EP0789536A2 - Procede aux ultrasons et circuits permettant la mise en oeuvre de ce procede - Google Patents

Procede aux ultrasons et circuits permettant la mise en oeuvre de ce procede

Info

Publication number
EP0789536A2
EP0789536A2 EP95936497A EP95936497A EP0789536A2 EP 0789536 A2 EP0789536 A2 EP 0789536A2 EP 95936497 A EP95936497 A EP 95936497A EP 95936497 A EP95936497 A EP 95936497A EP 0789536 A2 EP0789536 A2 EP 0789536A2
Authority
EP
European Patent Office
Prior art keywords
ultrasound
ultrasonic
microbubbles
examination area
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP95936497A
Other languages
German (de)
English (en)
Inventor
Volkmar Dr. Uhlendorf
Christian Dr. Hoffmann
Thomas Dr. Fritzsch
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bayer Pharma AG
Original Assignee
Schering AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Schering AG filed Critical Schering AG
Publication of EP0789536A2 publication Critical patent/EP0789536A2/fr
Ceased legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/48—Diagnostic techniques
    • A61B8/481—Diagnostic techniques involving the use of contrast agent, e.g. microbubbles introduced into the bloodstream
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52023—Details of receivers
    • G01S7/52036—Details of receivers using analysis of echo signal for target characterisation
    • G01S7/52038—Details of receivers using analysis of echo signal for target characterisation involving non-linear properties of the propagation medium or of the reflective target

Definitions

  • the invention relates to ultrasound methods for imaging and optionally for evaluating a Doppler spectrum of objects with limited resistance to sound intensity, and to circuits for carrying out these methods.
  • ultrasound waves are radiated into an examination area for the selective imaging and / or evaluation of the Doppler spectrum.
  • Combined transmitter / receiver transducers are typically used in methods and devices for material testing and biological tissue testing. With the help of the crystals of the oscillators and the device electronics, a sound frequency (f 0 ) is determined, which is the same for sending and for receiving.
  • the reflected and / or backscattered signal is received in the same frequency range.
  • Such devices and methods are also used in the examination of biological tissues using ultrasound contrast agents.
  • EP-A2-0 147 955 describes an ultrasound method in which the object to be examined is exposed to a measurement pulse of high frequency and a pump pulse of low frequency but with a high sound pressure.
  • the pressure dependence on the speed of sound is used.
  • the pressure in the object to be examined is changed by the pump pulse.
  • the measuring pulse which is superimposed on the pump pulse, undergoes a phase change, which is ultimately used for the evaluation.
  • the important factor in this known method is therefore the phase relationship.
  • a method is known from EP-A3-0 072 330 in which the pressure in the object to be examined is measured.
  • bubbles are generated in the examined object only by exposing it to ultrasonic waves.
  • An ultrasound source of low frequency in the range from below about 100 MHz to typically about 20 MHz down generates vapor bubbles in gas-free liquids in the object to be examined in the low-pressure phase or, if dissolved gases are present, gas bubbles.
  • the ultrasound power is increased until cavitation bubbles form in the body to be examined.
  • Such bubbles can be very large (easily recognizable by the naked eye ⁇ bar) to remain in the sound field capture and create an embolism risk. If they are produced in the tissue, there are accompanying reactions such as those with pressure reduction complaints go along with expected. Because of the inevitable low frequency ultrasound scattering waves, there is a risk, particularly for lung damage.
  • EP-A2-0 068 399 describes a method for determining the ultrasound damping or absorption coefficient in the tissue. For this purpose, the change in the mean frequency of the backscattered spectrum over time or the spatial change therein is determined in the direction of progression. Because of the approximately frequency-proportional attenuation, the middle frequency shifts slowly towards lower frequencies as the distance of the ultrasonic energy pulse increases. The shift from f ⁇ to f c and f R is relatively small.
  • the blood pressure and the flow rate are measured.
  • individual bubbles of a controlled size are injected within a range of 10 to 100 ⁇ m in diameter and their resonance frequency is determined before and after the injection. This is done either with a damped transducer and a frequency sweep, or with shock excitation from a weakly damped transducer.
  • frequencies in the range from 60 to 600 kHz, i.e. with wavelengths from 2.5 to 25 mm must be used.
  • the bubbles used are large so that they cannot pass through the capillaries.
  • the speed of the bubbles is measured using the Doppler effect or determined from the time it takes to pass between two points.
  • the present method solves the problem.
  • These scattering and / or transmission signals are especially for the harmonics (2 f o , 3 f 7), the subharmonics (1/2 f o , 1/3 f o , 3/4 f Q ) and the superharmonics (2nd / 3 f Q , 5/4 f Q ...) of the excitation frequency intense.
  • low frequencies can be irradiated, so that a greater depth of penetration is achieved, and received signals of higher frequency can be evaluated.
  • the selective evaluation of the signal components influenced by the materials or media that have been introduced and the selective representation of these areas filled with these means are advantageously possible without - as was previously required - to find the difference between two or more conditions that were registered before and after the introduction of the materials or media.
  • the Doppler effect that has been generated can be evaluated free of artifacts.
  • nonlinear scattering bodies are introduced into the examination area, but nonlinear ultrasound contrast media in the form of a solution or suspension and especially microbubbles or agents that produce microbubbles can also be introduced into the examination area.
  • Suitable nonlinear ultrasound contrast agents are, for example, the agents described in EP 0 365 457, which are incorporated by reference into the disclosure and which are based on galactose particles which contain fatty acid.
  • contrast agents as are described in DE 38 03 972, WO 93/25242 and WO 94/07539 and which are introduced here by reference can also be used.
  • These agents contain microparticles that consist of a gas core and a polymer shell and show an ambivalent behavior. At low sound pressure they show a behavior with linear scatter, at higher ones
  • microbubble suspension having a concentration of 10 ⁇ 3 wt% to 30 wt% dry matter in the suspension medium gives good results.
  • the method according to the invention and the circuit according to the invention surprisingly reach the low lower limit of 10 "3 % by weight.
  • Sensitivity possible show a disproportionate increase in the level of the temporary backscatter signals with an increase in the amplitude of the emitted signal above a certain threshold.
  • This disproportionate level increase can occur not only at the frequency of the emitted signal (f 0 ), but especially at 1/2 f Q , 3/2 f Q , 2 f 0 , 5/2 f o , 3 f 0 , 7/2 f o and 4 f 0 can be observed. Since the backscatter signal at 2 f almost reaches the intensity of f 0 when the excitation is above the threshold value, that signal is preferably detected. Detection of individual particles or gas bubbles is possible due to excitation in the diagnostic range that is above the threshold value.
  • the dose required for space-filling contrasting can be reduced in the area examined to a particle concentration (gas bubble concentration) of 10 ppb. If the relative density of 1 ppb is taken into account, this concentration corresponds to about 1000 particles, preferably 100 to 1000 particles, per cm 3 of the examined body area. Concentrations of 1000 to 100,000 particles per cm 3 can also be used.
  • the reduction in the contrast agent concentration results in a reduction in the acoustic damping which is caused by the contrast medium, as a result of which the penetration depth of the irradiated ultrasound signal into the tissue is increased. Sonographic examination of the lower parts of the body is also possible.
  • the irradiation of ultrasound with an energy above the threshold value causes the particles to be destroyed (or the gas bubbles to burst), so that the concentration of the particles (bubbles) in the tissue is constant over the course of the examination decreases.
  • the particles (bubbles) that are closest to the sound source are destroyed first.
  • the ultrasound signal also penetrates to the layers below it, which enables uniform contrast formation through all tissue layers (organ layers). Because these processes, especially in the areas of the smallest contrast medium concentration, take place in very short periods of time run, the recording of the received signals by modern data acquisition storage techniques is particularly preferred.
  • the energy required to destroy the particles (bubbles) changes as a function of the contrast medium selected.
  • the energy must be above a threshold value of 0.03 MPa, in the case of the contrast agents described in WO 93/25242 and WO 94/07539 above a threshold value of 0.1 MPa.
  • the energy required for other contrast agents can be easily determined by a person skilled in the art and is generally in the range from 0.01 to 1 MPa, and the threshold increases with increasing stability of the bubbles.
  • the reduction of the contrast agent concentration possible by the method according to the invention further enables the imaging of areas of the body which do not have enough particles, for example those which do not belong to the RES.
  • the tissue flow is represented by the detection of the contrast agent in very fine blood vessels, which due to their small cross-section can only absorb very small amounts of contrast agent (e.g. in the heart muscle, in the liver, in the kidney, in the muscles, in the skin , in the base of the eye, in lymphatic vessels, in lymph nodes, in the urinary tract, in tubes and in small and large body cavities).
  • the advantages of the method according to the invention are particularly clear if location-, structure- or tissue-specific contrast agents can be determined. Such specific contrast agents are described, for example, in WO 94/07539.
  • Sound pressure amplitudes are in the range from 0.01 to 5 MPa, preferably from 0.03 to 0.2 MPa.
  • the HF sound impulses have 1 to 50 pulses, preferably 2 to 8 pulses.
  • the sound transducer is advantageously excited with the aid of a function generator, by means of which RF sound impulses with an adjustable amplitude and an adjustable mean frequency (f ⁇ ) in the range from 0.3 MHz to 22 MHz, preferably from 1 MHz to 11 MHz, and with 0.5 to 20 periods, preferably with 1 to 5 periods. It has been found to be particularly advantageous to evaluate frequencies that are lower than the average frequency f ⁇ of the sound transducer (transmitter).
  • harmonic signal components or signals in the upper sideband receive improved penetration depth and / or spatial resolution, which is particularly advantageous in the representation and in Doppler measurements.
  • the circuit according to the invention for performing the method described above comprises a function generator, the output of which is connected via a T / R switch (transmitter / receiver, transmitter / receiver) which is synchronized by the function generator and, seen in the message flow direction, behind which a signal processing device is connected to the oscillator of an acoustically highly damped, electrically adapted, broadband transducer element.
  • a function generator the output of which is connected via a T / R switch (transmitter / receiver, transmitter / receiver) which is synchronized by the function generator and, seen in the message flow direction, behind which a signal processing device is connected to the oscillator of an acoustically highly damped, electrically adapted, broadband transducer element.
  • the function generator is connected to the input of a converter, the output of which is connected to a signal processing system.
  • the T / R switch when the T / R switch is set to "transmit”, the surge excitation generated by the function generator is applied to the oscillator of the converter, and when the T / R switch is set to "receive” that by the Transducer received signal passed on to the evaluation system.
  • the input and the output of the converter are separated, so that a T / R switch is not necessary.
  • the transducer element is constructed so that the sound intensity emitted by it, as a function of frequency, is in the frequency range below the
  • Excitation or center frequency f ⁇ has a positive first derivative according to the frequency, this derivative being approximately constant, particularly in the working area, or that the sound intensity itself has a constant value in the working area. Because of this approximately linear
  • Frequency response in the work area can have a similar frequency response, especially an attenuation, in the
  • Scope to be balanced. As a result of this circuit and the transmission used, it is possible for the Change the frequency used without changing the transducer. In addition, the optimal ratio of spatial resolution and frequency resolution can be selected when evaluating spectra for material characterization, especially for tissue characterization.
  • the method according to the invention can advantageously be carried out with the aid of a circuit which carries out a multi-element converter with converter elements which receive signals in a phase-delayed manner in order to carry out a phase series or a dynamically focused process.
  • this circuit the output of a function generator using an n-way signal divider, n computer-controlled time delay circuits and n T / R switches, which are controlled by the function generator or by a computer, with the inputs of n acoustically highly damped, electrically adapted, broadband transducer elements connected, the outputs of which are each connected to an m-way signal divider via the n T / R switches.
  • m-way signal dividers are each connected via m time delay circuits and m fixed or variable frequency band selection circuits and also via a circuit for phase correct summation and, if appropriate, for signal division to a system for the selective further processing of m frequency bands.
  • a material is introduced into the examination area to be exposed to the ultrasonic waves, by means of which non-linear vibrations are generated in this area by the interspersed ultrasonic waves;
  • the irradiation of two separate signals produces a stronger received signal, the frequency of which is a combination of the frequencies of the irradiated signals, in particular their sum frequency or difference frequency.
  • the sum frequency is of particular interest in view of the higher spatial resolution that can be achieved.
  • the one transducer element can be excited by means of two RF excitation pulses, but it is also possible to excite two separate transducer elements each with a single RF excitation pulse, the mean frequencies of these RF excitation pulses being different and lower than half the upper limit frequency of the working range.
  • Frequency f + f is used. This phenomenon enables a greater depth of penetration at high observation frequencies.
  • the same materials and means used in the method for evaluating the harmonic frequencies of the excitation frequency can be used as materials or means which produce the nonlinearity. It is possible to use essentially the same circuit elements, but with the addition of a second RF generator.
  • the second signal is always emitted in the direction of the first signal and begins for the purpose of reducing the average power radiated into the examination area approximately 1 to 2 periods earlier and continues until the end of the first excitation pulse signal.
  • the second signal from the second generator is influenced by suitable delay circuits in such a way that after passing through the T / R switch it runs to the same transducer elements in the transducer and is emitted in the same direction as the first transmission signal.
  • the circuit matrix then receives signals at the sum frequency.
  • the T / R switch is controlled by the second transmit signal, which takes longer.
  • FIG. 2 shows a schematic sectional view of a sample vessel
  • Fig. 3 shows a curve of the sound power as
  • the central computer 15 controls both the course of the measurement and its evaluation.
  • the output 2 of the generator 1 leads to a transmitter / receiver switch referred to as a T / R switch 3, which, as shown schematically, is synchronized by the generator 1.
  • the T / R switch 3 can also be controlled directly by the computer 15.
  • the output of the T / R switch 3 is connected to a broadband, adapted and focused converter element 4.
  • the special properties of the converter element 4 are shown schematically in FIG. 3.
  • the transducer can also have spatially and electrically separate transmitter and receiver transducer elements. In this case, the T / R switch 3 is unnecessary. Another converter element for emitting a second, independent high-frequency signal is advantageously present.
  • the signal received by the converter element 4 is sent via the switched T / R switch to a broadband preamplifier 16, behind which an anti-alias filter 17 is connected in the case of digital frequency analysis.
  • the broadband preamplifier 16 has a bandwidth> f o max.
  • the filter 17 has a cut-off frequency of 10 MHz, for example.
  • a fast A / D converter 18 follows the filter, in which the signal is digitized, for example with a Nyquist frequency of 12.5 MHz.
  • the further processing of the signal is carried out in a digital storage oscilloscope and in the central computer.
  • a plotter 19 is connected behind the A / D converter 18.
  • Fig. 1 shows that the A / D converter from the function generator 1 is triggered.
  • the digitized signal is stored and processed in a manner known per se. It is specifically for required
  • Fig. 2 shows schematically the geometry of a vessel with which the measurement results given below were obtained.
  • the transducer 4 is arranged in a sample container 20. It is a 17 MHz transducer that is broadband, matched and focused.
  • the sample vessel 20 contains water.
  • Two films 21 delimit a sample area in which 10 mg of ultrasound contrast medium are dissolved in 3 ml of H 2 O.
  • the signals reflected or backscattered in the measuring area between the films 21 contain certain components which are obtained by mutual action of the transmission pulse (with f 0 ) and the non-linear contrast medium introduced into the measurement object.
  • Fig. 3 shows schematically the frequency band of the transducer element in the transducer. It can be seen that the frequency response of the oscillator in the transducer is quasi-linear in the working area.
  • the frequency response in the work area can be used to compensate for an identical frequency response in the tested sample, but the frequency response in the tested sample can also be subsequently corrected by weighting.
  • a time span of interest in the time range is selected for the measurement with the aid of a computer-controlled gate circuit (not shown). You can also choose different time periods.
  • the assigned spectrum is calculated using an FFT circuit (Fast Fourier Transformation), and examples of such spectra are shown in FIGS. 4 to 9.
  • FFT circuit Fast Fourier Transformation
  • Figures 4 to 8 each show the spectrum over the time window. To the spectral components in these figures To show clearly, a long time window, and thus a poor spatial resolution, was chosen.
  • the signal shown in the upper part of FIG. 4 is a medium power spectrum which was obtained behind the low-pass filter with a Nyquist frequency of 50 MHz.
  • FIG. 5 shows the backscatter signal from the sample chamber without ultrasound contrast medium.
  • FIG. 6 shows the backscatter signal 7 minutes after the addition of 10 mg of contrast medium in 3 ml of H 2 0. A clear peak can be seen at 2 ⁇ f o .
  • FIG. 7 shows a measurement after 21 minutes under the conditions given in FIG. 5.
  • a frequency f 0 3 MHz was used.
  • the recorded spectrum clearly shows the first and second harmonics at 6.0 MHz and 9.0 MHz.
  • Fig. 8 shows the backscatter signal 15 minutes after the addition of an ultrasound contrast agent in a small concentration.
  • the spectrum shown in the upper part of FIG. 8 shows the subharmonic at 1/2 f o , the superharmonic at 3/2 f o and the first harmonic at 2 f Q with a relatively high frequency resolution.
  • the spectrum shows backscattering only at the excitation frequency.
  • the transmission signal from the function generator 1 (frequency f) is given by the output 2 to an n-way signal divider 5.
  • the signal is divided into one branch per converter element.
  • the converter elements 4.1 ... 4.n receive the signal via delay circuits 7.1 ... 7.n and via the T / R switches 3.1 ... 3.n, which are controlled by the generator or the computer.
  • the computer sets the time delay for each transducer element so that the desired directional characteristic is generated on the transducer at the selected transmission frequency.
  • the same directional characteristic is set by the computer in the receiver part through corresponding time delays.
  • the signal received at the transducers 4.1 ... 4.n is sent via the T / R switches 3.1 ... 3.n to broadband preamplifiers 6.1 ...
  • each of which sends a signal to an m-path Signal divider 10 supplies, to the message current below suitably controlled or adjusted delay circuits 11 are connected, feed the circuits 12 for frequency band selection. Behind them are circuits for the phase correct summation of the frequency bands and, if appropriate, for the signal division. This is followed by the selective further processing of the individual frequency bands with the aid of methods known per se.
  • frequencies that are not identical frequencies to f 0 for example 1/2 f 0 and 2 f 0 , is carried out.
  • the delay circuits can be variable or fixed.
  • the distribution of the received signals on the m-way signal divider generates the desired number of frequency bands, the position and width of which are adjusted with the aid of band filters.
  • the division can take place in such a way that the received signal is mixed with an auxiliary signal which is derived from the original signal and deviates depending on the frequency band in such a way that the individual bands can work with uniform components in the subsequent stages.
  • the frequency band around f Q gives the usual results, while the other bands largely frequency-shifted and non-linear signal components from the interaction of the
  • the further processing steps and signal analyzes can be carried out in any desired frequency channel or in different parallel frequency channels in accordance with known procedures.
  • a second generator 1 shown on the right in FIG. 10, which is connected to the T / R switches 3.1 ... 3.n via signal dividers and delay lines.
  • the second generator 1 makes it possible to expose the ultrasonic waves to at least that spatial area of the examined object which is determined by the directional characteristic at that time and the receiver gate.
  • the construction can be such that, in addition to the broadband transducer elements described, the transducer contains at least one further, likewise broadband transmit transducer, which is preferably electrically separated from the others and is fed by the second, independent transmit generator 1.
  • the two transmission signals can also be electrically superimposed on one another in such a way that the same transducer element is used.
  • Fig. 11 shows (in the upper half of the figure) in
  • Time range the backscatter signal which is caused by a contrast medium, as described in WO 93/55242, with weak excitation with a 5 MHz burst with an amplitude of 0.1 MPa.
  • Fig. 12 shows the backscatter signal at an excitation with an A mplitude of 0.34 MPa under otherwise identical test conditions as for Fig. 11.
  • the larger backscattering portion of the contrast agent in the time domain can be clearly recognized.
  • the signals can be clearly determined at 2 f Q and 3 f o .
  • 13 shows the backscatter signal with an excitation with an amplitude of 1 MPa.
  • the backscattering portion of the contrast medium is evidently higher in the time domain (upper half of the figure) than the reflections of the transmission pulses, and it should be noted that 1 scale marking in the ordinate corresponds to 5 mV.
  • the signals can be clearly recognized at 1/2 f 0 , f o , 3/2 f 0 , 2 f 0 , 5/2 f 0 3 f 0, '7 /' 2 fo and 4 fo
  • the signal at 2 f 0 has an intensity approximately equal to the echo de emitted frequency (f 0 ).

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Molecular Biology (AREA)
  • General Health & Medical Sciences (AREA)
  • Pathology (AREA)
  • Radiology & Medical Imaging (AREA)
  • Biophysics (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Medical Informatics (AREA)
  • Veterinary Medicine (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Public Health (AREA)
  • Hematology (AREA)
  • Nonlinear Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

Abstract

L'invention concerne un procédé de reproduction graphique sélective et/ou d'évaluation du spectre Doppler d'objets qui opposent une résistance limitée à des intensités sonores, par exemple des organes et des tissus biologiques, ledit procédé faisant appel aux ultrasons. Selon ce procédé, on introduit un matériau dans la zone d'examen exposée par la suite aux rayonnements acoustiques, puis on génère dans cette zone d'examen des vibrations non linéaires en l'irradiant avec des ondes ultrasoniques et on utilise un transducteur ultrasonique pour évaluer le signal ainsi obtenu. L'invention concerne également un circuit permettant la mise en oeuvre de ce procédé.
EP95936497A 1994-11-01 1995-10-13 Procede aux ultrasons et circuits permettant la mise en oeuvre de ce procede Ceased EP0789536A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US332746 1994-11-01
US08/332,746 US5678553A (en) 1994-11-01 1994-11-01 Ultrasonic processes and circuits for carrying out those processes
PCT/EP1995/004050 WO1996013213A2 (fr) 1994-11-01 1995-10-13 Procede aux ultrasons et circuits permettant la mise en oeuvre de ce procede

Publications (1)

Publication Number Publication Date
EP0789536A2 true EP0789536A2 (fr) 1997-08-20

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EP95936497A Ceased EP0789536A2 (fr) 1994-11-01 1995-10-13 Procede aux ultrasons et circuits permettant la mise en oeuvre de ce procede

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Country Link
US (1) US5678553A (fr)
EP (1) EP0789536A2 (fr)
JP (3) JPH10507672A (fr)
KR (1) KR100380126B1 (fr)
CN (1) CN1154436C (fr)
AU (1) AU698398B2 (fr)
CA (2) CA2204161C (fr)
IL (1) IL115832A (fr)
NO (2) NO325566B1 (fr)
NZ (1) NZ295149A (fr)
TW (1) TW318140B (fr)
WO (1) WO1996013213A2 (fr)
ZA (1) ZA959217B (fr)

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CA2666047A1 (fr) 1996-05-09
MX9702842A (es) 1997-07-31
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AU698398B2 (en) 1998-10-29
WO1996013213A2 (fr) 1996-05-09
TW318140B (fr) 1997-10-21
ZA959217B (en) 1996-05-27
CA2204161A1 (fr) 1996-05-09
KR100380126B1 (ko) 2003-08-02
WO1996013213A3 (fr) 1996-08-01
NO972029L (no) 1997-04-30
CN1162250A (zh) 1997-10-15
NO20072892L (no) 1997-04-30
CA2204161C (fr) 2009-09-29
US5678553A (en) 1997-10-21
CN1154436C (zh) 2004-06-23
JP2007283119A (ja) 2007-11-01
NZ295149A (en) 1998-10-28
KR970706759A (ko) 1997-12-01
NO972029D0 (no) 1997-04-30
AU3842495A (en) 1996-05-23
IL115832A (en) 1998-12-06
JP2009119299A (ja) 2009-06-04

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