Method and apparatus for determining one or more blood parameters from analog electrical signals

• US 8,708,907 B2
• Filed: 05/05/2010
• Issued: 04/29/2014
• Est. Priority Date: 05/06/2009
• Status: Active Grant

• Current Assignee: Elfi-Tech Ltd
• Original Assignee: Elfi-Tech
• Inventors: Fine, Ilya, Kaminsky, Alexander
• Primary Examiner(s): Cheng, Jacqueline
• Assistant Examiner(s): Agahi, Puya
• Application Number:
  US12/774,056
• Publication Number:
  US 20100286497A1
• Time in Patent Office: 1,455 Days
• Field of Search: 600/368, 600/369, 600/301, 600/323, 600/324, 600/336, 600/364, 600/465, 600/467, 600/468, 600/504
• US Class Current: 600/369
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/02241 of small dimensions, e.g. adapted to fingers
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

Embodiments of the present invention relate to a system and method for in vivo measurement of blood parameters by processing analog electrical signals from a plurality of photodetectors. In some embodiments, it is possible to determine one or more blood parameters according to (i) a first electrical signal from a first detector and (ii) a second electrical signal from a second photodetector. A difference analog electrical signal is generated, indicative of a difference between the light response signal at the first location and light response signal at the second location, is generated. One or more blood parameters may be detected according to the difference analog electrical signal.

Claims

1. A method for obtaining physiological information from a subject in accordance with a light field whose intensity varies according to location, the method comprising:

a) applying partially or entirely coherent light to a target region of the subject to induce a light response signal from the illuminated target region which contributes to a location-dependent light field LF(x, y, z);

b) detecting the light field LF(x₁, y₁, z₁) prevailing at a first location (x₁, y₁, z₁) to generate a first analog electrical signal A₁(t), the first analog electrical signal A₁(t) including a dynamic light scattering (DLS) component DLS(A₁(t)) that is indicative of a first DLS measurement;

c) detecting the light field signal LF(x₂, y₂, z₂) prevailing at a second location (x₂, y₂, z₂) to generate a second analog electrical signal A₂(t), the second analog electrical signal A₂(t) including a DLS component DLS(A₂(t)) that is indicative of a second DLS measurement and that is uncorrelated with the DLS component of the first analog signal A₁(t);

d) processing, by analog electrical circuitry, the first and second analog electrical signals to generate a processed analog electrical signal processed(t) from a difference between the first and second analog electrical signals, wherein;

(i) a first DLS contribution ratio

2. The method of claim 1 further comprising:

e) digitizing the processed analog signal to generate a digital signal indicative of a combination of the first and second dynamic scattering measurements;

f) processing the indicative digital signal to compute at least one physiological parameter.

3. The method of claim 2 wherein the computing includes computing at least one of a blood velocity, a blood rheological parameter, a blood pressure, a heartbeat, a blood oxygen concentration, and a pulse.

4. The method of claim 1 further comprising:

e) before the light field detecting, inducing a change in blood flow at or near the target region.

5. The method of claim 4 wherein the blood flow change inducing is carried out by applying a force or a pressure to the subject.

6. The method of claim 5 wherein the target region is located in a location selected from the group consisting of a finger region, a back region, a leg region, a face region and an arm region.

7. The method of claim 1 wherein a ratio between an intensity, at a wavelength of the at least partially coherent light, of the detected light field signal prevailing at the first location and intensity, at a wavelength of the at least partially coherent light, of the detected light field signal prevailing at the second location is between 0.95 and 1.05.

8. The method of claim 1 wherein the detecting at the first and second locations is performed respectively by first and second photodetectors.

9. The method of claim 8 wherein the first and second photodetectors are separated from each other by a separation distance that is at least 0.5 mm and at most 2 cm.

10. The method of claim 2 wherein the computing includes computing a blood rheological parameter.

11. The method of claim 2 wherein the computing includes computing a blood pressure.

12. The method of claim 2 wherein the computing includes computing a pulse.