SYSTEM, METHOD AND APPARATUS FOR MEASURING BLOOD FLOW AND BLOOD VOLUME

• US 20130144177A1
• Filed: 02/04/2013
• Published: 06/06/2013
• Est. Priority Date: 02/15/2005
• Status: Active Grant

• Current Assignee: Baxter Healthcare SA (Baxter International Inc.), Baxter International Inc.
• Original Assignee: Cheetah Medical, Inc. (Baxter International Inc.)
• Inventors: Simon, Avram B., KEREN, Hanan
• Granted Patent: US 10,617,322 B2
• Time in Patent Office: Days
• US Class Current: 600/506
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

A method of calculating blood flow in an organ of a subject using output radiofrequency signals transmitted to the organ and input radiofrequency signals received from the organ, the method comprises determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals and using the phase shift to calculate the blood flow in the organ.

Claims

1. An apparatus for determining blood flow in an organ of a subject from output radiofrequency signals transmitted to the organ and input radiofrequency signals received from the organ, the apparatus comprising:

electronic circuitry having an envelope elimination unit designed and configured to reduce or eliminate amplitude modulation of said input radiofrequency signals thereby to provide input radiofrequency signals of substantially constant envelope; and

a signal processing unit for determining the blood flow in the organ using said input radiofrequency signals of substantially constant envelope.

2. The apparatus of claim 1, wherein said signal processing unit is designed and configured to determine a phase shift of the input radiofrequency signals relative to the output radiofrequency signals of substantially constant envelope, said phase shift being indicative of the blood flow in the organ.

3. The apparatus of claim 1, wherein said envelope elimination unit is designed and configured to maintain a phase modulation of said input radiofrequency signals.

4. The apparatus of claim 1, wherein said envelope elimination unit comprises a limiter amplifier.

5. The apparatus of claim 1, further comprising a mixer, for mixing the output radiofrequency signals and said input radiofrequency signals of substantially constant envelope thereby to provide a mixed radiofrequency signal.

6. The apparatus of claim 5, wherein said electronic circuitry is designed and configured to filter out a portion of said mixed radiofrequency signal so as to substantially increase a signal-to-noise ratio of a remaining portion of said mixed radiofrequency signal.

7. The apparatus of claim 5, wherein said mixer is operable to provide a radiofrequency sum and a radiofrequency difference.

8. The apparatus of claim 7, wherein said electronic circuitry comprises a low pass filter for filtering out said radiofrequency sum.

9. The apparatus of claim 6, wherein said electronic circuitry comprises an analog amplification circuit for amplifying said remaining portion of said mixed radiofrequency signal.

10. The apparatus of claim 6, wherein said signal-to-noise ratio is increased by at least 10 dB.

11. A method of determining blood flow in an organ of a subject from output radiofrequency signals transmitted to the organ and input radiofrequency signals received from the organ, the method comprising:

reducing or eliminating amplitude modulation of said input radiofrequency signals to provide input radiofrequency signals of substantially constant envelope; and

determining the blood flow in the organ using said input radiofrequency signals of substantially constant envelope.

12. The method of claim 11, wherein said reducing or eliminating amplitude modulation comprises maintaining a phase modulation of said input radiofrequency signals.

13. The method of claim 11, further comprising mixing the output radiofrequency signals and said input radiofrequency signals of substantially constant envelope thereby to provide a mixed radiofrequency signal.

14. The method of claim 13, wherein said electronic circuitry is designed and configured to filter out a portion of said mixed radiofrequency signal so as to substantially increase a signal-to-noise ratio of a remaining portion of said mixed radiofrequency signal.

15. The method of claim 13, wherein said mixing comprises providing a radiofrequency sum and a radiofrequency difference.

16. The method of claim 15, further comprising filtering out said radiofrequency sum.

17. The method of claim 14, wherein said signal-to-noise ratio is increased by at least 10 dB.

18. A method of calculating blood flow in an organ of a subject using output radiofrequency signals transmitted to the organ and input radiofrequency signals received from the organ, the method comprising determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals and using said phase shift to calculate the blood flow in the organ.

19. The method of claim 18, wherein said using said phase shift to calculate the blood flow comprises using a linear relationship between said phase shift and the blood flow.

20. The method of claim 19, wherein a proportion coefficient of said linear relationship comprises a systolic ejection time of a heart of the subject.