Applications of hyperspectral laser speckle imaging

• US 20160198961A1
• Filed: 01/14/2015
• Published: 07/14/2016
• Est. Priority Date: 01/14/2015
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Homyk, Andrew, Thompson, Jason Donald
• Granted Patent: US 9,931,040 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 5/0066 Optical coherence imaging
• 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 5/0082 adapted for particular medical purposes
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/72 Signal processing specially adapted for physiological signals or for diagnostic purposes character recognition, recognising digital ink, document-oriented image-based pattern recognition G06V30/00; recognition or understanding of postal images G06V30/424

Abstract

Systems and methods are provided for detecting the flow of blood or other fluids in biological tissue by illuminating the biological tissue with two or more beams of coherent light and detecting responsively emitted light. A difference in wavelength, coherence length, beam divergence, or some other property of the beams of illumination causes the beams to preferentially scatter from, be absorbed by, or otherwise interact with respective elements of the biological tissue. Flow properties in one or more regions of the biological tissue (e.g., a region with which both beams of light preferentially interact, a region with which only one of the beams preferentially interacts) could be determined based on detected responsively emitted light from the biological tissue. Variations in speckle patterns over time and/or space, Doppler shifts, or some other properties of the detected light could be used to determine the flow properties.

Claims

1. A system comprising:

a light source, wherein the light source is configured to (i) emit a first beam of coherent illumination into a biological tissue and (ii) emit a second beam of coherent illumination into the biological tissue, wherein the first and second beams differ with respect to at least one of wavelength, coherence length, or beam divergence;

a light sensor configured to receive light from the biological tissue emitted in response to illumination by the light source; and

a controller operably coupled to the light sensor and light source, wherein the controller comprises a computing device programmed to perform controller operations comprising;

emitting the first beam of coherent illumination into the biological tissue using the light source;

detecting, using the light sensor, a first property of light received from the biological tissue in response to illumination by the first beam of illumination;

emitting the second beam of coherent illumination into the biological tissue using the light source;

detecting, using the light sensor, a second property of light received from the biological tissue in response to illumination by the second beam of illumination; and

determining at least one flow property in the biological tissue based on the first and second properties of the received light detected using the light sensor.

2. The system of claim 1, wherein the light source comprises first and second lasers configured to emit the first and second beams of coherent illumination, respectively.

3. The system of claim 1, wherein the first and second beams of coherent illumination have respective different first and second wavelengths.

4. The system of claim 3, wherein the light source comprises a tunable laser configured to emit coherent illumination at at least the first and second wavelengths during respective at least two periods of time.

5. The system of claim 1, wherein the first and second beams of coherent illumination have respective first and second coherence lengths.

6. The system of claim 5, wherein the light source comprises a laser configured to emit coherent illumination at at least the first and second coherence lengths by detuning a cavity of the laser during respective at least two periods of time.

7. The system of claim 1, wherein the first and second beams of coherent illumination preferentially interact with respective first and second sets of elements of the biological tissue.

8. The system of claim 1, wherein the first and second beams of coherent illumination preferentially interact with elements of the biological tissue within respective first and second ranges of depths within the biological tissue.

9. The system of claim 1, wherein the first and second beams of illumination have respective specified wavelengths, wherein the specified wavelengths are between approximately 400 nanometers and approximately 1000 nanometers.

10. The system of claim 1, wherein the light source is configured to emit the first beam of coherent illumination such that the first beam of coherent illumination is polarized in a first direction, and further comprising a polarization filter, wherein the polarization filter is configured to substantially prevent light emitted from the biological tissue from being received by the light sensor.

11. A method comprising:

emitting a first beam of coherent illumination into a biological tissue;

detecting a first property of light received from the biological tissue in response to illumination by the first beam of illumination;

emitting a second beam of coherent illumination into the biological tissue, where the second beam differs from the first beam with respect to at least one of wavelength, coherence length, or beam divergence;

detecting a second property of light received from the biological tissue in response to illumination by the second beam of illumination; and

determining at least one flow property in the biological tissue based on the detected first and second properties of the received light.

12. The method of claim 11, wherein emitting the first beam of illumination comprises emitting light from a first laser of a light source and emitting the second beam of illumination comprises emitting light from a second laser of the light source.

13. The method of claim 12, wherein emitting the first beam of illumination comprises emitting light from the first laser during a first period of time and wherein emitting the second beam of illumination comprises emitting light from the second laser during a second period of time that is non-overlapping with the first period of time.

14. The method of claim 11, wherein the first beam of illumination and the second beam of illumination are emitted at the same time.

15. The method of claim 11, wherein the first and second beams of coherent illumination have respective different first and second wavelengths, respectively.

16. The method of claim 11, wherein the first and second beams of coherent illumination have respective different first and second coherence lengths, respectively.

17. The method of claim 11, wherein the first and second beams of coherent illumination preferentially interact with respective first and second sets of elements of the biological tissue, and wherein determining at least one flow property in the biological tissue based on the detected first and second properties of the received light comprises determining a flow property of one or more elements of the first set of elements in the biological tissue relative to one or more elements of the second set of elements in the biological tissue.

18. The method of claim 11, wherein the first and second beams of coherent illumination preferentially interact with elements of the biological tissue within respective first and second ranges of depths within the biological tissue, and wherein determining at least one flow property in the biological tissue based on the detected first and second properties of the received light comprises determining a flow property of one or more elements within the first range of depths within the biological tissue relative to one or more elements within the second range of depths within the biological tissue.

19. The method of claim 11, wherein detecting a first property of light received from the biological tissue in response to illumination by the first beam of illumination comprises detecting at least one time-varying pattern of constructive and destructive interference in light received from a corresponding at least one portion of the biological tissue, and wherein determining at least one flow property in the biological tissue based on the detected first and second properties of the received light comprises determining at least one flow property in the biological tissue based at least on the detected at least one time-varying pattern of constructive and destructive interference.

20. The method of claim 11, wherein the first beam of illumination has a specified wavelength, wherein detecting a first property of light received from the biological tissue in response to illumination by the first beam of illumination comprises detecting at least one difference in the wavelength of light received from a corresponding at least one portion of the biological tissue relative to the specified wavelength of the first beam of illumination, and wherein determining at least one flow property in the biological tissue based on the detected first and second properties of the received light comprises determining at least one flow property in the biological tissue based at least on the detected at least one difference in the wavelength of light received from a corresponding at least one portion of the biological tissue relative to the specified wavelength of the first beam of illumination.