Flowometry in Optical Coherence Tomography for Analyte Level Estimation

• US 20090275812A1
• Filed: 03/04/2009
• Published: 11/05/2009
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: GlucoLight Corporation
• Inventors: Reichgott, Samuel, Kechter, George, Schurman, Matthew J., Shakespeare, Walter J., Wallace, Phillip William
• Granted Patent: US 8,571,617 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 2576/00 Medical imaging apparatus involving image processing or analysis A61B1/00009, A61B6/52 and A61B8/52 take precedence; image processing per se G06T; details of algorithms for analysing medical images G06T7/0012
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/0073 by tomography, i.e. reconstruction of 3D images from 2D projections A61B5/0066 takes precedence
• 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 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• 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 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/4875 Hydration status, fluid retention of the body
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

Optical coherence tomography (herein “OCT”) based analyte monitoring systems are disclosed. In one aspect, techniques are disclosed that can identify fluid flow in vivo (e.g., blood flow), which can act as a metric for gauging the extent of blood perfusion in tissue. For instance, if OCT is to be used to estimate the level of an analyte (e.g., glucose) in tissue, a measure of the extent of blood flow can potentially indicate the presence of an analyte correlating region, which would be suitable for analyte level estimation with OCT. Another aspect is related to systems and methods for scanning multiple regions. An optical beam is moved across the surface of the tissue in two distinct manners. The first can be a coarse scan, moving the beam to provide distinct scanning positions on the skin. The second can be a fine scan where the beam is applied for more detailed analysis.

Claims

19. A method for determining the presence of fluid flow in a tissue sample using optical coherence tomography, comprising:

scanning a region in the tissue sample using OCT to provide fringe-modulated intensity data measurements; and

using amplitude modulation in the fringe-modulated intensity data measurements to determine whether fluid flow is present in the region.

20-25. -25. (canceled)

26. A system for determining at least one blood characteristic in a tissue sample, comprising:

an optical coherency tomography (OCT) apparatus configured to obtain intensity data measurements from each of a plurality of regions in the tissue sample; and

a processor configured to analyze the intensity data measurements from the OCT apparatus to determine whether blood flow is present in at least one region.

1. A method of determining blood analyte levels in a tissue sample using optical coherence tomography (OCT), comprising:

scanning a plurality of regions in the tissue sample using OCT to provide corresponding intensity data measurements;

analyzing the intensity data measurements to determine whether blood flow is present in the corresponding region; and

obtaining blood analyte levels from at least one of the regions having blood flow present as analyzed from OCT measurements.

2. The method of claim 1 wherein the intensity data measurements comprise signals from backscattered light to determine whether blood flow is present in the corresponding region.

3. The method of claim 1, wherein the intensity data measurements exhibit speckle, and the step of analyzing intensity data measurements comprises analyzing speckle in the intensity data measurements to determine whether blood flow is present.

4. The method of claim 1, wherein the intensity data measurements exhibit speckle, and the step of analyzing comprises comparing different intensity data measurements to determine whether blood flow is present.

5. The method of claim 4, wherein the step of scanning comprises scanning the plurality of regions over a plurality of moments in time to provide the corresponding intensity data measurements, the intensity data measurements exhibiting speckle, and further wherein the step of comparing comprises comparing intensity data taken over the plurality of time moments to determine whether blood flow is present.

6. The method of claim 5, wherein the scanning of each region comprises a scan of a locality at a plurality of depths.

7. The method of claim 4, wherein the step of comparing comprises comparing the plurality of intensity data measurements taken over the plurality of regions to determine whether blood flow is present.

8. The method of claim 7, wherein the scanning of each region comprises performing a raster scan.

9. The method of claim 1, wherein the step of scanning comprises scanning each of the plurality of regions such that the corresponding intensity data measurement comprises fringe-modulated data, and the step of analyzing comprises using the fringe-modulated data to determine whether blood flow is present in the corresponding region.

10. The method of claim 9, wherein the step of scanning comprises scanning the tissue sample in depth to provide intensity data measurements of regions having varying depths.

11. The method of claim 9, wherein the step of analyzing comprises determining a peak fringe-frequency shift in the intensity data to determine whether blood flow is present in the corresponding region.

12. The method of claim 9, wherein the step of analyzing comprises analyzing amplitude modulation in the fringe-modulated data to determine whether blood flow is present in the corresponding region.

13. The method of claim 12, wherein the step of analyzing comprises using digital signal processing to determine whether blood flow is present in the corresponding region.

14. The method of claim 12, wherein the step of analyzing comprises using analog signal processing to determine whether blood flow is present in the corresponding region.

15. The method of claim 12, wherein the intensity data measurements exhibit speckle, and the step of analyzing amplitude modulation in the fringe-modulated data comprises analyzing selected high frequency components of the intensity data to determine whether blood flow is present in the corresponding region.

16. The method of claim 9, wherein the step of analyzing comprises:

passing the intensity data measurements having fringe-modulated data through a filter, wherein the filter is configured to produce a filtered signal indicating fringe frequency modulation indicative of blood flow'"'"'s presence.

17. The method of claim 9, wherein the step of analyzing comprises:

passing the intensity data measurements having fringe-modulated data through a narrow band filter, wherein the narrow band filter is configured to produce a reduced intensity signal output from an intensity data measurement exhibiting blood flow.

18. The method of claim 17, wherein the step of analyzing further comprises:

passing the intensity data measurements having fringe-modulated data through a wide band filter, wherein the wide band filter is configured to produce an attenuated output exhibiting at least one fringe-modulated feature from an intensity data measurement exhibiting blood flow; and

comparing the reduced intensity signal output and the attenuated output to determine whether blood flow is present.

27. The system of claim 26, wherein the processor is configured to convert the intensity data measurements into blood analyte levels from at least one of the regions determined to have a selected level of blood flow.

28. The system of claim 26, wherein the processor is configured to analyze speckle in the intensity data measurements.

29. The system of claim 26, wherein the processor is configured to compare speckle in different intensity data measurements to determine whether blood flow is present.

30. The system of claim 29, wherein the OCT apparatus is configured to provide the different intensity data measurements over a plurality of moments in time.

31. The system of claim 29, wherein the OCT apparatus comprises a beam scanner.

32. The system of claim 31, wherein the beam scanner is configured to provide the different intensity measurements over at least one of a plurality of regions and a plurality of depths.

33. The system of claim 31, wherein the beam scanner is configured to provide raster scans of a plurality of regions.

34. The system of claim 33, wherein the processor is configured to analyze amplitude modulation in the fringe-modulated data.

35. The system of claim 34, wherein the processor is configured to analyze selected high frequency components of the intensity data.

36. The system of claim 33, wherein the processor comprises a signal filter for converting at least a portion of the intensity data measurements into a reduced intensity signal indicating fringe frequency modulation correlating with blood flow presence.

37. The system of claim 36, wherein the signal filter comprises a narrow band filter.

38. The system of claim 37, wherein the processor further comprises a wide band filter configured to convert at least a portion of the intensity data measurements into an attenuated output, the processor configured to compare the reduced intensity signal and the attenuated output to determine whether blood flow is present.

33-1. The system of claim 26, wherein the processor is configured to analyze fringe-modulated data in the intensity data measurements.