Non-invasive determination of blood components

• US 20030002722A1
• Filed: 04/04/2002
• Published: 01/02/2003
• Est. Priority Date: 04/05/2001
• Status: Active Grant

• Current Assignee: Rhode Island Hospital
• Original Assignee: Rhode Island Hospital
• Inventors: Jay, Gregory D., Ernsting, Kevin S., Suner, Selim
• Granted Patent: US 7,711,403 B2
• Time in Patent Office: Days
• US Class Current: 382/128
• CPC Class Codes: A61B 2560/0233 Optical standards
• CPC Class Codes: A61B 3/14 Arrangements specially adapted for eye photography apparatus or arrangements for taking photographs per se G03B
• 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 5/1034 by means of colour cards
• 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 5/443 Evaluating skin constituents, e.g. elastin, melanin, water

Abstract

A method of estimating an amount of a substance in a bodily fluid from the color of a tissue surface of a subject includes capturing an image including at least a portion-of-interest of the subject and at least a reference portion of a color reference, the image being a digital image of pixels of at least one color, the image including a component value for each pixel for each of the at least one color, obtaining a first value associated with at least one component value corresponding to the portion-of-interest of the subject, obtaining a second value associated with at least one component value corresponding to the reference portion, and calculating an estimated amount of the substance using the first and second values.

Claims

1. A method of estimating an amount of a substance in a bodily fluid from the color of a tissue surface of a subject, the method comprising:

capturing an image including at least a portion-of-interest of the subject and at least a reference portion of a color reference, the image being a digital image of pixels of at least one color, the image including a component value for each pixel for each of the at least one color;

obtaining a first value associated with at least one component value corresponding to the portion-of-interest of the subject;

obtaining a second value associated with at least one component value corresponding to the reference portion; and

calculating an estimated amount of the substance using the first and second values.

2. The method of claim 1 wherein the image comprises a plurality of colors for each pixel, wherein obtaining the first value comprises obtaining a plurality of first values each associated with at least one component value of a corresponding color, wherein obtaining the second value comprises obtaining a plurality of second values each associated with at least one component value of a corresponding color, and wherein the calculating the estimated amount uses each of the plurality of first and second values.

3. The method of claim 2 wherein obtaining the first and second values comprises averaging component values in a first portion of the portion-of-interest and a second portion of the reference portion, respectively, for each of the plurality of colors.

4. The method of claim 3 wherein the calculating comprises using first and second empirically-predetermined weighting constants associated with the first and second values respectively.

5. The method of claim 1 further comprising selecting a first portion of the portion-of-interest and a second portion of the color reference, and wherein the first and second values are obtained from at least one component value of each of the first and second portions, respectively.

6. The method of claim 5 wherein the first portion is a biologically perfused surface of the subject.

7. The method of claim 6 wherein the capturing is performed non-invasively.

8. The method of claim 1 wherein the capturing, the obtaining a first value, the obtaining a second value, and the calculating are performed in real time.

9. The method of claim 1 wherein the obtaining a first value, the obtaining a second value, and the calculating are at least partially performed by a processor executing software instructions.

10. The method of claim 1 wherein the portion-of-interest is a conjunctiva and the amount of the substance is a hemoglobin concentration.

11. The method of claim 1 further comprising displaying the estimated amount.

12. The method of claim 11 wherein the estimated amount is a hemoglobin concentration and is displayed in units of grams per deciliter (g/dl).

14. The method of claim 13 further comprising repeating the calculating, the comparing, and the adjusting until the estimated amount of the substance has the desired relationship with the known amount of the substance.

15. The method of claim 14 further comprising storing the first and second factors when the estimated amount of the substance has the desired relationship with the known amount of the substance.

16. The method of claim 13 wherein the image comprises a plurality of colors for each pixel, wherein the establishing establishes a plurality of first factors and a plurality of second factors each corresponding to a respective one of the plurality of colors, wherein the calculating the estimated amount uses each of the first and second factors, and wherein the adjusting adjusts any of the first and second factors.

17. The method of claim 13 further comprising selecting a first region of the portion-of-interest and a second region of the reference color.

18. The method of claim 17 wherein the calculating uses averages of the component values for each color over the first and second regions, respectively.

19. The method of claim 18 wherein the calculating uses ratios of the averages of the component values for each color over the first and second regions, respectively.

13. A method of determining factors that influence estimation of an amount of a substance in a bodily fluid from the color of a tissue surface of a subject, the method comprising:

capturing an image including at least a portion-of-interest of the subject and at least a reference portion of a color reference, the image being a digital image of pixels of at least one color, the image including a component value for each pixel for each of the at least one color;

establishing a first factor associated with the portion-of-interest and a second factor associated with the reference portion;

calculating an estimated amount of the substance in the subject using the component values and the first and second factors;

comparing the estimated amount with a corresponding known amount of the substance in the subject; and

adjusting, if the estimated amount has other than a desired relationship with the known amount, at least one of the first and second factors.

20. A system for determining a level of a substance in a bodily fluid from the color of a tissue surface, the system comprising:

a color separator module configured to decompose a digital color image of a perfused surface of a subject and a color reference object into sub-images of component colors, the sub-images comprising digital component values corresponding to pixels of the image;

a portion selector module in communication with the color separator module and configured to select a first window of the image of the perfused surface and to select a second window of the image of the color reference object; and

a substance estimator module in communication with the portion selector and configured to calculate an estimated level of the substance using window values associated with component values corresponding to the first and second windows.

21. The system of claim 20 further comprising an imaging module configured to capture the image and to convey the digital component values of the image to the color separator module.

22. The system of claim 21 wherein the imaging module is configured to capture the image non-invasively.

23. The system of claim 20 wherein the portion selector module is further configured to average the component values of each sub-image to produce the window values, with one window value for each sub image for each of the first and second windows.

24. The system of claim 20 wherein the color separator module, the portion selector module, and the substance estimator module each comprise computer-executable instructions, stored on a computer-readable medium, for causing a computer to perform actions as recited in claim 20.

25. The system of claim 20 further comprising a display coupled to the substance estimator module and configured to display indicia of the estimated level of the substance.