Mater...
متن کاملHigh-resolution emboli detection and differentiation by characteristic postembolic spectral patterns.
BACKGROUND AND PURPOSE High-intensity transient signals (HITS) detected by transcranial Doppler ultrasonography correspond to microemboli in intracranial arteries. The purpose of this study was to develop new diagnostic criteria for the differentiation of these microembolic signals from artifact, based on a high-resolution analysis of Doppler power spectra in an in vitro model. METHODS Two hu...
متن کاملClopidogrel plus aspirin versus aspirin alone for reducing embolisation in patients with acute symptomatic cerebral or carotid artery stenosis (CLAIR study): a randomised, open-label, blinded-endpoint trial.
BACKGROUND Few randomised clinical trials have investigated the use of antithrombotic drugs for early secondary prevention of stroke or transient ischaemic attack in patients with intracranial atherosclerotic stenosis. Microembolic signals, detected by transcranial doppler, are a surrogate marker of future stroke risk and have been used to show treatment efficacy in patients with extracranial c...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Ultrasound in medicine & biology
دوره 37 1 شماره
صفحات -
تاریخ انتشار 2011