WO2001050962A1 - Dispositif de mesure du mouvement de valvules cardiaques - Google Patents

Dispositif de mesure du mouvement de valvules cardiaques Download PDF

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Publication number
WO2001050962A1
WO2001050962A1 PCT/AU2001/000019 AU0100019W WO0150962A1 WO 2001050962 A1 WO2001050962 A1 WO 2001050962A1 AU 0100019 W AU0100019 W AU 0100019W WO 0150962 A1 WO0150962 A1 WO 0150962A1
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WIPO (PCT)
Prior art keywords
signals
frequency
filter
bandwidth
amplified
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Application number
PCT/AU2001/000019
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English (en)
Inventor
Tsuyoshi Koga
Akio Miyazaki
Original Assignee
Western Sydney Area Health Service
Kyushu University
Toitu Co., Ltd.
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 Western Sydney Area Health Service, Kyushu University, Toitu Co., Ltd. filed Critical Western Sydney Area Health Service
Priority to AU2001226534A priority Critical patent/AU2001226534A1/en
Publication of WO2001050962A1 publication Critical patent/WO2001050962A1/fr

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Classifications

    • 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
    • G01S15/02—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems using reflection of acoustic waves
    • G01S15/50—Systems of measurement, based on relative movement of the target
    • 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
    • A61B8/488—Diagnostic techniques involving Doppler signals

Definitions

  • the present invention relates generally to a process for the qualification, quantification, or both, of at least one relationship between objects which move with respect to one another. More specifically, the present invention relates to such qualification, quantification or both, between such objects in a closed system.
  • the process of the present invention is particularly valuable for non-invasive determination of the temporal relationship between the opening and closure of the heart valves in a living subject. Additionally disclosed is an electronic module for carrying out the process.
  • Murata and co-workers studied systolic time intervals of foetal heart movements using simultaneous recording of foetal electrocardiograms (ECG) and Doppler cardiograms (DCG). They used an analogue cardiac Doppler signal conditioned by a 600-2000 Hz analogue band-pass filter to detect all signals of cardiac valve opening and closing (see Murata Y et al. (1974) "Systolic Time Intervals of the Fetal Cardiac Cycle”. 44 Obstetrics and Gynecology 224; see also Murata Y et al. (1978) "Antepartum evaluation of the pre-ejection period of the fetal cardiac cycle”.
  • the present invention provides an improved process of obtaining accurate, non-invasive, quantification of the temporal relationship between heart valve movements.
  • the present invention consists in a process for either quantifying or qualifying or both, at least one relationship between at least two objects which move with respect to one another, the process comprising the steps of:
  • the at least one relationship which the process of the present invention can be used to determine is a physical relationship, a temporal relationship, or any other relationship which is desirably determined on the basis that the at least two objects move in relation to one another.
  • the present process assists in scientifically defining the moving relationship between the at least two objects.
  • the process is applicable to defining such a relationship where the two objects exist in a closed system and, as a result, are not visible to the naked eye. Moreover, the present process is particularly valuable in providing accurate, non-invasive, determination of, for example, the temporal relationship between the opening and closure of heart valves in a living subject.
  • the present invention consists in a process for quantifying a temporal relationship between opening and closure of at least two heart valves in a living subject, the process comprising the steps of:
  • the process of the present invention is used to determine the temporal relationship between the opening and closure of the heart valves in a foetus.
  • the process can be used in making such a determination in living subjects of all ages.
  • the process of the invention may also be used to provide an accurate definition of the moving relationship between individual leaflets of each heart valve.
  • the lower limit of the frequency range of the raw analogue Doppler frequency shift signals to be amplified is preferably at least about 50Hz.
  • the upper limit of that frequency range is preferably about 10000Hz.
  • the frequency range within which the raw signals are amplified is between about 100Hz and about 8000Hz, more preferably between about 150Hz and about 5000Hz, more preferably still between about 200Hz and about 2000Hz, and most preferably between about 250Hz and about 1500Hz.
  • the sampling rate with which the amplified signals are digitised is preferably at least about 1000Hz. In a preferred embodiment, however, the sampling rate may be anywhere up to about 20000Hz. More preferably, however, the sampling rate may be anywhere between about 2000Hz and about 15000Hz, and more preferably still between about 3000Hz and about 8000Hz. In a most preferred embodiment, the sampling rate with which the amplified signals are digitised is about 4000Hz.
  • sampling rate can be increased is dependent the level of technology available at any one time. Accordingly, the preferred embodiments of the invention provided above should not be read as limiting the sampling rate ranges that may be used in the processes defined above. Indeed, the greater the sampling rate, the more accurate the findings from ultrasound interrogation of the moving objects.
  • the digitised signals are then passed through a plurality, or 'multibank', of frequency filters. While each such filter can have a unique frequency bandwidth which does not overlap the frequency bandwidth of any of the other filters, in other embodiments, the bandwidth of some or all of such filters may overlap one another. In another configuration, an upper limit of the bandwidth range for the first frequency filter can mark a lower limit of the bandwidth range for the second frequency filter, and so on.
  • the multibank includes at least three such filters which are used in carrying out the process according to the invention.
  • bandwidth ranges are as follows:
  • a preferable range for the first frequency filter has a lower limit of about 0Hz.
  • the preferred upper limit for the bandwidth of this frequency filter is about 1000Hz.
  • the range within which the bandwidth for the first frequency filter falls is from about 100Hz to about 800Hz, more preferably still from about 200Hz to about 600Hz, and most preferably from about 250Hz to about 500Hz.
  • the bandwidth range for the second frequency filter preferably falls between about 300Hz and about 1500Hz, more preferably between about 400Hz and about 1300Hz.
  • the bandwidth of the third frequency filter has a lower limit of about 600Hz and an upper limit of about 2000Hz. More preferably, the range of the bandwidth of the third frequency filter is from about 800Hz to about 1800Hz. more preferably still from about 900Hz to about 1600Hz. and most preferably from about lOOOHz to about 1500Hz.
  • each frequency filter is preferably set to record its own frequency bandwidth. Data obtained from such recordation is preferably displayed in any practical format, including numerically and/or graphically. Furthermore, because it is to an appropriate comparison of the frequency filters which an analyst will refer in determining a characteristic of the moving relationship between, for example, two heart valves, it is additionally preferable that all the frequency filters are displayed simultaneously.
  • steps (e). (f) and (g) of the processes according to the present invention certain characteristics of movement of each of the objects are identified by different frequency filters. For example, where the process is being used to determine the temporal relationship between the opening and closure of two heart valves, movement of a first heart valve is identified by a first frequency filter (step (e)). then the exact time of opening or closure of that first valve is identified by a second frequency filter (step (f)). In performing these steps, some comparison may need to be made between the recordings from the two or more frequency filters used in the multibank. Next, both steps (e) and (f) are repeated once again for the second heart valve (step (g)). In performing these steps for the second heart valve, it is preferable that at least one of the frequency filters used is different to one or both of the frequency filters used for analysing movement of the first heart valve. In step (h), a comparison is performed of the results from steps (e) and
  • the present invention also envisages an alternative embodiment in which the data recorded by each individual filter is not displayed, but is processed in combination with the data from one or more of the other filters by a central processing unit.
  • a central processing unit it is not necessary for an analyst to interpret numerical and/or graphical data from each individual filter and compare it in some way to that of one of the others. Rather, an analyst can simply obtain the results of such interpretation as performed by the central processing unit.
  • the central processing unit itself may apply any one or a combination of appropriate algorithms to the data obtained from each filter, depending on the particular relationship which is to be qualified and/or quantified, for example, the temporal relationship between the opening of one heart valve and the closure of another.
  • a number of variables can be determined. For example, where the process is used to quantify the temporal relationship between the relative movement of two or more heart valves, the variables determined relate to the movement of the valves individually and as compared to one another: both the opening and the closure of the mitral and tricuspid valves, as well as the aortic and pulmonary valves are identified.
  • the time periods from mitral valve closure to aortic valve opening, tricuspid valve closure to pulmonary valve opening, aortic valve opening to aortic valve closure, pulmonary valve opening to pulmonary valve closure, aortic valve closure to mitral valve opening and pulmonary valve closure to tricuspid valve opening are examples of the many temporal relationships which are quantified by the process of this invention.
  • the present invention consists in an electronic module for use with an ultrasound device, the module being adapted for incorporation into the electronic circuitry of the ultrasound device to enhance the ability of said device to quantify and/or qualify at least one relationship between at least two objects which move with respect to one another, the module comprising:
  • filtering means to filter the digitised signals, said filtering means comprising at least a plurality of frequency filters, each filter being set to record a signal for its respective frequency bandwidth:
  • the present invention consists in an electronic module for use with an ultrasound device, the module being adapted for incorporation into the electronic circuitry of the ultrasound device to enhance the ability of said device to quantify and/or qualify at least one relationship between at least two objects which move with respect to one another, the module comprising:
  • filtering means to filter the digitised signals, said filtering means comprising at least a plurality of frequency filters, each filter being set to record a signal for its respective frequency bandwidth;
  • processing means to process the recorded signals, said processing means comprising:
  • identifying means to identify a plurality of characteristics of movement for each object in one, a plurality, or all of the recorded signals
  • comparing means to compare the identified characteristics of movement in at least two of the recorded signals for each and both of the at least two objects:
  • Fig. 1 represents a flow chart of the process steps and a schematic representation of the electronic module componentry of the present invention
  • Fig. 2 is a representation of a foetal ECG and DCG illustrating the foetal cardiac pre-ejection period (PEP) as the time from the onset of Q wave to aortic valve opening, and the isovolumetric contraction time (ICT) as the interval between mitral valve closing to aortic valve opening
  • PEP foetal cardiac pre-ejection period
  • ICT isovolumetric contraction time
  • Fig. 4 is a graph illustrating the detection of mitral valve closing signal
  • Fig. 5 is a multiple display for measuring ICT over a series of frequency ranges. Best Mode of Carrying Out the Invention
  • figure 1 which serves the double purpose of illustrating a flow chart representative of the steps involved in carrying out the process, as well as a schematic diagram of a module according to the invention.
  • An ultrasound beam is used to interrogate the mitral, tricuspid, aortic and pulmonary valves (not shown). Once raw analogue data Doppler frequency shift signals have been obtained from the interrogation, the raw signals are amplified in the range from about 250 to about 1500Hz (box 11).
  • the amplified signals are then digitised with a sampling rate of about 4000Hz (box 12).
  • the digitised signals are then simultaneously displayed unfiltered and then passed through a multibank of frequency filters 13 having at least three of such frequency filters 13a, 13b, 13c available for the filtering step of the process.
  • the frequency filters 13a. 13b, 13c themselves are set to display simultaneously their own signal for their respective frequency bandwidth.
  • the filtering is carried out in the frequency range of about 0-1500Hz, where the bandwidth of each of the three frequency filters is about 250- 500Hz for the first frequency filter 13a, 500-lOOOHz for the second frequency filter 13b and 1000-1500Hz for the third frequency filter 13c.
  • appropriate comparison of the displayed signals for each of these filters is carried out (boxes 14 and 15).
  • Movement of each heart valve is identified in one filtered frequency, while the precise time of its commencement of opening or closure is identified on a different filtered frequency (box 14).
  • the temporal relationship between the opening and closure of the four heart valves is quantified, and may be displayed (box 15).
  • Fig. 1 serves the additional purpose of representing a schematic diagram of an electronic module 10 according to the invention.
  • Box 11 represents an amplifier which amplifies the raw signals coming from the ultrasound device which is not depicted, but would be to the left of the diagram.
  • Box 12 is a digitiser which digitises the amplified signals. Once digitised, the signals are then passed through Box 13 which represents a multibank of filters 13a,13b,13c.
  • Box 14 merely represents means for transmitting the filtered signals from Box 13 to the display means Box 15.
  • Box 14 represents such a processing unit which also includes at least a comparator and a memory unit for recording the appropriate algorithms to compare the filtered signals.
  • Box 15 displays the actual data processed by the processing unit (in Box 14).
  • Example 1 provides a more detailed explanation and analysis of the results from a study of foetal heart valve movements in accordance with a preferred embodiment of the invention.
  • Example 1 As shown in Figure 2, with simultaneous recording of the foetal electrocardiogram (ECG) and the Doppler cardiogram (DCG), the pre-ejection period (PEP) can be measured as the time from the onset of the Q wave of the ECG to the aortic opening signal (Ao) of the DCG and the ICT has been identified as the time between the mitral valve closure signal (Mc) and Ao of DCG.
  • ECG foetal electrocardiogram
  • DCG Doppler cardiogram
  • Cardiac Doppler signals were recorded on 40 foetuses between 18 and 40 weeks' gestation.
  • the heart position was first confirmed by B-mode ultrasound imaging.
  • the continuous ultrasound transducer was held manually against each mother's abdomen directing the transmitting beam along the axis of the foetal heart.
  • the transducer had two lead half discs of 3cm radius, one for transmitting the ultrasound beam, the other for receiving its reflection.
  • the transmitted beam was a 2.5MHz plane wave (ultrasound power 10mW/cm 2 ) and the amplifier range was from 250 to 1500Hz.
  • the transducer was fixed.
  • Mc and Ao signals were located from the raw signals monitored on an oscilloscope. Doppler signals were then stored on digital audio tape using a PCM data recorder [RD-101T. TEAC]. A 1- to 3-minute recording time was necessary.
  • Foetal cardiac Doppler signals were recorded with the same equipment and method as mentioned above (see also Fig. 1).
  • Raw signals were digitised with 4000Hz sampling rate and divided into 3 different frequency shift ranges 250-500.
  • 500-1000 and 1000-1500Hz with filter-bank application in the personal computer system.
  • a multiple display of raw signal and 3 filtered signals is shown in Figure 5.
  • Both Mc and Ao signals are detected as sharp spikes on 500-lOOOHz range.
  • Mc and outflow signal following Ao on 250-500 and 1000- 1500Hz ranges respectively. This multiple display system enables us to confirm each cardiac cycle and to identify the Mc and Ao signals without using a foetal ECG.
  • the time scale of this display system can be modulated from lms/cm to 80ms/cm.
  • ICT the interval between the end of Mc signal and beginning of Ao signal measured with a built-in scale device on the screen of 20ms/cm time scale setting.
  • Results Determination of the most suitable digital-filter setting for measuring ICT As shown in Figure 4, Mc signal could be detected in 28 (about 70.0%) and 39 (97.5%) cases of 40 on 375 to 500Hz and 500 to 750Hz frequency shift ranges, respectively.
  • Ao signal could be obtained in 38 (95.0%), 29 (72.5%) and 29 (72.5%) cases on 500 to 750, 750 to 1000 and 1000 to 1500Hz frequency shift ranges, respectively. Consequently it was proved that dividing the raw signals into 3 ranges, 250 to 500, 500 to 1000 and 1000 to
  • 1500Hz frequency shift could be the most suitable digital-filter setting for measuring ICT.
  • this setting we could measure the ICT as the interval between Mc and Ao signals on 500 to lOOOHz range, confirming each cardiac cycle from atrio-ventricular flow and outflow noises on 250-500 and 1000- 1500Hz frequency shift ranges respectively.

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Abstract

L'invention concerne un procédé de quantification d'une relation temporelle entre l'ouverture et la fermeture d'au moins deux valvules cardiaques dans un sujet vivant tel qu'un foetus. Ce procédé consiste a) à examiner ces deux valvules cardiaques avec un faisceau d'ultrasons, et à obtenir des signaux de décalage de fréquence de Doppler analogues bruts à partir de l'examen précédent, b) à amplifier les signaux bruts (11), c) à numériser les signaux amplifiés (12), d) à passer les signaux numérisés au travers d'une pluralité de filtres de fréquence (13), chaque filtre étant configuré pour enregistrer un signal en fonction de sa largeur de bande de fréquence respective, e) à identifier le mouvement d'une première valvule cardiaque dans au moins un premier des signaux enregistrés, f) à identifier l'ouverture et/ou la fermeture de la première valvule cardiaque dans au moins un autre des signaux enregistrés, g) à répéter les étapes e) et f) pour au moins une deuxième valvule cardiaque, et h) à comparer les résultats des étapes e) et f) pour la première et la deuxième valvules cardiaques, et/ou à comparer les résultats des étapes e) et f) avec les résultats de l'étape g), afin de quantifier la relation temporelle entre l'ouverture et/ou la fermeture des deux valvules cardiaques. L'invention concerne également un dispositif destiné à la mise en oeuvre dudit procédé.
PCT/AU2001/000019 2000-01-14 2001-01-12 Dispositif de mesure du mouvement de valvules cardiaques WO2001050962A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001226534A AU2001226534A1 (en) 2000-01-14 2001-01-12 A cardiac valve movement measuring device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPQ5083 2000-01-14
AUPQ5083A AUPQ508300A0 (en) 2000-01-14 2000-01-14 A cardiac valve movement measuring device

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006035380A1 (fr) * 2004-09-28 2006-04-06 Koninklijke Philips Electronics N.V. Methode et appareil de presentation d'informations concernant le comportement d'ecoulement d'un liquide organique mesure externement par ultrasons
US10835201B2 (en) 2017-10-31 2020-11-17 Edwards Lifesciences Corporation Non-invasive wearable heart valve monitor

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986003593A1 (fr) * 1984-12-07 1986-06-19 Institut National De La Sante Et De La Recherche M Procede et dispositif de determination de caracteristiques cardio-vasculaires par voie externe et leur application aux cardiopathies
US4890624A (en) * 1988-03-22 1990-01-02 Air-Shields, Inc. Fetal heart rate counting system using digital signal processing
US5170791A (en) * 1991-03-28 1992-12-15 Hewlett-Packard Company Method and apparatus for calculating the fetal heart rate
US5289820A (en) * 1988-10-17 1994-03-01 The Board Of Regents Of The University Of Washington Ultrasonic plethysmograph
EP0895094A1 (fr) * 1997-07-31 1999-02-03 Esaote S.p.A. Methode d'imagerie bidimensionelle à ultrasons avec dispositif pour l'examen de la puissance doppler

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986003593A1 (fr) * 1984-12-07 1986-06-19 Institut National De La Sante Et De La Recherche M Procede et dispositif de determination de caracteristiques cardio-vasculaires par voie externe et leur application aux cardiopathies
US4890624A (en) * 1988-03-22 1990-01-02 Air-Shields, Inc. Fetal heart rate counting system using digital signal processing
US5289820A (en) * 1988-10-17 1994-03-01 The Board Of Regents Of The University Of Washington Ultrasonic plethysmograph
US5170791A (en) * 1991-03-28 1992-12-15 Hewlett-Packard Company Method and apparatus for calculating the fetal heart rate
EP0895094A1 (fr) * 1997-07-31 1999-02-03 Esaote S.p.A. Methode d'imagerie bidimensionelle à ultrasons avec dispositif pour l'examen de la puissance doppler

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PADMANABHAN ET AL.: "Doppler ultrasound observation of pathological heart valves", IEEE ENGINEERING IN MEDICINE AND BIOLOGY, July 2000 (2000-07-01) - August 2000 (2000-08-01) *
ROUTH: "Doppler ultrasound", IEEE ENGINEERING IN MEDICINE AND BIOLOGY, November 1996 (1996-11-01) - December 1996 (1996-12-01), pages 31 - 40 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006035380A1 (fr) * 2004-09-28 2006-04-06 Koninklijke Philips Electronics N.V. Methode et appareil de presentation d'informations concernant le comportement d'ecoulement d'un liquide organique mesure externement par ultrasons
US10835201B2 (en) 2017-10-31 2020-11-17 Edwards Lifesciences Corporation Non-invasive wearable heart valve monitor
US11723621B2 (en) 2017-10-31 2023-08-15 Edwards Lifesciences Corporation Heart valve monitoring

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