AT392358B - Method and equipment for examining the rheological relationships in a flow of a fluid medium containing particles - Google Patents

Abstract

The invention relates to a pulsed ultrasonic Doppler method and to equipment provided for carrying it out for examining the rheological relationships in a fluid flow 5 containing a large number of small particles, an average particle velocity being determined on the basis of the Doppler effect occurring during the back scatter of the sound from the particles. In order to obtain particularly effective information relating to particle agglomeration dependent on the degree of shear at precisely defined points in the flow 5, the invention provides that, in the evaluation, both a characteristic average frequency and a scattering factor are in each case determined or extracted, synchronously for the same volume region, from a number of Doppler frequency signal spectra each obtained from one and the same of the discrete volume regions of the particle flow 5, which are sampled step by step, and that, for each of the said volume regions, the average frequency obtained is used to determine an average velocity of the particles and, associated with this, the determined scattering factor is used in each case to determine the size and/or shape of the particles and/or particle aggregates in the same volume region, and that these mutually associated values are in each case fed to a storage and/or output unit 15 and are output by the latter, associated with one another, preferably in the form of particle-velocity and particle-size profiles. <IMAGE>

Description

AT 392 358 B

The invention relates to a method for, preferably non-contact, investigation of the rheological conditions in a stream of an at least two-phase, fluid medium containing a large number of particles, wherein ultrasound pulses of a predetermined frequency and duration are periodically sent into the fluid stream and the backscattered from the moving particles , due to Doppler effect with regard to their frequency, changed ultrasound echo pulses, preferably in the transmission pauses, received, converted into electrical reception signals, amplified and mixed with the signal on which the transmitted pulses are based, and the information thus formed relating to Doppler Signals containing frequency shift further predetermined largely after filtering out interfering frequencies with a number corresponding to a plurality of, preferably locally adjacent, discrete volume regions of at least part of a section transverse to the flow profile ner, step-wise changing time delays compared to the times of the beginning of the transmitted pulses, preferably sampled at times separated by the pulse length, and preferably after digitization, the Doppler frequency signals obtained for each of the time delays are converted into Doppler frequency signal spectra and these are stored and evaluated in a plurality of channels corresponding to the volume ranges or time delays mentioned, and finally the data received are output to a storage and / or output unit and output there, as well as devices for carrying out the method.

An essential object of the invention is to provide a method and a device for the quantitative detection or determination of the shear-rate-dependent structures in particle-containing fluid streams in situ, such as in particular in body fluid streams of humans and animals under conditions that are at least in vivo. The scattering of an incident ultrasonic wave on the particles or on structures formed by them, such as e.g. B. blood cell structures.

A low-contact or non-contact observation of the behavior of fine particles in flowing fluids is a major concern of experts in a wide variety of fields of technology and science and is becoming increasingly important, especially where there are interactions between the particles, e.g. B. can come to their aggregation. Every common material probe, which is to be placed in the most sensitive areas of a system through which the fluid flows, changes the flow conditions in such a way that often not even qualitative statements can be made about the fluid dynamics in these areas.

Areas of application for such investigations include the processing of ores, the processing of building materials, ceramics, pigments, paper, plastics, varnish and food, as well as waste water technology, where particle suspension flows occur everywhere are to be mastered, but also pharmaceutical production and medical technology including the diagnosis of flowing media in physiological systems.

In the medical sector, atraumatic, percutaneous blood flow measurements are of great importance in view of the increase in cardiovascular and vascular diseases and bring about a significant simplification of the diagnosis and »increased patient friendliness.

At the beginning of the development, attempts were made to determine the thixotropic properties and thus the dynamic by viscometric measurements, microscopic image evaluation or light scattering! Conclude structures of particle suspension »i. The latter method - equivalent to the ultrasound method developed later - can only be used to a limited extent as a result of strong absorption of the light waves, the inaccurate location of the measurement volume and complicated theoretical relationships between light scattering and fluid structure. In 1959, the so-called ultrasound Doppler procedure was used for vascular examination for the first time. This and the methods and devices derived from it are based on the so-called &quot; CW &quot; (continuous wave) Doppler method, in which an ultrasound beam is continuously sent into the particle stream to be examined and the ultrasound backscattered by the moving particles is received again by a receiver transducer. The received "echo" signal is compared to the Transmit signal frequency-shifted due to the Doppler effect, the difference frequency is displayed. An exact determination of the position of the location in the current where the speed is measured is not possible with this integral measuring method. Since the entire flow cross-section is not uniformly irradiated by the ultrasound beam, quantitative flow determination is also difficult

In order to obtain the location information which had not been accessible until then, &quot; pulsed ultrasonic Doppler methods &quot; developed in which short ultrasonic wave trains (bursts) are sent obliquely into the fluid flow, and the sound backscattered by the particles is received again. The location of the respective measurement location follows from the transit time of the ultrasound burst, i.e. from the time of reception of the "echo". As with the CW-Doppler-V, the information about the particle velocity is contained in the frequency shift of the received backscattered sound. If you set a specific reception time, i.e. a time at which the &quot; echo &quot; received, relative to the time of the beginning of the transmitted burst, the desired speed information is obtained from a single, discrete, small volume range at a specific point in the stream. This local position selectivity makes it possible to superimpose signals from -2-

AT392 358 B avoid the other areas of the current. Varying the times of reception - z. B. Gradually increasing delays in the reception times for locally adjacent volume ranges, that is to say "measuring depths", over the current cross section, a flow profile can be created. In order to achieve a high time resolution, multichannel ultrasound pulse Doppler speed measuring devices 5 are used to measure simultaneously simultaneously in a large number of the small volume ranges of the particle stream described. Devices operating in an analog manner have a plurality of Doppler signal evaluation units operating in parallel in order to determine the flow velocities in the individual measuring ranges of the particle flow. Digitization enables serial processing of the multi-channel stored signals corresponding to the volume ranges mentioned in different measuring depths. With knowledge of the respective 10 speeds at precisely known locations of a particle stream, in a line system, specific changes in the geometry or by means of measures that influence the fluid itself can cause particle aggregations, e.g. B. in places of lower shear where even a clogging of the flow cross-section can occur can be avoided. It is also known that in all vascular diseases, especially heart attack and its risk factors, the erythrocyte aggregation tendency and thus also the viscosity of the blood can increase sharply. This additionally pulsating, non-Newtonian liquid also shows visco-elastic effects, which can have an effect on every curvature, branching as well as narrowing or expansion of the circulation. As a result, there is a temporal phase shift between the measured flow and pressure. In addition, secondary flows are formed in front of constrictions, which increases the length of time for the corpuscles in such areas. Stationary vortices favor 20 an upstream growth of particle aggregations, such as. B. thrombi. The phenomena described also occur when moving technical particle suspensions, e.g. B. in polymer processing.

As a result of these phenomena, there is a clear or exact functional relationship between the actual flow velocity or shear rate profile and the type and extent of particle aggregations, e.g. B. size and shape of erythrocyte aggregates, which allows an estimation of the fluid dynamics 25 within a line section, not definable. Thus, even an exact determination of velocity profiles at critical points in a flow alone cannot be sufficient to effectively predict behavior and thus to effectively combat agglomeration tendencies of the moving particles.

The invention has set itself the task of overcoming the disadvantages of the previously known methods and 30 devices and to provide methods and devices which have non-reactive and non-invasively effective early detection, instantaneous detection as a function of location, quantification and countermeasures in systems Enable areas of difficult theological behavior. For rheology in physiological systems »! an essential improvement of diagnosis and treatment of vascular diseases is to be achieved. In general, direct in situ, e.g. B. in vivo analyzes 35 are obtained, which allow continuous observations, with which knowledge about aggregation in fluid streams can be kept under a variety of different conditions.

The invention thus relates to an examination method of the type mentioned at the outset, which is characterized in that when evaluating from the majority of the Doppler frequency 40 signal spectra obtained in each case from one and the same area of the step-wise sampled, discrete volume areas of the particle stream, both volume area synchronous both a characteristic, average frequency and a scattering factor are determined or extracted, and that, preferably on the basis of mathematical or calibration functions, an average velocity of the particles and assigned to them for each of the above-mentioned location volume ranges from the obtained average frequency are preferred on the basis of calibration functions, the size and / or shape of the 45 particles and / or particle aggregates located in the same volume range are determined from the scattering factor determined and that these respectively assigned values are fed to a storage and / or output unit rt and are assigned to each other, preferably in the form of particle velocity and particle size brofiles. It is a very essential feature of the invention that, for the purposes of obtaining the profiles of current velocity and particle dimen- sion from the series of volume regions transverse to the flow, the position of each one and the same small volume range defined in its local position 50 the mean frequency and the power of the backscattered sound which is correlated with the current particle size is made available as a result. The scattering factor describing the backscattering power is essentially greater the larger the particles are. The conversion of the values of the middle frequencies into speed values »advantageously follows on the basis of experimental studies, e.g. B. calibration functions obtained on defined particle streams and / or on the basis of the mathematical functions which can be derived from the Doppler effect itself. The acquisition of the data on the size of the particles and / or the formation of particle bonds can be carried out, since reproducible behavior is not exactly known, e.g. B. by means of calibration functions obtained using model tests. The &quot; scatter factor &quot; corresponds to the ratio of sound intensity backscattered by the particles in the stream per solid angle to the intensity of the ultrasound radiated into the particle stream. 60 A device according to the invention for carrying out the new method as described above is also particularly suitable for examining flowing physiological liquids, for example blood, and has a -3- controllable by means of a pulse supplied by a control (1) via lines (23).

AT 392 358 B

Transmitter (3) with oscillator (2) which can be fed via a switch (6) and which periodically emits ultrasound pulses of a predetermined frequency and duration, which can be directed obliquely into the fluid-medium stream (5) at a known angle and which is transferred from the particles into a » 'Ultrasound transducer (4), which receives back pulses scattered back to the fluid flow (5) and has a plurality of small volume regions of a cut, the above-mentioned switch (6) is an amplifier (7) adjoining it and having a line (21 ), (22) with the oscillator (2) connected mixer (8) for mixing the eidarian received signals of the converter (4) for flow direction »identification with two 90 ° phase-shifted basic oscillator signals, which in turn is connected via a filter» ( 9) for suppressing interfering frequencies with a unit (10), in particular analog-digital converter, which can be controlled by means of pulses supplied by the controller (1) via a line (25), for clocked sampling 10 of the double frequency Signals with adjustable time delays related to the respective start of the ultrasound pulses emitted by the transducer (4) are connected to which scanning unit (10) a device (11) is connected for storing the Doppler frequency signals in a multi-channel manner, which in turn has a device (12) for converting the "individual Doppl" difference signals into Doppler frequency signal spectra and a "device (13) for extracting the &quot; mean frequencies &quot; from the spectra, which is finally connected to an evaluation unit (14) for converting the extracted average frequencies into particle velocity values to a unit (15) for storing and outputting these values

The new device is characterized in that the said device (12) for generating the individual Doppler frequency signal spectra corresponding to the time cycle is connected to a device (13) which has a sub-device (131) for extracting the respective mean frequencies, which has a »20 its associated sub-device (132) for determining the scattering factor from the same Doppler frequency signal spectrum is connected to one another in essentially synchronous fashion, which sub-devices (131) and (132) are in turn assigned to each other via an evaluation unit (14) to a device (15) synchronous display of speed, speed gradient, degree and size of particles of the current, preferably in the form of current cross-sectional profiles, is connected 25 The invention enables for the first time a synoptic connection data specific to a location

Determination of the speed or the degree of shear within small volume ranges of a fluid stream containing moving particles with the values d »in the same discrete volume ranges and sizes or shapes of the u. a. Agglomerating particles depending on the shear rate, which is particularly important in the "number of cases where a prediction" no clear functional &quot; dependency &quot; can be used as a basis, such as in the area of curvatures, pumps, flow control elements, in agitators, fluidized beds or in the presence of non-Newtonian fluid suspensions, emulsions or dispersions as well as in physiological vascular systems.

For example, it enables the diagnosis of blood rheology in artificial kidneys. During the dialysis process platelets, erythrocytes hunt »! and leukocytes on the dialysis membrane 35. Also the high mechanical stress from a »deformation to the destruction of the erythrocytes by the

Blood pump can be quantified.

In the field of clinical precautionary and follow-up practice, knowledge and combating various »!» Disease patterns are optimized, such as: For example, in chronic arterial occlusive disease, the stage dependency, the behavior after administration of 40 vasoactive drugs, the behavior after vascular reconstructive interventions, e.g. B. Increased flow, reduction of shear force as well as detection and reduction of the risk of thrombosis, in diabetes mellitus the dependence of the blood flow on the degree, its dependence on the diabetes setting diabetic gangrene as well as the behavior after vasoactive medication; in the case of cerebrovascular insufficiency, the occurrence and therapy of carotid stenosis, intracerebral changes in the vessels and the intraoperative influence on hemodynamics; furthermore, in the case of venous thrombosis, the preoperative and intraoperative assessment and the very essential anticoagulant therapy.

Finally, the method according to the invention and the new device bring significant progress in the general testing of rheological medications, the examination of coronary sclerosis (heart attack), hemodilution, and hypercholesterolemia. The very specific increase in the binding force of an erythrocyte aggregation, which can be determined specifically in terms of the depth of the vessel, can clearly detect an impending intravascular thrombosis even at an early stage. Clinically applicable examination methods for this »important question have so far not become known. Because the greatest uncertainty about the course of development is in venous thrombosis, such as z. B. occur after surgical interventions without vein wall involvement. In these 55 cases, the coagulation status does not indicate any risk of thrombosis. Thus, pulmonary embolism is still a dreaded complication, which can only be influenced incompletely by therapy, such a thrombosis, which often ends in death. Therefore, the development of the investigation according to the invention »! represents a significant advance from a clinical point of view.

In many other areas of technology, however, the invention also enables the simultaneous detection of 60 associated with periodic or other changes in the speed profile of a particle-fluid stream simultaneously or with delayed particle aggregations during extremely short periods of time and in poorly accessible places of a fluid flowed through pipe system. It also enables moment-state- -4-

AT 392 358 B

Surveys that allow significant conclusions to be drawn about impending pressure-increasing constrictions or clogging, dangerous abrasions, the influence of additives to the fluid and the like. In addition to or at the same time with such short-term surveys, slowly occurring changes in flowing systems can be precisely observed over longer periods of time.

From the observations described, optimal conditions for guiding particle-fluid flows can finally be extracted from the geometric, fluid and control-technical point of view, and deficiencies in existing systems can be eliminated by appropriate influencing and countermeasures, such as e.g. B. Change da * flow rate or additives to the fluid slightly »* compensate.

Finally, the information obtainable according to the invention can be used to optimize the control of the rheology of particle-fluid flows at sensitive points in a fluid power system.

According to a preferred embodiment of the invention, it is provided that the conversion of the said Doppler frequency signals into the Doppler frequency signal spectra by means of high-speed (Fast) Fourier transformation (FFT) and the extraction of the mean frequencies of each of the individual volume ranges of the medium flow Cross-sectional signal spectra is made by means of signal processors on line. This ensures higher reliability and particularly high processing speed, which make it possible to disassemble even short-term flow processes with abrupt changes and to record the particle agglomerations that occur briefly, such as e.g. B. in due to pumping, kickback or resonance effect pulsating liquid flows or in pulsating blood in vivo.

In the sense of a more precise, more realistic description of the flow conditions, it has also proven to be advantageous to determine the mean frequencies on the basis of the formation of a quotient from the first and the zero moment of the Doppler frequency signal spectra.

To explain the term &quot; moment &quot; as it is to be understood here, the following is carried out: In probability theory, the &quot; first moment &quot; corresponds to the mean or expected value of a distribution function of a random variable, in the present case this &quot; random variable &quot; the Doppler frequency. Since the zero moment of a spectrum - or more precisely, of a power density spectrum does not have the dimensionless value 1, as in the case of a statistical probability distribution function, the first moment of such a spectrum must be related to the zero moment, i.e. the quotient of the first and zero moment are formed in order to obtain the mean again in the dimension of a frequency.

In order to achieve results that are as reproducible as possible and thus reflect the real conditions in particle-fluid flows, it is advantageous to in each case average values of the mean frequencies and / or scattering factors from a plurality of discrete volume ranges of the medium flow at the same individual times same phase position in pulsating flows (e.g. &quot; heartbeat synchronous &quot;) to determine the Doppler frequency signal spectra obtained and to base the calculation of the respective particle velocities and sizes. As a result, a large degree of independence from fluctuations in the flowing system and in particular individual measured values can be achieved. If, as provided in accordance with an advantageous variant of the invention, the mean frequencies and / or scattering factors determined in each case from the Doppler frequency signal spectra of each of the volume ranges of the medium flow detected by the sound beam by averaging from these named variables plus those from each locally, e.g. B. right and left, adjacent volume ranges originating and determined mean frequencies and / or scattering factors can be corrected, falsifications of results due to outliers and the like can be reduced.

A particularly accurate, because volume areas of very small extent, which detects sharper, synchronous determination of the speed and size of the particles of identical volume areas in each case can be achieved according to an embodiment which provides that ultrasound pulses periodically flow into the particle-containing flowing fluid medium to be examined continuously changing, preferably monotonically increasing or decreasing frequency and constant duration are sent and the electrical »received signals received by the backscattered ultrasonic pulses are subjected to a» pulse compression after their amplification. The technique of pulse compression is known from RADAR technology.

As far as preferred variations of the device according to the invention for rheology examinations of the type described, which have already been characterized in their basic elements, are concerned, it has proven to be particularly special with regard to the effects, which are often not yet clear for understanding, so far for understanding Advantageously, if the unit (12) for converting D Doppler frequency signals from the mixer (8) has at least one Fast Fourier processor

In the sense of simplified data transfer and processing, it is particularly advantageous if the above-mentioned devices for extracting the mean frequencies from the signal spectra and synchronously determining the scattering factors from identical spectra (131), (132) and for evaluation (14) as a computer Unit with algorithms for determining d »particle velocities occurring in the individual locally different volume ranges in the fluid stream (6) from the above-mentioned mean frequencies and for determining d» dimensions of the particles from the above-mentioned scattering factors which are dependent on the local position in the stream (5) is trained -5-

AT 392 358 B

According to a further preferred variant, which brings about an improvement in the accuracy of the determination of the speed gradients in the region of their steep rise, for example near the edge of the flow, and thus the degree of shear so important for particle agglomeration or agglomerate disintegration, units (13) and ( 14) for signal spectrum analysis and evaluation advantageously have an algorithm for refolding the particle speed profiles achievable according to the invention for improved spatial resolution of the degree of shear.

If, in a particularly preferred manner, the new device provides that its transmitter (3) has an expander for periodic delivery of ultrasound pulses of a predetermined duration and during this duration preferably a monotonically changing frequency and the amplifier (7) a compander for digital pulse Compression has, as is known per se from the RADAR technology, the above-mentioned advantages of higher accuracy of the results are further increased. With this embodiment variant, it is particularly advisable because of the surprisingly high reliability that the expander of the transmitter (3) and the compander of the amplifier (7) are formed by surface acoustic wave filters.

The invention will be explained in more detail with reference to the drawing, in which FIG. 1 shows schematically the structure of a device designed according to the invention and FIG. 2 shows an example of a synchronous output of the rheology data that can be achieved according to the invention:

1 shows an ultrasonic transducer (4) which is fed by an oscillator (2) and is excited by a transmitter (3) controlled by means of a control (1) via a line (23) by means of control pulses and supplied via a switch (6) at an angle between 0 and less than 90 ° to the course of the fluid stream (5) by means of pauses separate ultrasound bursts of a predetermined frequency and duration into which the fluid stream (5) containing the moving particles to be examined emits. A portion of the sound energy with the frequency changed as a result of the Doppler effect is scattered back from the particles in the fluid stream (5). Part of this is received by the ultrasound transducer (4) in the transmission pauses. The backscatter bursts received there are forwarded to an amplifier (7) via the switch (6) in the transmission pauses, after which the electrical signals thus obtained in the mixer (8) for flow direction detection with the lines (21) phase-shifted by 90 °, (22) supplied signals of the oscillator (2) are multiplied. After eliminating high-frequency mixed products by means of a low-pass filter (9), a signal is obtained for the duration of the received “echo” burst, which is mainly determined by the phase position of the receive burst relative to the mainly by the phase position of the receive burst relative to the phase position of the oscillator (2). This signal is generated by the scanning device (10) operating in the burst transmit clock, in particular an analog-digital converter with predetermined delays with respect to the start of the transmit pulse, corresponding to the respective local positions of the examined small volume ranges in the stream ("measuring depth"). Times sampled. Since in the fluid stream (5) an observed particle moves in a certain local position area of small extent at a certain speed, its distance from the ultrasound transducer (4) changes at this speed. This change in distance also means that the phase position of the received burst is relative to the oscillator ( 2) a different one for each transmission pulse. The analog-to-digital converter (10), which can also be supplied with control pulses by the controller (1) via line (25), delivers a different value at each sampling time. The pulses required to trigger the respective sampling are strictly synchronized by the controller (1) Frequency of the oscillator (2) connected to this controller (1) via a line (24) is generated. These clocked, sampled values form the information about the size of the Doppler frequency signals. Their frequency is equal to the Doppler frequency shift, which is experienced by a signal of the original frequency of the transmitter (3) reflected on a surface moved with the aforementioned speed of the particle of the current (5) under consideration. By determining the frequency of the Doppler frequency signals using mathematical functions such. B. Doppler relationship, speeds of the particles at the various points of the stream (5) can be calculated. In the multichannel ultrasound Doppler device shown, the aforementioned signals are sampled in the A / D converter (10) at very many times. With each of the above-mentioned delays in the scanning relative to the respective start of the transmission pulse, a Doppler frequency signal spectrum is basically measured with those frequency components which correspond to the flow velocities in the "measuring depths" of interest. in the fluid flow (5). In order to finally obtain speed profiles, that is to say courses of the speed over larger ranges of the measuring depths, the frequencies of all these Doppler frequency signals must be determined practically simultaneously. So that in addition to the amount, the direction of the speed can also be determined, mixing in the mixer (8) can also be done not only with the transmission signal. Mixer (8) and low-pass filter (9) form a quadrature demodulator that supplies two output signals that are phase-shifted by plus or minus 90 ° to one another. Depending on the sign of the phase shift, the speed of the particles in the stream (5) can be recognized as positive or negative. The shape and shape of the signals sensed by the scanning unit (10) are due to various factors, such as the spatial extent of the wall glass (4) and thus the localized volume range in the fluid stream (5), the finite duration of the bursts transmitted, the speed Differences since moving particles within the respective scanned volume range, transit time effects, turbulence, radial migration of the particles and reflections from possibly moving structures, e.g. B. vessel walls, and other noise mostly changed more. In the variant of the invention shown here, which has the great advantage of digital processability in a computer.

AT 392 358 B at high speed, they can also be considered. The sampled Doppler echo signals are stored in a device (11) for storage in a predetermined number of channels corresponding to the depth range of the particle stream (5) under consideration. From there, the wave trains with time abscissa are corresponding Doppler frequency signals of the individual channels a »- based on a 5 Fast Fourier processor, essentially corresponding to a signal spectrum analyzer, supplied device (12), where the conversion of the incoming Doppler frequency signals from every depth in the particle stream into corresponding Doppler frequency signal spectra takes place from these spectra in the part (131) of the unit (13) connected to the analyzer (12) an average (characteristic) frequency for each measuring depth-volume range, - which ultimately implicitly contains information about the particle speed in each depth position - and in the sub-device ( 132) essentially synchronous or par all for this purpose, for each of the identical volume ranges, a scattering factor corresponding to the power of the sound backscattered by the particles, which contains the information about the size and shape of the particles, is determined on the basis of corresponding computer programs. With the help of correction programs based on the corresponding mean frequencies and scattering factors, the IS can now use the locally defined volume range currently in the evaluation - e.g. B. right and left adjacent volume ranges falsified measurement results, z. B. &quot; Outliers &quot; be suppressed, which contributes to the smoothing of the profiles ultimately obtained. However, the results of a plurality of measurements corresponding to the two mutually identical, respectively identical measuring depths in the current (5) and determining data relating to the average frequency and scattering factor can also be averaged at times of the same phase position in periodic processes 20 (eg, heart rate synchronous The evaluation unit (14) can, in addition to the location-position range, synchronous evaluation and eventual averaging of average frequencies and scattering factors, particle velocity profiles of the current and exactly synchronous profiles, the dimensions of the particles or particle aggregates, or further, location-synchronous velocity gradients - i.e. shear degree profile as well statements about the current shape of the aggregating particles at very specific points in the stream 25 (5) can also be obtained, so that any changes in viscosity over the cross section of the stream can also be specified.

In each case both of the data streams determined in the evaluation unit (14) with the information about the speed and size of the particles are finally sent to a storage and output unit (15) suitable for the accumulation of data, e.g. B. Screen and / or printer passed on and made available by these 30 If necessary, they can also be fed to a process control unit.

The device shown was operated, for example, on a model flow with blood with a transmission frequency of 10 MHz, a burst length of 0.5 ps and a pulse repetition frequency of 15.6 kHz, 45 corresponding "measuring depths" areas corresponding to each other were used , obtained with 8 bit digitized short-term spectra. The clock frequency of the controller (1) was 32 MHz, a set of four TMS 32010 signal processors connected in parallel was used for the expansion (13), (14) 35.

Profiles of the blood particle speed and the position-dependent size of the cell structures in cross-section of the examined flow could be obtained every 16 ms in depth or volume range synchronous profiles and displayed on the screen of the output unit (15) and recorded by printing. This made it possible to obtain the complex theological processes in a certain section of the particle 40 stream with sufficient time resolution and meaningful accuracy.

A calibration and standardization of the device according to the invention can, for. B. by examining suspensions with polystyrene beads with a small diameter and known size distribution in water-glycerol mixtures at low volume concentrations.

FIG. 2 shows, on the basis of a schematic diagram based on a printer output with the 45 device according to the invention, assigned mutually associated profiles of the speed and particle size distribution proportional scattering factors over the cross section of a pipe with a 6 mm inner radius. In the diagrams (a), (b) and (c) the channels are on the abscissa starting from a wall each 0.375 mm deep, on the left ordinate the particle speed in mm / s, the shear rate in 1 / s and the 7 11

Scattering factor in 10 mm '^ sr, and on the right ordinate the aggregate size in factors times the 50 basic dimension 2 pm. The partial image (a) shows a non-unusual approximately parabolic fourth-order velocity distribution of the particles, the partial image (b) shows the degree of shear calculated therefrom and partial image (c) the scattering factor that changes with the particle size. Drawing (c) shows how the aggregate size decreases from the center of the flow to the first minimum. The state of the longitudinal position of the 55 erythtracytes in the area of the highest shear degree, which is manifested as a quasi-crystalline and which manifests itself as a brief rise in the curve, is clearly to be noted. -7- 60

Claims (12)

5 AT 392 358 B PATENT CLAIMS 1. Method for, preferably non-contact, examination of the theological conditions in a stream of at least two-phase fluid medium containing a large number of particles, whereby ultrasound pulses of predetermined frequency and duration are periodically sent into the fluid stream Ultrasonic echo pulses which are scattered back from the moving particles and changed in frequency as a result of the Doppler effect are converted into electrical reception signals, amplified, mixed with the signal on which the transmitted pulses are mixed, and the IS thus formed which contains the information about the Doppler frequency shift Signals with a number, corresponding to a number of discrete volumes preferably adjacent to one another locally, corresponding to at least part of a section transverse to the flow profile, with step-wise changing time delays with respect to the respective transmission pulse are then scanned, and the Doppler frequency signal spectra obtained for each of the time delays after conversion of the Doppler frequency signals are stored and evaluated in a plurality of channels corresponding to the discrete volume ranges or time delays 20 mentioned, and finally the data obtained a storage and / or output unit are delivered, characterized in that when evaluating from the majority of the Doppler frequency signal spectra obtained in each case from one and the same of the step-wise scanned, discrete volume ranges of the particle stream, a characteristic, average frequency is synchronized with the volume range as well as a scattering factor are determined or extracted, and that for each of the volume ranges mentioned, an average speed of the particles is assigned from the obtained mean frequency and this, the size and / or shape of the same in each case from the scattering factor determined Particles and / or particle aggregates located in the volume range are determined, and that these values assigned to each other are fed to a storage and / or output unit and are output from this unit, assigned to one another, preferably in the form of particle velocity and particle size profiles. 30th 2. The method according to claim 1, characterized in that the transfer of the Doppler frequency signals into the Doppler frequency signal spectra by means of high-speed (Fast) Fourier transformation (FFT) and the determination of the mean frequencies of each of the above, the individual volume ranges of the medium flow Cross-sectional signal spectra is made by means of signal processors on line. 35 3. The method according to claim 1 or 2, characterized in that the determination or extraction of the mean frequencies is in each case carried out on the basis of quotient formation from the first and zeroth moments of the Doppler frequency signal spectra. 4. The method according to any one of claims 1 to 3, characterized in that average values of the mean frequencies and scattering factors from a plurality of Doppler frequency signal spectra determined at the same individual discrete volume ranges of the medium flow at times of the same phase position in pulsating flows are determined and the combined Determination of the particle speed and size can be used as a basis. 45 5. The method according to any one of claims 1 to 4, characterized in that from the Doppler frequency signal spectra of each of the volume ranges of the medium flow detected by the sound beam each determined average frequencies and / or scattering factors by averaging from the sizes mentioned plus those from the respectively locally adjacent Volume ranges originating and determined mean frequencies and / or scattering factors 50 are corrected. 6. The method according to any one of claims 1 to 5, characterized in that periodically ultrasound pulses are transmitted in the particle-containing, flowing fluid medium to be examined, continuously changing, preferably monotonically increasing or decreasing frequency and constant duration and the 55 electrical reception Signals are subjected to pulse compression after their amplification. 7. Device for preferably non-contact examination of the rheological conditions in a stream of an at least two-phase, a plurality of particles-containing fluid medium, in particular flowing physiological liquids, for example blood, according to one of claims 1 to 6 with a 60 by means of the controller Transmitter-controlled transmitter with oscillator via a switch which can be fed, periodically emits ultrasound pulses of predetermined frequency and duration, can be directed obliquely into the fluid-medium flow at a known angle, and that of the particles in a plurality of -8 AT 392 358 B small volume areas of a section transversely to the fluid flow receiving ultrasound transducers, via the switch and an amplifier with a mixer connected via lines to the oscillator for mixing the electrical reception signals of the transducer for flow direction detection with two by 90 ° phase-shifted basic oscillator signals is connected, which in turn is controlled by a unit controllable by means of pulses supplied by the controller via a line, e.g. B. analog-digital converter, for clocked sampling because Doppler frequency signals with adjustable time delay related to the start of the ultrasound pulses emitted by the converter is connected to which scanning unit a device for multi-channel storage of the Doppler frequency signals is connected, which in turn is connected to a device for converting the individual Doppler frequency signals into Doppler frequency signal spectra and a device for extracting the respective mean frequencies from the spectra, which is finally sent to a unit via an evaluation unit for converting the extracted mean frequencies into particle velocity values is connected for the storage and / or output of this wedge, characterized in that the device (12) for creating the individual Doppler frequency signal spectra corresponding to the time cycle is connected to a device (13) which has a sub-device (131) for extracting the respective medium frequencies, which is connected to a sub-device (132) assigned to it for determining the scattering factor from the same Doppler frequency signal spectrum, which operates essentially synchronously, which sub-devices (131) and (132) in turn have an evaluation unit (14) is connected to a device (15) for synchronized storage and / or display of the speed and size of the particles of the stream (5), preferably in the form of profiles of these values over at least part of the flow cross-section 8. Device according to claim 6, characterized in that the device (12) for converting the Doppler frequency signals into the Doppler frequency signal spectra has at least one Fast Fourier processor. 9. Device according to claim 7 or 8, characterized in that the devices (13), (14), as a computer unit with algorithms for determining the particle velocities occurring in the individual locally different volume ranges in the fluid stream (5) from said medium frequencies and for determining the dimensions of the particles from the scattering cross sections mentioned, which are dependent on the local position in the stream (5). 10. Device according to one of claims 7 to 9, characterized in that the devices have an algorithm for refolding said speed profiles for improved spatial resolution of the degree of shear. 11. Device according to one of claims to 10, characterized in that the transmitter (3) an expander for the periodic delivery of ultrasonic pulses of a predetermined duration and during this duration, preferably monotonously, changing frequency and since amplifier (7) a compander digital pulse compression. 12. The device according to claim 11, characterized in that the expander of the transmitter (3) and the compander of the amplifier (7) are designed as surface acoustic wave filters. For this purpose 1 sheet of drawing