DE102004002227A1 - Ultrasound device for detection of emboli in patient arteries has an ultrasound sensor connected to an evaluation unit in which frequency differences between transmitted and received sound waves are processed to identify emboli - Google Patents

Abstract

Ultrasonic device for detection of an embolus comprises an ultrasound transceiver (1), an ultrasound probe that is connected to the transceiver, an arrangement for guiding the ultrasound probe into a section of a patient artery and an evaluation arrangement with which the frequencies of transmitted and received ultrasound waves are compared. From changes in the frequency, conclusions are made about the presence, number and movement speed of the emboli and are presented as the result of the examination. The invention also relates to a corresponding method for use with the inventive device.

Description

The The invention relates to a device and to a method for detecting embolisms in a fluid flow by means of a an ultrasound transducer connected to an ultrasound transmitter and receiver, wherein by means of the probe emitted ultrasonic waves and the of Moving objects caused reflections of these ultrasonic waves be received and evaluated.

devices and methods for detecting foreign bodies in a flowing fluid, in particular for the detection of embolisms in perfused blood vessels known from the medical field.

The previously established procedures for the detection of embolisms on the Doppler sonography, for example, the carotid artery ultrasound through the transtemporal bone window become. Disadvantageously, it is due to reflection, Absorption and scattering of ultrasound through the skullcap as well as due to confusion with other vessel sections, caused about through changes in location as a result of body movement, to disturbances and thus inaccurate detection results.

Around to remedy this, devices and methods have been developed which is measured simultaneously from two locations by means of ultrasound. Disadvantageously, this also does not guarantee that all embolisms detected because of the vessel ramifications including the blood the carried Particles in different body regions flows and therefore these particles no longer necessarily the measuring point happen.

For example, describes the DE 197 33 091 A1 a device and a method for embolic detection, in which an ultrasonic unit for receiving and Auswer tion of two reflected at different body position signal is set up and an embolus is signaled only if a characteristic change of the first or second signal outside a predetermined time interval of the other Signal enters.

One Another disadvantage of previous applications of Doppler sonography is the low penetration, which does not cause emboli in coronary vessels or inadequately ascertainable. Did you want the Doppler sonography to use for the detection of embolisms in coronary arteries, so that the Ultrasound signals that can penetrate the ribs of the thorax, very high ultrasound power with simultaneously very low ultrasonic frequency (about 2 MHz), resulting in poor resolution and This in turn would result in inaccurate results.

Especially in invasive procedures, such as PTCA (percutaneous transluminal coronary angioplasty), would an arranged on the chest ultrasound measuring device hinder the procedure, as the chest during the procedure in order Presentation of the vessels several times be x-rayed got to. Around The view or the picture should not be obscured, before each X-ray the measuring arrangement be removed, creating a continuous ultrasonic measurement not possible would.

One Another major disadvantage of the previous devices and Method is that with not parallel to the flow direction of the fluid emitted ultrasonic waves is measured. The ultrasonic waves are mostly from the outside directed perpendicular to the vessel section to be examined, resulting in Episode has that particle Swinging perpendicular to the ultrasound probe, therefore conditional by the Doppler principle no signal or at best a hardly measurable Provide signal and thus can not be detected.

The Therefore, currently known devices and methods are merely intended to detect emboli that are on their way to the brain and can lead to vascular occlusions there.

From that Based on the object of the invention, the efficiency to increase in the detection of embolisms and in particular the detection of emboli during a percutaneous coronary intervention already near her To allow the place of origin.

According to the invention Task solved with a device of the type described above, comprising a Ultrasonic transmitting and receiving device, an ultrasonic probe, which is connected to the ultrasound transmitting and receiving device is a device for insertion the ultrasound probe into an arterial vessel section of a patient and an evaluation device with which during a study period the frequencies of the received ones with the frequencies of the emitted ones Ultrasonic waves are compared, from frequency changes on the occurrence of embolisms is closed and their magnitudes, Number and / or movement speed determined and displayed as a detection result become.

A significant advantage over the up her known devices results in the inventive device inasmuch as the ultrasonic probe is no longer placed outside of the flowed through vessel portion, but in the flowing fluid and thereby the registration of artifacts or interfering signals is reduced to a minimum. Also, the detection of false signals coming from other than the vessel portion of interest, is avoided in this way. In addition, only a sensor for detecting the measured signals is needed so that reduce the technical and financial effort with the device according to the invention compared to the prior art.

to introduction the ultrasound probe into a vessel to be examined may have a Guide cannula used become. In the context of the invention, however, it is also the ultrasound probe through a multi-catheter to introduce the application yet other measuring devices is trained.

The The invention further relates to a method for detection of emboli by means of a connected to an ultrasound transmitting and receiving device Ultrasonic probe, in particular for operating the previously described Contraption.

According to the invention is provided that the Ultrasound probe in a vessel section introduced becomes, in which a fluid flows, by means of the in the vessel section positioned ultrasound probe emitted ultrasonic waves and that of flowing in the fluid Objects received reflections of the ultrasonic waves received and evaluated, the frequencies of the received with compared to the frequencies of the emitted ultrasonic waves, from frequency changes on the occurrence of embolism is closed and their magnitude, Number and / or movement speed determined and as a detection result being represented.

there the ultrasound probe is in the vessel section aligned so that the Ultrasonic waves are emitted parallel to the flow direction of the fluid. With the introduction the probe into the vessel section and the emission of the ultrasonic waves parallel to the flow direction becomes an extremely high accuracy achieved the embolic detection, since all objects or particles the Ultrasound probe must pass. Thus, the disadvantage of the prior art is repealed so far, when objects or embolisms no longer swim perpendicular to the ultrasound probe, no signal or too low a signal and therefore can go unnoticed.

A very particular embodiment of the method according to the invention is the ultrasound probe nearby of a possible Place of origin for To place emboli in. Thus, a method was found that it with the highest Security allows all while PCI (percutaneous coronary intervention) embolism to detect.

The Significance of this measure is above all that with the capture of emboli during this treatment, subsequent complications, e.g. arrhythmias, Microinfarcts, wall motion disorders and / or a reduced coronary reserve in the absence of atherosclerotic coronary occlusion can be countered. It also detects the emboli, transports the coronary vessels located distal to the treatment site and there are vascular occlusions with the Can cause episodes of infarction.

to Detection of analog ultrasonic signals according to the invention with a Ultrasonic frequency worked in the range around 15 MHz. The won Ultrasound signals are first digitized and then using wavelet scales of a signal analysis subjected to the occurrence of embolisms, contrary to Prior Art Method Using FFT (Fast Fourier Transformation) or shifted FFT (a time-frequency method using the FFT).

The Invention will be explained in more detail with reference to an embodiment.

• – eine Ultraschallsende- und -empfangseinrichtung 1, die mit einer Auswerteeinrichtung (zeichnerisch nicht dargestellt) gekoppelt ist;
• – eine Ultraschallsonde in Form eines Dopplerdrahtes 2 mit einem distalen, abstrahlungsseitigen Ende 3;
• – eine Führungskanüle 4, die zur Durchführung des Dopplerdrahtes 2 durch die Wandung eines arteriellen Gefäßes (zeichnerisch nicht dargestellt) dient;

The associated 1 shows by way of example the arrangement according to the invention, which essentially comprises:

• An ultrasound transmitting and receiving device 1 which is coupled to an evaluation device (not shown in the drawing);
• - An ultrasonic probe in the form of a Doppler wire 2 with a distal, radiation-side end 3 ;
• - a guide cannula 4 to carry out the Doppler wire 2 through the wall of an arterial vessel (not shown in the drawing);

The entry point 5 the guide cannula 4 in the arterial vessel is symbolically indicated by a reinforced double line.

In order to avoid complications due to embolisms during a PTCA or the treatment of a coronary occlusion, the guide cannula is used 4 the Doppler wire 2 with its radiation-side end 3 for example, introduced into the artery femoralis of a patient and into the coronary arteries or to the treatment site of the coronary occlusion advanced.

The radiation-side end 3 is positioned downstream of the treatment site as seen in the flow direction, and the ultrasonic waves are emitted in the direction of flow. This ensures that embolisms arising during the treatment are precisely detected, since these, like all other particles guided with the blood stream, end the radiation side 3 have to happen.

The evaluation device is a commercial ultrasonic Doppler device which, on the one hand, generates pulsed ultrasonic wave Doppler signals, which are transmitted via the Doppler wire 2 be sent out, and on the other hand also via the Doppler wire 2 returning from the comparison of the emitted and registered signals, the conclusions already drawn with regard to HITS (high intensity transient signals), which are caused by embolisms.

With this device it is possible from the acquired ultrasound signals not only the HITS and thus To select emboli, but also the blood flow velocity to determine. The HITS indicate that microemboli were present in usually formed from thrombus material or plaque particles can.

In already executed temptation analog measurement data initially were recorded with a key inserted into a coronary vessel Doppler wire was connected to an ultrasonic Doppler device "FloMap ^®", model 5500, manufacturers cardio Metrics Inc., USA.

The Doppler wire 2, which was pulsed with an output beam intensity of less than 720 mW / cm ² and an ultrasonic frequency of 15 MHz, was a 0.014 "standard design.

The analog measurement data were first with a matched to the ultrasound Doppler device sampling rate, here of 500 kHz, digitized. When choosing the sampling rate should be guaranteed be that particle speeds of up to 512 cm / s detected become. The sampling resolution should preferably be 12 bits.

A Single-channel digitization is conceivable, with a view to increased reliability the measurement results However, a two-channel digitization is recommended. In the concrete Case became with a first channel the real part and with a second channel the imaginary part of the ultrasonic signal digitized.

in the Connection to the digitization became a splitting of the now present Ultrasound signals using wavelet scales with consideration of the Frequency band made from 1 kHz to 30 kHz.

in the Connection with the ultrasonic Doppler device used here the signals of interest mainly in the frequency range of 5 kHz expected to 30 kHz, giving a particle velocity of 25 cm / s to 1 55 cm / s corresponds.

The now digitally present ultrasonic signals were in a next step after relevant events, i. after HITS, and after negligible, harmless events, the artifacts classified. For this was first to determine a threshold value. This should be more than twice that Intensity averaging of the analysis section for every single wavelet scale lies.

On this way, the HITS are up as signals with a duration of 8 ms 30 ms identifiable. Signals of shorter duration are called artifacts classified. Signals longer Duration is also not caused by HITS, but for example Persistent turbulence of the fluid in still narrowed vessels.

at the classification of the ultrasonic signals is assumed that the HITS above the flow speed the fluid in which they are carried, as the fast particles moving in fluid flow create turbulences behind them, the higher one Cause frequencies in the Doppler signal. The HITS extend always over several Wavelet scales, the flow velocities of 25 cm / s to 155 cm / s represent.

to Qualification of HITS will be first in the wavelet scales a temporal assignment to the heart rate taking into account, however, the heartbeat influence is what is done by threshold adjustment.

hereupon following, the signal power in the individual scales is determined, i. the scale total is formed and normalized to an average value. This Average value is in an embolism-free data record section, after two to three heartbeats a previous HITS, based on an adequate interval over several Milliseconds determined.

The HITS are in the Doppler frequency spectrum a high-intensity, short-term signal of the above duration, which is at least about 1 decibel above the background spectrum and of a typical musical noise with chirping character is accompanied.

1

ultrasonic transmitting and receiving device

2

Doppler wire

3

The End

4

guide cannula

5

of entry

Claims (8)

Apparatus for detecting emboli by means of ultrasound, comprising - an ultrasound transmitting and receiving device ( 1 ), An ultrasonic probe which is connected to the ultrasonic transmitting and receiving device ( 1 a device for introducing the ultrasound probe into an arterial vessel section of a patient, and an evaluation device with which the frequencies of the received ultrasound waves are compared during an examination period, from frequency changes to the occurrence of embolisms, and their magnitude, number and / or movement speed are determined and displayed as a detection result. Apparatus according to claim 1, characterized in that for introducing the ultrasound probe a guide cannula ( 4 ) is provided. Device according to claim 2, characterized in that that to introduction the ultrasound probe a multi-catheter is used, the application still other measuring devices is trained. Device according to one of claims 1 to 3, characterized that as Evaluation provided a commercial ultrasonic Doppler device is. Method for detecting embolisms by means of an ultrasound probe and receiver device ( 1 ), in particular for operating an arrangement according to claims 1 to 4, wherein - the ultrasound probe inserted into a fluid-conducting vessel, is advanced into the vessel to the vicinity of a place of origin of embolic and positioned there, - emitted by the ultrasonic probe ultrasonic waves and the reflections of these ultrasonic waves caused in the fluid are received and evaluated by - comparing the frequencies of the received with the frequencies of the emitted ultrasonic waves, from frequency changes on the occurrence of embolisms is closed and determines their magnitude, number and / or movement speed and displayed as a detection result. Method according to claim 5, characterized in that that the Ultrasonic waves emitted parallel to the flow direction of the fluid become. Method according to claim 5 or 6, characterized that the ultrasound probe - in an artery of a patient, preferably in the arteria femoralis, introduced becomes, - from over there the aorta into the coronary arteries to the treatment site of a coronary Closure is advanced, and - the determination of magnitude, Number and rate of movement of the emboli during the Treatment is carried out, the ultrasound probe in the flow direction is positioned behind the treatment site and the ultrasonic waves in the flow direction to be sent out. Method according to one of claims 5 to 7, characterized that - with the Ultrasound probe first Detects ultrasonic signals in the form of analogue measured data, - then digitized the measured data and then - the digitized Data from an assessment of the occurrence of emboli within filtered signal bands be subjected to wavelet scales.