Method and apparatus for assessing hemodynamic parameters within the circulatory system of a living subject

• US 20060206032A1
• Filed: 05/18/2006
• Published: 09/14/2006
• Est. Priority Date: 03/23/2000
• Status: Active Grant

• Current Assignee: Frank R. Miele, Ronald Mucci, Stuart L. Gallant
• Original Assignee: Frank R. Miele, Ronald Mucci, Stuart L. Gallant
• Inventors: Gallant, Stuart L., Miele, Frank R., Mucci, Ronald
• Granted Patent: US 8,328,727 B2
• Time in Patent Office: Days
• US Class Current: 600/504
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• 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
• CPC Class Codes: A61B 8/0858 involving measuring tissue layers, e.g. skin, interfaces

Abstract

An improved method and apparatus for non-invasively assessing one or more hemodynamic parameters associated with the circulatory system of a living organism. In one aspect, the invention comprises a method of measuring a hemodynamic parameter by measuring a non-calibrated value of the parameter non-invasively, and inducing a stress of the circulatory system while measuring a second parameter. The response of the circulatory system to the stress is determined directly from the subject, and a calibration function is derived from the response and applied to the non-calibrated measured value to produce a calibrated measure of the actual value of the hemodynamic parameter. Methods of using backscattered acoustic energy for determination of hemodynamic markers are also disclosed.

Claims

1-40. -40. (canceled)

41. A method of locating a blood vessel having a lumen, comprising:

transmitting acoustic energy into the blood vessel;

receiving a signal related to reflections of said acoustic energy;

identifying at least one artifact associated with said lumen in said received signal, said at least one artifact corresponding to a first location;

computing a power function in a first direction from said first location; and

computing a power function in a second direction from said first location;

wherein said acts of computing substantially determine the location of said blood vessel.

42. The method of claim 41, wherein said act of transmitting is performed using an ultrasonic transducer.

43. The method of claim 42, wherein said act of identifying further comprises computing the average power within a predetermined distance interval along an A-mode line.

44. The method of claim 41, wherein said act of identifying comprises using signal processing algorithms comprising:

basebanding said signal to produce a basebanded signal; and

squaring the basebanded signal to produce envelope-squared data.

45. The method of claim 44, wherein said act of basebanding comprises:

multiplying the received signal by a sine and cosine function to produce a multiplied signal; and

lowpass filtering said multiplied signal to produce said basebanded signal.

46. The method of claim 44, wherein said acts of computing further comprise decimating said envelope-squared data to a predetermined sampling rate, and applying a depth-dependent gain to said decimated envelope-squared data.

47. The method of claim 46, wherein said depth-dependent gain is non-linear.

48. A method of locating a blood vessel having a lumen, comprising:

transmitting acoustic energy into said blood vessel;

receiving backscattered energy derived from said transmitted acoustic energy;

processing said backscattered energy to detect a location of said lumen; and

detecting the location of one or more walls associated with said lumen.

49. The method of claim 48, wherein said act of processing is performed using a plateau-based method.

50. The method of claim 49, wherein said plateau-based method comprises:

determining a power metric as a function of depth;

integrating said power metric and normalizing said integrated power metric to unity;

dividing said normalized integrated power metric into a predetermined number of intervals; and

detecting a plateau associated with said lumen based at least in part on said acts of determining, integrating and dividing.

51. The method of claim 50, wherein said act of dividing is performed in substantially equally spaced intervals.

52. The method of claim 50, wherein said act of dividing is performed in substantially non-equally spaced intervals.

53. The method of claim 50, wherein said act of processing is performed using an interval-based method.

54. Apparatus adapted to detect the location of a blood vessel, comprising:

an acoustic transducer;

a signal transceiver operatively coupled to said acoustic transducer; and

a processor operatively coupled to said signal transceiver, said processor adapted to perform computations on data received by said signal transceiver in order to compute the location of said blood vessel.

55. The apparatus of claim 54, wherein said acoustic transducer comprises an ultrasonic transducer.

56. The apparatus of claim 55, wherein said processor is adapted to compute the average power within a predetermined distance interval along an A-mode line, said A-mode line associated with the data received by said signal transceiver.

57. The apparatus of claim 54, wherein said processor is adapted to:

baseband said received acoustic energy data; and

square the basebanded data to produce an envelope-squared data.

58. The apparatus of claim 57, wherein said processor performs said basebanding according to the method comprising:

multiplying the received acoustic energy data by a sine and cosine function; and

lowpass filtering said multiplied data to produce said basebanded data.

59. The apparatus of claim 57, wherein said processor is further adapted to decimate said envelope-squared data to a predetermined sampling rate, and apply a depth-dependent gain to said decimated envelope-squared data.

60. The apparatus of claim 59, wherein said depth-dependent gain is non-linear.

61. An apparatus adapted to detect and display the location of a blood vessel, comprising:

an acoustic transducer adapted to be positioned proximate said blood vessel;

a digital processor having a computer program operative to run thereon, said processor and program adapted to;

process acoustical backscatter energy data received from said acoustic transducer; and

output data comprising a location of said blood vessel; and

a display, said display adapted to display said location of said blood vessel based at least in part on said data from said digital processor.

62. The apparatus of claim 61, wherein said acoustic transducer comprises an ultrasonic transducer.

63. The apparatus of claim 61, wherein said processor is adapted to process said acoustical backscatter energy data to locate the position of said blood vessel by the method comprising:

determining a lumen location; and

based at least in part on said lumen location, detecting one or more blood vessel wall locations.

64. The apparatus of claim 63, wherein said act of detecting is performed using a plateau-based method.

65. The apparatus of claim 63, wherein said act of detecting is performed using an interval-based method.

66. An apparatus for locating the position of a blood vessel having a lumen, said apparatus locating said position according to the method, comprising:

transmitting acoustic energy into the blood vessel;

determining the power of backscatter energy from said transmitted energy as a function of the depth within said blood vessel;

identifying at least one artifact associated with a location of said lumen;

computing a power function in a first dimension relative to said location; and

computing a power function in a second dimension relative to said location;

wherein said acts of computing substantially determine the location of said blood vessel.

67. The apparatus of claim 66, wherein said act of identifying is performed using a method that identifies at least one plateau.

68. The apparatus of claim 66, wherein said act of identifying is performed using a method that specifies at least one interval.

69. An apparatus for locating the depth of a blood vessel, said act of locating performed according to the method, comprising:

transmitting acoustic energy into said blood vessel;

receiving a reflected energy from said transmitted acoustic energy;

processing said reflected energy to identify a lumen;

repeating said acts of transmission and reception at least once to produce at least one repeated reception; and

processing said at least one repeated reception to identify at least one wall of said blood vessel.

70. The apparatus of claim 69, wherein said processing of said at least one repeated reception is performed to determine the depth of the at least one wall of said blood vessel.

71. The apparatus of claim 69, further comprising setting a threshold value for both a front wall and a back wall of said blood vessel.

72. The apparatus of claim 71, wherein said front wall threshold value comprises a function of said back wall threshold value.

73. The apparatus of claim 69, wherein said act of processing said at least one repeated reception further comprises using a weighting system, said weighting system assigning a score to an A-mode signal should a signal level exceed a predetermined value.

74. The apparatus of claim 73, wherein said A-mode signal further comprises an envelope-squared value.

75. The apparatus of claim 73, wherein said A-mode signal further comprises an integrated power value.

76. The apparatus of claim 69, wherein said act of processing said at least one repeated reception comprises applying a weighting system, said weighting system being determined at least in part based on a depth of one or more detected artifacts.

77. Apparatus adapted to non-invasively detect the location of a blood vessel, and further determine a pressure therefrom, comprising:

an acoustic transducer;

a pressure sensor substantially proximate to said transducer;

a signal transceiver in signal communication with said acoustic transducer; and

a processor operatively coupled to said signal transceiver and said sensor, said processor adapted to;

perform computations on signals received by said signal transceiver in order to determine the proper placement of said pressure sensor with respect to said vessel;

cause adjustment of the placement of said sensor based at least in part on said determination of the proper placement; and

perform computations on signals generated by said pressure sensor after said proper placement to determine said pressure.