Claims
- 1. A method of detecting the lumen within a blood vessel, comprising:
transmitting acoustic energy into the blood vessel; evaluating the signal level of reflections of said acoustic energy as a function of propagation of said energy within said blood vessel, and identifying at least one region of reduced signal level within said reflections.
- 2. The method of claim 1, wherein said act of evaluating further comprises demodulating said reflections.
- 3. The method of claim 2, wherein said act of demodulating comprises:
(i) deriving a first frequency component of said reflections; (ii) deriving a second frequency component of said reflections; and (iii) filtering said first and second components to retain only a subset of said first and second frequency components.
- 4. The method of claim 3, wherein said act of deriving a first frequency component comprises multiplying said reflections by a Sine function related to the center frequency of said transmitted acoustic energy, and said act of deriving a second frequency component comprises multiplying said reflections by a Cosine function related to the center frequency of said transmitted acoustic energy.
- 5. The method of claim 4, wherein said act of filtering said first and second components comprises lowpass filtering said components to retain only the difference (baseband) frequency components.
- 6. The method of claim 3, further comprising:
squaring said filtered subset of components to produce a squared parameter; and decimating said squared parameter to a first sampling rate to produce a squared decimated parameter.
- 7. The method of claim 6, further comprising at least one depth-dependent function to said squared decimated parameter, said at least one depth dependent function compensating at least in part for propagation loss of said acoustic energy within said blood vessel.
- 8. The method of claim 2, further comprising:
determining the power in a plurality of propagation intervals; and identifying at least one minima within at least one of said plurality of propagation intervals.
- 9. The method of claim 8, further comprising determining an average value of said at least one minima determined at different points in time within said reflections.
- 10. A method of detecting at least one wall of a blood vessel, comprising:
transmitting acoustic energy into the blood vessel; detecting at least one region associated with the lumen in said blood vessel; and detecting the location of said at least one wall of the blood vessel relative to said lumen; wherein the act of detecting the location comprises analyzing A-mode data derived from said act of transmitting.
- 11. The method of claim 10, wherein the act of detecting the location further comprises:
(i) determining the A-mode signal level associated with said region of said lumen; (ii) detecting at least one region where the A-mode signal level varies between said level associated with said region of said lumen and a higher signal level; and (iii) associating the location of said at least one wall with said at least one region of variation.
- 12. The method of claim 11, wherein the act of detecting at least one region associated with said lumen further comprises demodulating at least a portion of said A-mode signals.
- 13. The method of claim 12, wherein said act of demodulating comprises:
deriving a first frequency component of said A-mode signals; deriving a second frequency component of said A-mode signals; and filtering said first and second components to obtain a baseband component representation of said A-mode signals.
- 14. A method of determining the diameter of a blood vessel, comprising:
transmitting acoustic energy into the blood vessel; detecting the region associated with the lumen in said blood vessel; detecting the location of a first wall of the blood vessel relative to said lumen; detecting the location of a second wall of the blood vessel relative to said lumen; and determining the diameter of at least a portion of said blood vessel based at least in part on said locations of said first and second walls.
- 15. The method of claim 14, wherein said acts of detecting the location each further comprise:
(i) determining the A-mode signal level associated with said region of said lumen; (ii) detecting at least one region where the A-mode signal level varies between said level associated with said region of said lumen and a higher signal level; and (iii) associating the location of said first or second wall with said at least one region of variation.
- 16. The method of claim 15, wherein said first wall comprises a front wall of said blood vessel, and the act of detecting at least one region where the A-mode signal level varies comprises detecting such at least one region at a depth less than that of said lumen.
- 17. A method of assessing hemodynamic properties within the circulatory system of a living subject, comprising:
measuring a first parameter from a blood vessel of said subject; at least partly compressing said blood vessel; measuring a second parameter from said blood vessel during said act of compressing, the act of measuring said second parameter comprising: (i) transmitting an acoustic wave into said blood vessel; (ii) receiving at least one echo of said acoustic wave; and (iii) analyzing said at least one echo to derive an estimate of the diameter of said blood vessel; deriving a calibration function based at least in part on said second parameter; and calibrating the first parameter using said calibration function.
- 18. The method of claim 17, wherein the act of deriving a calibration function comprises:
identifying at least one artifact within said second parameter; and generating a calibration function based on said at least one artifact.
- 19. An apparatus for measuring hemodynamic properties within the blood vessel of a living subject comprising:
a first transducer adapted to measure at least a first hemodynamic parameter associated with said blood vessel; a second transducer adapted to transmit ultrasonic energy into said blood vessel and receive echoes therefrom; and a signal processor operatively connected to said second transducer and configured to detect the lumen within said blood vessel based on said echoes, and estimate the diameter of said blood vessel based thereon, said estimate of diameter of said blood vessel being used at least in part to calibrate said measurement of said first hemodynamic parameter.
- 20. The apparatus of claim 19, further comprising an applanation device adapted to compress said blood vessel while measuring said second hemodynamic parameter.
- 21. The apparatus of claim 20, wherein said blood vessel comprises the radial artery of a human being.
- 22. The apparatus of claim 21, wherein said first transducer comprises a pressure transducer disposed in proximity to said radial artery, and said second transducer comprises an ultrasonic transducer also disposed in proximity to said radial artery.
- 23. The apparatus of claim 22, wherein said processor is adapted to analyze A-mode signals derived from said echoes.
- 24. An information storage device, comprising;
a data storage medium; a plurality of data stored on said medium, said plurality of data comprising a computer program adapted to run on a data processor, said computer program being configured for determining a first hemodynamic parameter of a living subject based on first input data, the act of determining said first hemodynamic parameter comprising:
analyzing said first input data to identify the location of a first artifact therein; analyzing said first input data to identify the location of at least one second artifact therein, the location of said at least one second artifact being related to that of said first artifact; and determining said first hemodynamic parameter based on said locations of said first and said at least one second artifacts.
- 25. The storage device of claim 24, wherein said location of said first artifact comprises the location of the lumen within a blood vessel of said living subject.
- 26. The storage device of claim 25, wherein said location of said at least one second artifact comprises the location of the front and rear walls of said blood vessel relative to said lumen, and said first hemodynamic parameter comprises the diameter of said blood vessel.
- 27. The storage device of claim 24, wherein said act of analyzing said first input data to identify the location of said first artifact comprises identifying at least one minimum within the signal level of reflected acoustic energy.
- 28. A method of providing treatment to a living subject, comprising:
selecting a blood vessel of said subject useful for measuring pressure data; measuring pressure data from said selected blood vessel non-invasively; measuring a hemodynamic parameter from said blood vessel by detecting the relative locations of the lumen within said blood vessel and at least one wall thereof; generating a calibration function from data obtained from said measuring of said hemodynamic parameter; applying said calibration function to said pressure data to produce a representation of blood pressure within said blood vessel; and providing treatment to said subject based on said representation.
- 29. The method of claim 28, wherein said blood vessel is the radial artery of a human being, and the act of measuring pressure data comprises obtaining a pressure waveform using a sensor applied at the skin proximate to said radial artery.
- 30. The method of claim 29, wherein the act of measuring a hemodynamic parameter comprises:
generating acoustic waves; transmitting said acoustic waves into said radial artery; receiving echoes of said acoustic wave; analyzing said echoes to detect the location of said lumen; detecting the location of at least one artery wall based on said act of detecting said lumen; and determining the diameter of said artery based on said location of said lumen and said at least one artery wall.
- 31. A method of determining the actual value of a first parameter within the circulatory system of a living subject, comprising:
measuring the value of a first parameter associated with the circulatory system non-invasively, the measured value of the first parameter being different from the actual value thereof; applying a stress on the circulatory system to alter the hemodynamic properties thereof; the application of said stress being determined at least in part by detecting the location of the lumen within at least one blood vessel of said circulatory system; measuring a second parameter associated with the circulatory system while the stress is applied; generating a calibration function based at least in part on the measured second parameter; and correcting the measured first parameter using the calibration function.
- 32. A method of determining the actual value of a first parameter within the circulatory system of a living subject, comprising:
measuring the value of a first parameter associated with the circulatory system non-invasively, the measured value of the first parameter being different from the actual value thereof; applying a stress on the circulatory system to alter the hemodynamic properties thereof; the application of said stress being determined at least in part by detecting the location of the lumen within at least one blood vessel of said circulatory system; measuring a second parameter associated with the circulatory system while the stress is applied; measuring a third parameter associated with the circulatory system; generating a calibration function based at least in part on the measured second parameter; and correcting the measured first parameter using the calibration function.
- 33. The method of claim 32, wherein:
(i) the act of measuring said first parameter comprises measuring the pressure in at least a portion of said circulatory system; (ii) the act of measuring said second parameter comprises measuring the diameter of said at least portion of said circulatory system; and (iii) the act of measuring said third parameter comprises measuring the velocity or kinetic energy of blood flowing within said lumen.
- 34. A method of assessing the arterial blood pressure of a living subject, comprising:
applanating said blood vessel at least partly; measuring the diameter of said blood vessel during said act of applanating; measuring the pressure applied to said blood vessel as a function of time during said at least a portion of said act of applanating in order to produce a pressure waveform; identifying at least one artifact within said pressure waveform; and using said at least one artifact to determine said arterial blood pressure.
- 35. The method of claim 34, wherein the act of identifying at least one artifact comprises:
setting lower and upper pressure limits to define a region of interest; and identifying at least one portion within said region of interest wherein the slope of said pressure waveform as measured over a predetermined interval meets a predetermined criterion.
- 36. The method of claim 35, wherein said act of applanating comprises maintaining the pressure applied during said act of applanating within a predetermined band, said predetermined band being determined at least in part based on said at least one portion.
- 37. The method of claim 36, wherein the act of measuring the diameter comprises analyzing backscattered ultrasonic energy, and detecting at least one region of reduced reflected energy therein.
- 38. A method of detecting at least one wall of a blood vessel, comprising:
transmitting acoustic energy into the blood vessel; determining the power of reflections of said acoustic energy as a function of the depth within said blood vessel, and identifying at least one first artifact within said power, said at least one artifact being related to the lumen associated with said blood vessel; and identifying at least one second artifact within wall of said blood vessel based at least in part on said first artifact and said act of determining the power.
- 39. A method of scaling a hemodynamic parameter, comprising:
providing a reference waveform; generating an uncorrected waveform including said hemodynamic parameter; determining at least one correction for said uncorrected waveform based at least in part on said reference waveform; and applying said correction to said uncorrected waveform to scale same.
- 40. The method of claim 39, further comprising calculating a transfer function based at least in part on said uncorrected waveform and said scaled waveform.
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/534,900 entitled “Method And Apparatus For Assessing Hemodynamic Properties within the Circulatory System of a Living Subject” filed Mar. 23, 2000, and assigned to the Assignee hereof, and incorporated by reference herein in its entirety.
[0002] This application is related to U.S. patent application Ser. No. ______ entitled “Method And Apparatus For The Noninvasive Assessment Of Hemodynamic Parameters Including Blood Vessel Location” filed contemporaneously herewith, assigned to the Assignee hereof.
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
09534900 |
Mar 2000 |
US |
Child |
09815080 |
Mar 2001 |
US |