Classifications

• • 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
  • A61B8/483—Diagnostic techniques involving the acquisition of a 3D volume of data
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/06—Measuring blood flow
  • A61B8/065—Measuring blood flow to determine blood output from the heart
• • 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
  • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
  • G01S15/88—Sonar systems specially adapted for specific applications
  • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
  • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
  • G01S15/8979—Combined Doppler and pulse-echo imaging systems
• • 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
  • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
  • G01S15/88—Sonar systems specially adapted for specific applications
  • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
  • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
  • G01S15/8993—Three dimensional imaging systems

Definitions

• the present invention creates a new method which makes it possible to instantly know essential characteristics such as cardiac output, speed of flow of blood, in particular in the aorta, acceleration at the start of systole and , therefore, it becomes possible to intervene very quickly, which is decisive for some patients, especially for mechanically ventilated patients with serious conditions.
• the method for determining cardiovascular characteristics externally is characterized laughed at by determining the cross section of a blood vessel, by determining the distance between a substantially cross section of the blood vessel and part of the patient's body surface, by emitting inside regular time intervals of the ultrasonic bursts, in that the Doppler echo of said bursts is collected at a time interval corresponding to the distance separating the vessel from the part of the patient's body surface, in that '' the successively collected echoes are converted into directional Doppler signals, in that said directional Doppler signals are converted into digital signals, in that one alternately stores a number of digital signals which is a power of 2 in two buffers for short successive sampling time intervals, in that the digital signals coming successively from l are processed alternately by Fourier transformation and in real time 'and the other memory buffers to establish a frequency spectrum and. amplitudes corresponding to each sampling time, and in that the average frequency is calculated
• Fmoy ⁇ (A 2 .F) ⁇ A 2 to obtain a curve as a function of time, each period of which is the image of a systole.
• the invention also extends to a device for implementing the above method, device which by its realization can be produced in a small volume and at a low price given the specificity of its components intended to fill only a limited number of functions although in very short times, and thus the miniaturization that it is possible to carry out of the device makes it possible to implement it even outside intensive care units.
• the information provided by the device can be obtained for the most part in direct reading, for example on a cathode-ray screen while allowing as much, possibly, graphic recordings at characteristic moments of a treatment or during the sudden evolution of the patient's condition.
• the device comprises a transducer for the emission of bursts of ultrasound at regular time intervals and for reception of the resulting Doppler echo, a directional circuit for obtaining signals Directional Doppler, an analog to digital converter connected to the directional Doppler circuit, two buffer memories connected to the analog to digital converter and receiving alternately a number of significant image points of the directional Doppler signal, a computer connected to the two buffers and successively processing the illustrative data points stored in said buffer memories for the formation of a spectrum of amplitudes and frequencies respectively illustrating half of the significant points stored each time in each of the buffer memories, a first memory for storing the amplitudes and frequencies spectrum characteristics and a computer connected to said memory to perform at least the calculation ⁇ (A 2 . F)
• the invention finds a particularly important application in the establishment of cardiovascular characteristics, in particular at the level of the ascending aorta.
• the transducer is placed in the suprasternal fossa behind the manubrium, being directed downwards to intercept a section of the ascending aorta close to the sigmoid valves.
• Fig. 1 is a block diagram of the device for implementing the method for determining cardiovascular characteristics, object of the invention.
• Fig. 2 is an explanatory anatomical diagram.
• Fig. 3 illustrates two curves for obtaining a Doppler signal.
• Fig. 4 is a diagram illustrating a processing phase of the method of the invention.
• Fig. 5 schematically illustrates a spectrum obtained by Fourier transformation from the Doppler signals illustrated schematically in FIG. 3.
• Fig. 6 is an illustrative curve of cardiovascular characteristics obtained according to the invention in real time.
• Fig. 7 is a curve illustrating a three-dimensional representation obtained according to the invention.
• Fig. 8 illustrates the so-called three-dimensional representation obtained from the cardiovascular characteristics determined according to the invention from the curves of FIG. 6.
• Figs. 9 and 9a are vector representations illustrating the speed of the blood cells in a vessel during a sampling time defined in relation to FIG. 3.
• 1 designates a transducer for the emission of signal bursts and the reception of Doppler signals through a gate 2 leading to a processing circuit 3 for forming directional Doppler signals, that is to say all positive and for example between 0 and 7 KHz.
• the transducer 1, door 2 and circuit 3 assembly is adjusted as illustrated in FIG. 3 to first obtain Doppler samples, that is to say that in successive time intervals T, T 1 ... T n , for example of 10 -4 s, first of all a burst of high frequency pulses for example at 4 MHz for a time t.
• the frequency of the bursts of pulses is chosen taking into account the approximate known speed of the blood cells, generally between 0 and 150 cm / s in the ascending aorta during a systole so that the Doppler signal, that is to say the difference between the transmitted frequency and the received frequency, ie a directional frequency preferably included in the audible frequencies, for example between 0 and 7 KHz, as indicated above.
• FIG. 2 To determine the cardiovascular characteristics at the level of the ascending aorta, the procedure is as illustrated in FIG. 2.
• 4 designates the left ventricle of the heart
• 5 designates the sigmoid valves
• 6 the ascending aorta.
• the transducer 1 is applied at the level of the suprasternal fossa 7, that is to say behind manubrium 8 of the patient and said head 1a is maintained so that its axis is substantially vertical and directed downward as illustrated by axis 9, so that said axis is approximately concentric to a cross section 10 of the part of the aorta ascending near the sigmoid valves.
• An anatomical study can moreover be carried out for each patient concerned before the examination by means of an ultrasound observation making it possible to locate the section 10 at approximately 6 cm from the suprasternal pit 7 and, likewise, the aortic section at the Cut level 10 is normally known from tables or easily determined by ultrasound observation.
• the time t 1 must be set to elapse between the end of the burst of high frequency pulses emitted during the time t and the opening of the door 2 making it possible to receive the Doppler echo.
• the time t 1 is for example between 60 and 80 ⁇ s, the door 2 then remaining open for a time t 2 for example between 1 and 3 ⁇ s.
• said time t 2 represents the sampling time of the Doppler frequency.
• the section 10 has a diameter of approximately 3 cm and a thickness of between 0.75 and 2.25 mm when the level at which the echo is to be appreciated is 4.5 to 6 cm away from the receiving transmitting part of the transducer head 1a.
• the directional Doppler signal from circuit 3 is applied to an analog-to-digital converter 11 intended for alternately loading two buffer memories 12 and 13 which are connected to a processing computer 14 in which said buffer memories are alternately discharged as illustrated diagrammatically in fig. 4.
• each buffer memory 12, 13 receives successively a integer number of points, which is a power of 2 and, preferably, each memory receives 128 points constituting the digital image of the Doppler signal corresponding to a sampling time period of 5 ms.
• the processing calculator 14 comprises a calculation software 14a causing it to perform a Fourier transformation for each of the data received alternately from one and the other memories in successive sampling time periods of 5 ms.
• Fig. 5 shows that the processing computer 14 establishes, during each 5 ms period of time, a spectrum of 64 values of frequency F and 64 values of amplitude A.
• the values of the frequencies and the amplitudes thus calculated during each lapse of time of 5 ms are stored in memories 15 of amplitudes and frequencies connected to a computer 16 (fig. 1) which, in the example described in the following , is designed to perform two types of calculations and which can therefore be constituted in the form of a unit specific to these only types of calculations, which allows it to be performed in reduced form and relatively inexpensively.
• the computer 16 receiving the data from the memories 15 performs from each spectrum conforming to that of FIG. 5 an average frequency calculation in real time, that is to say as each spectrum is established.
• each pulse I of the curve of FIG. 6 corresponds to the acceleration that the blood undergoes at the start of the systole, the front edge of said curve thus being a very important illustration of the cardiac state since the acceleration that the blood undergoes in the ascending aorta near the valves sigmoid is an image of the contractility of the heart muscle.
• each pulse I also corresponds to the volume of blood ejected during systole, this volume can thus be easily calculated by the computer 16 which only has to carry out the integral of each pulse.
• the section of the aorta is also known as explained in the foregoing, the product of the velocity by this section can also be easily executed by the computer to know the blood flow to each systole.
• the curve of fig. 6 being a frequency curve as a function of time and this curve delimiting with precision the successive sytoles and diastoles, the durations of the latter are also determined in a simple manner.
• the computer 16 is normally connected to a screen 17 making it possible to permanently display the characteristics calculated by the computer.
• a keyboard 18 is associated with the computer 16 to allow the operator to store in memory for a more or less long time, for example 5 to 7 seconds, the coordinates of the curve of FIG. 6 and thus allow then to make a plot by means of a writer 19 of the data of the curve of FIG. 6 which have been frozen in memory for the time selected above. It can be seen from the above that, by the means described, the invention makes it possible, for example at each cardiac period, to know the blood volume ejected during systole, to know the ejection time, the maximum blood speed, maximum blood acceleration and cardiac output, results which allow them to appreciate the cardiovascular state and in particular the contractility characteristics of the muscle.
• the method of the invention also extends to the determination and the visualization of the differences in speed of the blood glovules in the vessel studied by showing the results obtained in the form of a three-dimensional plot which thus appears in the manner a relief representation.
• the amplitude and frequency spectra of the memory 15 are transferred to the computer 16 to be stored and processed there in deferred time, that is to say that the succession of amplitude and frequency data allows from the curve according to fig. 5 to trace at the end of each sampling time of 5 ms a first envelope of the spectrum as illustrated by the curve E 1 of FIG. 7.
• the computer 16 is programmed to calculate and then trace the envelope E 2 of the spectrum of the second sampling time of 5 ms.
• the plotting of the curve E 2 and of the following ones is carried out according to coordinates shifted in the time of regular measurements, images of the sampling time of 5 ms as indicated in fig. 7.
• the calculation of the plot of the curves E 1 , E 2 ... E n of the envelopes of the successive spectra is carried out as shown in FIG. 7 so that only the parts of the envelopes not hidden by the preceding envelopes appear.
• the three-dimensional trace described is obtained by acting on the keyboard 18 of the computer 16 to freeze in the main memory of the latter the data of the successive spectra at 64 amplitudes and 64 frequencies. memories 15 for a time, for example of about 10 seconds or more, to then allow and in delayed time the three-dimensional tracing over a significant period of time corresponding for example to a respiratory cycle, which then allows the observer to '' appreciate the cardiac cycles taking into account the interferences produced on the aortic circulation in the course of the respiratory cycles.

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• 1984
  • 1984-12-07 FR FR8418779A patent/FR2574280B1/fr not_active Expired
• 1985
  • 1985-12-06 WO PCT/FR1985/000353 patent/WO1986003593A1/fr not_active Application Discontinuation
  • 1985-12-06 EP EP19850906077 patent/EP0205487A1/fr active Pending
  • 1985-12-06 JP JP50533885A patent/JPS62501269A/ja active Pending

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