Diffuse reflectance spectroscopy

• US 20040092822A1
• Filed: 11/12/2002
• Published: 05/13/2004
• Est. Priority Date: 11/12/2002
• Status: Active Grant

• Current Assignee: Inlight Solutions, Inc.
• Original Assignee: Inlight Solutions, Inc.
• Inventors: Messerschmidt, Robert G., Robinson, M. Ries
• Granted Patent: US 7,623,906 B2
• Time in Patent Office: Days
• US Class Current: 600/473
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• 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 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters

Abstract

An improved method and apparatus for diffuse reflectance spectroscopy. A specular control device is provided that can discriminate between diffusely reflected light that is reflected from selected depths or layers within the tissue. The specular control device permits a spectroscopic analyzer to receive the diffusely reflected light that is reflected from, for example, a first layer or depth within the tissue, while preventing the remaining diffusely reflected light from reaching the spectroscopic analyzer. Furthermore, the specular control device may prevent the specularly reflected light (e.g. surface reflected light) from reaching the spectroscopic analyzer.

Claims

1. An apparatus for obtaining a diffuse reflectance spectrum from tissue, comprising:

a. generating means for generating infrared energy;

b. directing means for directing said infrared energy to said tissue;

c. collecting means for collecting infrared energy that is reflected by said tissue;

d. discrimination means for discriminating between infrared energy that is diffusely reflected from a first depth within said tissue from infrared energy that is diffusely reflected from a second depth within said tissue, said discrimination means specifically sized for substantially preventing said infrared energy that is diffusely reflected from the first depth from reaching said collecting means.

2. The apparatus of claim 1 wherein said discrimination means comprises a blocker blade adapted to be positioned on or adjacent to a surface of said tissue.

3. The apparatus of claim 2 wherein said blocker blade is adapted to extend substantially perpendicular to the surface of said tissue, and has two opposing surfaces including a front surface and a back surface defining a thickness thereof.

4. The apparatus of claim 3 wherein said directing means directs said infrared energy to form an illuminated portion of the surface of said tissue.

5. The apparatus of claim 4 wherein the back surface of said blocker blade is laterally spaced a predetermined distance from said illuminated portion of said tissue such that infrared energy that is diffusely reflected from the first depth within said tissue is substantially prevented from reaching said collecting means.

6. The apparatus of claim 5 wherein the front surface of said blocker blade is adjacent to said illuminated portion of said tissue.

7. The apparatus of claim 3 wherein said blocker blade thickness defined by said front surface and said back surface is sufficient to prevent infrared energy that is diffusely reflected from the first depth from reaching said collecting means.

8. The apparatus of claim 3 wherein said blocker blade absorbs diffusely reflected infrared energy incident thereon.

9. The apparatus of claim 1, wherein the first depth corresponds to an epidermis layer of said tissue, and wherein the second depth corresponds to a dermis layer of said tissue.

13. The apparatus of claim 1, wherein said discrimination means comprises a blocker blade having a thickness great enough to prevent light from leaking under the discrimination means due to the roughness of said tissue top surface.

10. An apparatus for obtaining a diffuse reflectance spectrum from human tissue, comprising:

a. generating means for generating infrared energy;

b. directing means for directing said infrared energy to said tissue;

c. collecting means for collecting infrared energy that is reflected by said tissue; and

d. discrimination means for discriminating between infrared energy that is diffusely reflected from a first selected depth within said tissue from infrared energy that is diffusely reflected from a second selected depth, said discrimination means specifically sized for substantially preventing said infrared energy that is diffusely reflected from said first selected depth from reaching said collecting means; and

e. said discrimination means comprises a blocker blade adapted to be positioned on or adjacent to the surface of said tissue, said directing means including an immersion lens, with said blocker blade positioned within said immersion lens.

11. A method for obtaining a diffuse reflectance spectrum from human skin tissue for the noninvasive determination of a biological attribute thereof, the human skin tissue having an epidermis layer and a dermis layer, the method comprising the steps of:

a. generating infrared energy;

b. directing said infrared energy to said tissue;

c. collecting the infrared energy that is reflected from the dermis layer while discouraging the collection of infrared energy that is reflected from the epidermis layer with a discriminating means; and

d. determining the biological attribute by analyzing the collected infrared energy.

12. The method of claim 11 wherein the directing step directs said infrared energy to a top surface of said tissue.

14. The method of claim 11, wherein directing the infrared energy to a said tissue comprises directing infrared energy to a first location on said tissue, and wherein collecting the infrared energy comprises collecting the infrared energy at a second location on said tissue, wherein only infrared energy that is reflected from the dermis layer is present at the second location.

37. A method as in claim 11, wherein the biological attribute is an analyte concentration, a disease state, or a tissue characteristic.

40. A method as in claim 11, wherein the biological attribute is an indication of diabetes or impaired glucose tolerance.

15. An apparatus for obtaining a diffuse reflectance spectrum from skin tissue, the skin tissue having an epidermis layer and a dermis layer, the apparatus comprising:

a. a source of infrared energy for generating and delivering infrared energy to a first location on the skin tissue;

b. a collector for collecting infrared energy reflected from the dermis layer at a second location;

c. means for causing the collector to collect primarily only the infrared light that is reflected from the dermis layer.

16. An apparatus as in claim 15, wherein the means for causing the collector to collect primarily only the infrared energy that is reflected from the dermis layer is positioned between the infrared energy source and the collector.

17. An apparatus as in claim 16, wherein the means for causing the collector to collect primarily only the infrared energy that is reflected from the dermis layer comprises a blocker.

18. An apparatus as in claim 17, wherein the blocker comprises a plate.

19. An apparatus as in claim 18, wherein the plate comprises a material opaque to infrared energy.

20. An apparatus as in claim 18, wherein the plate includes a front surface and a back surface, and wherein the back surface is laterally spaced from an illumination location to block infrared energy that is reflected from the epidermis layer.

21. An apparatus as in claim 20, wherein the front surface is positioned adjacent the illumination location.

22. An apparatus as in claim 20, wherein the front surface is laterally spaced from the illumination location.

23. An apparatus as in claim 20, wherein the plate is solid between the front surface and the back surface.

24. An apparatus as in claim 20, wherein the plate is not solid between the front surface and the back surface.

25. An apparatus as in claim 18, wherein the plate has a thickness, the infrared energy has a wavelength, and the thickness is greater than the wavelength.

26. An apparatus as in claim 25, wherein the thickness is greater than or equal to 100 micrometers.

27. An apparatus as in claim 25, wherein the thickness is 100 micrometers to 800 micrometers.

28. A device for performing non-invasive determination of a biological attribute of tissue of a subject, the device comprising:

a. an input element for emitting infrared radiation on the tissue of the subject;

b. an output element for detecting at least a portion of the radiation not absorbed by the tissue of the subject, wherein on a ray basis the radiation emitted by the input element enters the tissue at an entrance point and the radiation detected by the output element exits the skin at an exit point, and wherein the entrance point and the exit point for individual rays are separated by a distance in the range of 100 μ

m to 800 μ

m to preferentially collect radiation primarily reflected from deeper within the tissue by the output element; and

c. a spectroscopic analyzer for analyzing the non-absorbed radiation and determining the biological attribute.

38. A device as in claim 28, wherein the biological attribute is an analyte concentration, a disease state, or a tissue characteristic.

41. A device as in claim 28, wherein the biological attribute is an indication of diabetes or impaired glucose tolerance.

29. A device for performing non-invasive determination of a biological attribute of tissue of a subject, the subject having tissue with an epidermis layer and a dermis layer, the device comprising:

a. an input element for emitting infrared radiation to the tissue of the subject;

b. an output element for detecting at least a portion of the radiation response of the tissue of the subject, wherein the radiation emitted by the input element enters the tissue at an entrance point and the radiation response comprises radiation detected by the output element that exits the tissue at an exit point, and wherein the entrance point and the exit point are separated by a distance; and

c. a spectroscopic analyzer for analyzing the radiation response and determining the biological attribute.

30. A device as in claim 29, wherein the distance is greater than 100 μ

m.

31. A device as in claim 29, wherein the distance is selected such that a majority of the radiation reflected by the epidermis layer is not detected by the output element.

32. A device as in claim 29, wherein the radiation response comprises radiation reflected by the tissue of the subject.

33. A device as in claim 29, wherein the radiation response comprises radiation not absorbed by the tissue of the subject.

34. A device as in claim 29, wherein the distance is such that there is a preferential collection of radiation that has penetrated beyond the surface of the tissue.

35. A device as in claim 34, wherein the distance is selected such that a substantial portion of the radiation reflected by the dermis layer is detected by the output element.

36. A device as in claim 34, wherein the distance is not less than 100 μ

m.

39. A device as in claim 29, wherein the biological attribute is an analyte concentration, a disease state, or a tissue characteristic.

42. A device as in claim 29, wherein the biological attribute is an indication of diabetes or impaired glucose tolerance.