Determination of a measure of a glycation end-product or disease state using tissue fluorescence

• US 20050148834A1
• Filed: 10/22/2004
• Published: 07/07/2005
• Est. Priority Date: 04/04/2002
• Status: Active Grant

• Current Assignee: Veralight, Inc. (Britannia Life Sciences, Inc.)
• Original Assignee: Veralight, Inc. (Britannia Life Sciences, Inc.)
• Inventors: Maynard, John D., Johnson, Robert D., Brown, Christopher D., Ediger, Marwood Neal, Hull, Edward L.
• Granted Patent: US 7,139,598 B2
• Time in Patent Office: Days
• US Class Current: 600/317
• 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 5/0064 Body surface scanning
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/0068 Confocal scanning
• CPC Class Codes: A61B 5/0071 by measuring fluorescence emission
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/441 Skin evaluation, e.g. for skin disorder diagnosis

Abstract

A method of determining a measure of a tissue state (e.g., glycation end-product or disease state) in an individual. A portion of the tissue of the individual is illuminated with excitation light, then light emitted by the tissue due to fluorescence of a chemical with the tissue responsive to the excitation light is detected. The detected light can be combined with a model relating fluorescence with a measure of tissue state to determine a tissue state. The invention can comprise single wavelength excitation light, scanning of excitation light (illuminating the tissue at a plurality of wavelengths), detection at a single wavelength, scanning of detection wavelengths (detecting emitted light at a plurality of wavelengths), and combinations thereof. The invention also can comprise correction techniques that reduce determination errors due to detection of light other than that from fluorescence of a chemical in the tissue. For example, the reflectance of the tissue can lead to errors if appropriate correction is not employed. The invention can also comprise a variety of models relating fluorescence to a measure of tissue state, including a variety of methods for generating such models. Other biologic information can be used in combination with the fluorescence properties to aid in the determination of a measure of tissue state. The invention also comprises apparatuses suitable for carrying out the method, including appropriate light sources, detectors, and models (for example, implemented on computers) used to relate detected fluorescence and a measure of tissue state.

Claims

1. A method of determining a tissue state of the tissue of an individual, comprising:

a. Illuminating a portion of the tissue of the individual with excitation light;

b. Detecting light emitted from the tissue by fluorescence of a chemical within the tissue;

c. Determining the measure of chemical change from the detected light and a model relating fluorescence and a tissue state.

2. A method as in claim 1, wherein the excitation light has a wavelength in the range from 280 nm to 500 nm.

3. A method as in claim 2, wherein the excitation light has a wavelength in the range from 315 nm to 500 nm.

4. A method as in claim 1, wherein the excitation light has a first wavelength at a first time, and a second wavelength, different from the first wavelength, at a second time.

5. A method as in claim 1, wherein detecting light emitted from the tissue comprises detecting light at a wavelength greater than the excitation light wavelength.

6. A method as in claim 1, wherein detecting light emitted from the tissue comprises detecting light at a wavelength between 250 nm and 850 nm.

7. A method as in claim 1, wherein detecting light emitted from the tissue comprises detecting light at each of a plurality of wavelengths.

8. A method as in claim 7, wherein the excitation light has a single wavelength, and wherein detecting light emitted from the tissue comprises detecting light at a plurality of wavelengths.

9. A method as in claim 1, wherein the excitation light wavelength varies with time, and wherein detecting light emitted from the tissue comprises detecting light at a first wavelength.

10. A method as in claim 1, wherein detecting light emitted from the tissue comprises:

a. Determining a tissue reflectance characteristic at an excitation light wavelength;

b. Detecting light returned from the tissue in response to illumination at the excitation wavelength;

c. Determining a corrected fluorescence measurement from the detected light and the tissue reflectance characteristic;

d. And wherein determining a tissue state comprises determining the tissue state from the corrected fluorescence measurement and a model relating fluorescence and tissue state.

11. A method as in claim 1, wherein detecting light emitted from the tissue comprises:

a. Determining a tissue reflectance characteristic at a detection wavelength;

b. Detecting light at the detection wavelength returned from the tissue in response to illumination;

c. Determining a corrected fluorescence measurement from the detected light and the tissue reflectance characteristic;

d. And wherein determining a tissue state comprises determining the tissue state from the corrected fluorescence measurement and a model relating fluorescence and tissue state.

12. A method as in claim 1, wherein detecting light emitted from the tissue comprises:

a. Determining a first tissue reflectance characteristic at an excitation light wavelength;

b. Determining a second tissue reflectance characteristic at a detection wavelength;

c. Detecting light at the detection wavelength returned from the skin in response to illumination at the excitation wavelength;

d. Determining a corrected fluorescence measurement from the detected light and the first and second tissue reflectance characteristics;

e. And wherein determining a tissue state comprises determining the tissue state from the corrected fluorescence measurement and a model relating fluorescence and tissue state.

13. A method as in claim 10, wherein determining a tissue reflectance characteristic comprises:

a. illuminating the tissue with reflectance illumination light having an excitation wavelength;

b. detecting reflectance light having the excitation wavelength reflected from the skin, using the same detector as used to detect light returned from the tissue; and

c. establishing a tissue reflectance characteristic from a relationship between the reflectance illumination light and the reflectance light.

14. A method as in claim 10, wherein determining a tissue reflectance characteristic comprises:

a. illuminating the portion of the tissue with reflectance illumination light having an excitation wavelength;

b. detecting reflectance light having the excitation wavelength reflected from the portion of the skin; and

c. establishing a tissue reflectance characteristic from a relationship between the reflectance illumination light and the reflectance light.

15. A method as in claim 11, wherein determining a tissue reflectance characteristic comprises:

a. illuminating the tissue with reflectance illumination light having a wavelength the same as the detection wavelength;

b. detecting reflectance light having the detection wavelength reflected from the skin, using the same detector as used to detect light returned from the tissue; and

c. establishing a tissue reflectance characteristic from a relationship between the reflectance illumination light and the reflectance light.

16. A method as in claim 11, wherein determining a tissue reflectance characteristic comprises:

a. illuminating the portion of the tissue with reflectance illumination light having a wavelength the same as the detection wavelength;

b. detecting reflectance light having the detection wavelength reflected from the portion of the skin; and

c. establishing a tissue reflectance characteristic from a relationship between the reflectance illumination light and the reflectance light.

17. A method as in claim 1, wherein detecting light comprises determining a relationship between an excitation wavelength and fluorescence at a detection wavelength, and wherein determining a measure of chemical change due to glycemic control comprises comparing the relationship with a model defining a relationship between a measure of chemical change and relationships between the excitation wavelength and fluorescence at the detection wavelength.

18. A method as in claim 17, wherein detecting light comprises determining a relationship between illumination at a plurality of excitation wavelengths and fluorescence at a detection wavelength, and wherein determining a measure of chemical change due to glycemic control comprises comparing the relationship with a model defining a relationship between a measure of chemical change and relationships between the plurality of excitation wavelengths and fluorescence at the detection wavelength.

19. A method as in claim 17, wherein detecting light comprises determining a relationship between illumination at an excitation wavelength and fluorescence at a plurality of detection wavelengths, and wherein determining a measure of chemical change due to glycemic control comprises comparing the relationship with a model defining a relationship between a measure of chemical change and relationships between the excitation wavelength and fluorescence at the plurality of detection wavelengths.

20. A method as in claim 17, wherein detecting light comprises determining a relationship between illumination at a plurality of excitation wavelengths and fluorescence at a plurality of detection wavelength, and wherein determining a measure of chemical change due to glycemic control comprises comparing the relationship with a model defining a relationship between a measure of chemical change and relationships between the plurality of excitation wavelengths and fluorescence at the plurality of detection wavelength.

21. A method as in claim 1, further comprising acquiring biologic information relating to the individual, and wherein determining a tissue state comprises determining the tissue state from the information, the detected light, and a model relating biologic information, fluorescence and tissue state.

22. A method as in claim 21, wherein the biologic information comprises age of the individual, height of the individual, weight of the individual, history of disease in the individual'"'"'s family, ethnicity, skin melanin content, or a combination thereof.

23. A method as in claim 1, wherein the tissue comprises the skin of the individual.

24. A method as in claim 1, wherein the model is determined according to:

a. For each of a plurality of subjects;

i. Determining a fluorescence property of a portion of the tissue of the subject;

ii. Determining a tissue state of the subject;

b. Applying a multivariate method to the plurality of fluorescence property determinations and associated tissue state determinations to generate a model relating fluorescence property to a tissue state.

46. A method according to claim 1, wherein the tissue state comprises the presence of glycation end-products, the concentration of glycation end-products, the change in the concentration of glycation end-products, the presence of glycated collagen, the concentration of glycated collagen, the change in the concentration of glycated collagen, the disease state of the individual, or a combination thereof.

25. A method of determining a tissue state in an individual, comprising:

a. Establishing an interface between an optical system and a portion of the skin of the individual;

b. Determining a relationship of illumination light at an excitation wavelength and the response of the skin at a detection wavelength for each of a plurality of pairings of excitation wavelength and detection wavelength;

c. Determining a tissue reflectance property of the skin at each of the illumination wavelengths and at each of the detection wavelengths;

d. Determining a measure of the intrinsic fluorescence of the skin from the relationships of illumination light and detected light and the tissue reflectance properties;

e. Determining the tissue state of the individual from the intrinsic fluorescence using a model relating intrinsic fluorescence and tissue state.

26. A method as in claim 25, further comprising acquiring biologic information relating to the subject, and wherein determining a tissue state comprises determining the tissue state from the information, the detected light, and a model relating biologic information, fluorescence and tissue state.

27. A method as in claim 26, wherein the biologic information comprises information from Raman spectroscopic investigation of the subject.

28. A method as in claim 26, wherein the biologic information comprises age of the individual, height of the individual, weight of the individual, history of disease in the individual'"'"'s family, ethnicity, skin melanin content, blood HDL cholesterol level of the subject, blood LDL cholesterol level of the subject, blood triglycerides level of the subject, laser-Doppler information from the subject'"'"'s tissue, or a combination thereof.

29. A method of determining a model relating fluorescence and tissue state, comprising:

a. For each of a plurality of subjects;

i. Determining a fluorescence property of a portion of the tissue of the subject;

ii. Determining a tissue state of the subject;

b. Applying a multivariate method to the plurality of fluorescence property determinations and associated tissue state determinations to generate a model relating fluorescence property to tissue state.

30. A method as in claim 29, wherein determining a fluorescence property comprises determining an intrinsic fluorescence of the portion of the tissue.

31. A method as in claim 29, wherein determining a fluorescence property comprises determining an intrinsic fluorescence of the portion of the tissue at each of a plurality of detection wavelengths responsive to excitation light having an excitation wavelength.

32. A method as in claim 29, wherein determining a fluorescence property comprises determining an intrinsic fluorescence of the portion of the tissue at a detection wavelength responsive to excitation light at a plurality of excitation wavelengths.

33. A method as in claim 29, wherein determining a fluorescence property comprises determining an intrinsic fluorescence of the portion of the tissue at pairings of a plurality of detection wavelengths and a plurality of excitation wavelengths.

34. A method as in claim 29, wherein determining a fluorescence property of a portion of the tissue of the subject comprises:

a. Illuminating the portion of the tissue of the individual with excitation light;

b. Detecting light emitted from the tissue by fluorescence of a chemical within the tissue;

35. A method as in claim 34, wherein detecting light emitted from the tissue comprises:

a. Determining a tissue reflectance characteristic at an excitation light wavelength;

b. Detecting light returned from the tissue in response to illumination at the excitation wavelength;

c. Determining a corrected fluorescence measurement from the detected light and the tissue reflectance characteristic.

36. A method as in claim 34, wherein detecting light emitted from the tissue comprises:

a. Determining a tissue reflectance characteristic at a detection wavelength;

b. Detecting light at the detection wavelength returned from the tissue in response to illumination;

c. Determining a corrected fluorescence measurement from the detected light and the tissue reflectance characteristic.

37. A method as in claim 34, wherein detecting light emitted from the tissue comprises:

a. Determining a first tissue reflectance characteristic at an excitation light wavelength;

b. Determining a second tissue reflectance characteristic at a detection wavelength;

c. Detecting light at the detection wavelength returned from the skin in response to illumination at the excitation wavelength;

d. Determining a corrected fluorescence measurement from the detected light and the first and second tissue reflectance characteristics.

38. A method as in claim 29, wherein determining a tissue state comprises at least one of:

a. Evaluating the subject according to an OGTT;

b. Evaluating the subject according to an FPG;

c. Evaluating the subject according to an HbA1c test;

d. Evaluating the subject according to observed symptoms of disease state;

e. Determining the presence or extent of complications associated with the disease state;

f. Determining a previous disease state determination;

g. Determining a level of glycation endproducts in the tissue of the subject.

39. A method as in claim 29, wherein applying a multivariate method comprises applying a multivariate model constructed according to the Partial Least Squares, Principal Components Regression, Classical Least Squares, Multiple Linear Regression, Ridge Regression algorithms, or a combination thereof.

40. A method as in claim 29, wherein the portion of the tissue comprises the skin of the subject.

41. An apparatus for the determination of a tissue state in an individual, comprising:

a. An illumination subsystem;

b. A detection subsystem;

c. An analysis subsystem, comprising a model relating fluorescence property of the skin of an individual to tissue state.

42. An apparatus as in claim 41, wherein the model is determined according to:

a. For each of a plurality of subjects;

i. Determining a fluorescence property of a portion of the tissue of the subject;

ii. Determining a tissue state of the subject;

b. Applying a multivariate method to the plurality of fluorescence property determinations and associated tissue state determinations to generate a model relating fluorescence property to tissue state.

43. A method of determining a tissue state in an individual, comprising:

a. Determining a fluorescence property of a portion of the skin of the individual;

b. Using a multivariate method to determine a tissue state of the individual from the fluorescence property.

44. A method according to claim 43, wherein:

a. The fluorescence property comprises the intrinsic fluorescence of the portion of the skin;

b. The tissue state comprises the concentration of glycation end-products;

c. Using a multivariate method comprises applying a multivariate model relating intrinsic fluorescence of skin to the concentration of glycation end-products.

45. A method according to claim 43, wherein determining a fluorescence property comprises determining the tissue'"'"'s response to amplitude-modulated excitation light, a short pulse of excitation light, or polarized excitation light, or a combination thereof.

47. A method according to claim 43, wherein determining a fluorescence property comprises the using confocal detection or optical coherence tomography to discriminate the tissue depth from which the fluorescence property originates.

48. A method according to claim 43, wherein determining a fluorescence property comprises using raster scanning or imaging optics to obtain information regarding the spatial distribution of the fluorescence property.

49. A method according to claim 43, wherein determining a fluorescence property comprises using an optical probe optimized to discriminate the tissue depth from which the fluorescence property originates.

50. A method according to claim 43, wherein determining a fluorescence property comprises using a fiber optic probe with source and receiver fibers arranged in a spatial pattern that discriminates the tissue depth from which the fluorescence property originates.