Method and device for a blood velocity determination

• US 6,261,233 B1
• Filed: 07/01/1998
• Issued: 07/17/2001
• Est. Priority Date: 01/05/1996
• Status: Expired due to Fees

• Current Assignee: Sunlight Medical Ltd. (Beammed Ltd.)
• Original Assignee: Sunlight Medical Ltd. (Beammed Ltd.)
• Inventors: Kantorovich, Edward
• Primary Examiner(s): Jaworski, Francis J.
• Application Number:
  US09/101,149
• Time in Patent Office: 1,112 Days
• Field of Search: 600/454-456, 738/612.5, 738/612.8, 73/190.3, 73/190.7, 367/100, 367/89-90
• US Class Current: 600/454
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00

Abstract

A method of determining the velocity of a flowing material, suspended in a liquid and flowing in a conduit, including irradiating the conduit with ultrasonic waves, detecting first Doppler-shifted reflections of the waves from the material, which first reflections have a positive Doppler-shift, and detecting second Doppler shifted reflections of the waves from the material, which second reflections have a negative Doppler-shift. The flow velocity is estimated based on the extent of the positive and negative Doppler-shifts. The first and second reflections may be summed to form a composite signal and the range of Doppler-shifts in the composite signal is used to estimate the flow velocity.

Claims

1. A method for determining a flow velocity of a flowing material suspended in a liquid and flowing in a conduit, comprising:

irradiating the conduit with ultrasonic waves, wherein the conduit is a blood vessel;

detecting first Doppler-shifted reflections of the waves from the flowing material, wherein the first Doppler-shifted reflections have a positive Doppler-shift;

detecting second Doppler-shifted reflections of the waves from the flowing material, wherein the second Doppler-shifted reflections have a negative Doppler-shift;

filtering at least one of the first and second reflections to provide a peak signal-amplitude, wherein the peak signal amplitude is substantially velocity independent to provide first and second reflection signals;

generating a composite signal using the first and second reflection signals; and

estimating the flow velocity as a function of the composite signal.

2. The method according to claim 1, wherein the step of generating the composite signal comprises combining the first and second Doppler-shifted reflection signals to form the composite signal, and wherein the step of estimating the flow velocity comprises determining a range of Doppler-shifts in the composite signal.

3. The method according to claim 1, wherein the step of generating a composite signal comprises summing a spectra of the first and second Doppler-shifted reflection signals to form a composite spectrum.

4. The method according to claim 1, wherein the estimation of the flow velocity comprises:

determining a maximum velocity of a flow; and

determining a flow-average velocity of the flow as a function of the determined maximum velocity.

5. The method according to claim 1, wherein the estimation of the flow velocity comprises:

determining a quadric-average velocity of a flow; and

determining a flow-average velocity of the flow as a function of the determined quadric-average velocity.

6. The method according to claim 1, wherein the estimation of the flow velocity comprises:

determining a relative attenuation between the first Doppler-shifted reflections and the second Doppler-shifted reflections;

determining a first travel time of the first Doppler-shifted reflections from the flowing material to a first detector;

determining a second travel time of the second Doppler-shifted reflections from the material to a second detector; and

determining an attenuation-per-unit length of the first and second Doppler-shifted reflections as a function of the determined first and second travel times and of the determined relative attenuation.

7. The method according to claim 6, further comprising:

determining a first angle between the first Doppler-shifted reflections and a flow direction of the material as a function of the determined first and second travel times.

8. The method according to claim 7, wherein a flow has a substantially circular cross-section, and further comprising:

determining a diameter of one of the flowing material and the conduit; and

correcting the diameter as a function of the first angle.

9. The method according to claim 6, further comprising:

converting the first and second travel times to distances as a function of a measured velocity of ultrasound waves in a soft tissue surrounding the flowing material.

10. The method according to claim 1, wherein a flow of the flowing material has a pulse, and further comprising:

determining a first particular phase of the pulse of the flow of the first Doppler-shifted reflections;

determining a time delay to provide a second particular phase for the second Doppler-shifted reflections; and

delaying a signal generated by one of the first and second Doppler-shifted reflections as a function of the time delay.

11. The method according to claim 10, wherein the step of determining the first particular phase comprises determining the first particular phase from changes in a diameter of the conduit.

12. The method according to claim 11, wherein the changes in the diameter are determined using ultrasonic sensors.

13. The method according to claim 11, wherein the step of determining the first particular phase comprises determining the first particular phase as a function of reflections from the conduit.

14. The method according to claim 10, wherein the step of determining the first particular phase comprises determining the first particular phase as a function of the first Doppler-shifted reflections from the flowing material.

15. A method for determining a pressure exerted by a flowing material on a conduit, comprising:

irradiating the conduit with ultrasonic waves, wherein the conduit is a blood vessel;

detecting first Doppler-shifted reflections of the waves from the flowing material, wherein the first Doppler-shifted reflections have a positive Doppler-shift;

detecting second Doppler-shifted reflections of the waves from the flowing material, wherein the second Doppler-shifted reflections have a negative Doppler-shift;

filtering at least one of the first and second reflections to have a peak signal-amplitude, wherein the peak signal amplitude is substantially velocity independent;

generating a composite signal using the first and second reflections;

estimating a flow velocity of the flowing material as a function of the composite signal;

determining a cross-section of the conduit;

determining an equivalent length of the conduit; and

determining the pressure as a function of the determined cross-section of the conduit, the determined equivalent length and the estimated flow velocity.

16. The method according to claim 15, wherein a flow of the flowing material has a pulse wave, and wherein the determination of the equivalent length comprises:

determining a velocity of the pulse wave;

determining a travel time of the pulse wave along the conduit; and

determining the equivalent length as a function of the determined pulse wave velocity and the determined travel time.

17. The method according to claim 15, wherein the blood pressure determination comprises non-invasively determining a time-dependent blood pressure at a first location on a body and repeating the non-invasively determination of the time-dependent blood pressure at a plurality of locations.

18. The method according to claim 17, wherein the non-invasively determination of the time-dependent blood pressure comprises non-invasively determining a local blood pressure only as a function of local measurements.

19. The method according to claim 15, further comprising:

non-invasively determining a first local blood pressure at a first location;

non-invasively determining a second local blood pressure at a second location; and

comparing the first and second local blood pressures to determine the presence of a stenosis.

20. A method for non-invasively determining a local blood pressure at a location of a blood vessel in a circulatory system, the circulatory system coupled at one end by a heart and at a capillary end by capillaries, the blood vessel allowing a flowing material to flow therethrough, the method comprising:

determining a local impedance to a flow of blood in the blood vessel;

determining an end impedance to the flow of the blood at the capillary end of the circulatory system;

irradiating the blood vessel with ultrasonic waves;

detecting first Doppler-shifted reflections of the waves from the flowing material, wherein the first Doppler-shifted reflections have a positive Doppler-shift;

detecting second Doppler-shifted reflections of the waves from the flowing material, wherein the second Doppler-shifted reflections have a negative Doppler-shift;

filtering at least one of the first and second reflections to have a peak signal-amplitude, wherein the peak signal amplitude is substantially velocity independent;

generating a composite signal using the first and second reflections;

estimating a flow velocity of the flowing material as a function of the composite signal;

determining a blood flow volume as a function of the estimated flow velocity; and

determining an instantaneous local blood pressure at the location of the blood vessel as a function of the determined local impedance, the determined end impedance and the determined blood flow volume.

21. The method according to claim 20, further comprising:

determining a reflectance at the capillary end; and

determining the local and end impedances as a function of the determined reflectance.

22. The method according to claim 21, further comprising:

determining a complex value of the reflectance by measuring an amplitude and a phase of reflected pulse waves.

23. The method according to claim 21, wherein the step of determining the reflectance comprises:

determining the reflectance before the capillaries are dilated; and

determining a further reflectance after the capillaries are dilated.