SPECTROSCOPIC SENSORS

• US 20110205535A1
• Filed: 08/07/2009
• Published: 08/25/2011
• Est. Priority Date: 08/07/2008
• Status: Active Grant

• Current Assignee: University Of Massachusetts
• Original Assignee: University Of Massachusetts
• Inventors: Coates, John, Yang, Ye, Jin, Chunguang, Soller, Babs R.
• Granted Patent: US 9,095,291 B2
• Time in Patent Office: Days
• US Class Current: 356/300
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2562/0238 Optical sensor arrangements for performing transmission measurements on body tissue
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• CPC Class Codes: A61B 2562/04 Arrangements of multiple sensors of the same type
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/0082 adapted for particular medical purposes
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface

Abstract

Disclosed herein are sensors that include: (a) a circuit board that includes an electronic processor; (b) a plurality of radiation sources, each source being attached to the circuit board; and (c) a spectral detector attached to the circuit board, the spectral detector being configured to analyze radiation derived from one or more of the plurality of radiation sources. During use, the sensors are configured to be worn on a portion of a body of a subject. The electronic processor is configured to cause two or more of the plurality of radiation sources to direct incident radiation to the subject, to cause the spectral detector to analyze radiation from the subject, and to determine one or more properties of the subject based on the radiation from the subject. Methods of making and using these sensors are also disclosed.

Claims

1. A sensor, comprising:

a circuit board comprising an electronic processor;

a plurality of radiation sources, each source being attached to the circuit board; and

a spectral detector attached to the circuit board, the spectral detector being configured to analyze radiation derived from one or more of the plurality of radiation sources,

wherein during use the sensor is configured to be worn on a portion of a body of a subject; and

wherein the electronic processor is configured to cause two or more of the plurality of radiation sources to direct incident radiation to the subject, to cause the spectral detector to analyze radiation from the subject, and to determine one or more properties of the subject based on the radiation from the subject.

2. The sensor of claim 1, wherein the electronic processor is configured to selectively adjust at least one of the radiation sources to produce the incident radiation.

3. The sensor of claim 2, wherein the electronic processor is configured to selectively adjust at least one of (i) a duty cycle of, and (ii) an electrical drive current supplied to, each of the radiation sources to produce incident radiation having a selected spectral shape.

4. The sensor of claim 1, wherein the radiation sources comprise a short-distance source positioned at a distance of 9 mm or less from the detector, and at least two long-distance sources each positioned at a distance of 10 mm or more from the detector.

5. The sensor of claim 1, wherein the radiation sources comprise at least two short-distance sources and at least three long-distance sources.

6. The sensor of claim 4, wherein the electronic processor is configured to:

select one of the long-distance sources to produce at least a portion of the incident radiation by illuminating the subject with incident radiation produced by each of the long-distance sources;

measure an absorbance spectrum of the subject corresponding to illumination by each of the long-distance sources; and

compare the measured absorbance spectra to select one of the long-distance sources.

7. The sensor of claim 6, wherein the comparing comprises:

for each of the long-distance sources, fitting the absorbance spectrum corresponding to the long-distance source to a Taylor series model for the subject'"'"'s absorbance spectrum, and determining an average error between the absorbance spectrum and the model; and

selecting the long-distance source corresponding to a smallest average error between the absorbance spectrum and the model.

8. The sensor of claim 7, wherein the comparing further comprises, prior to fitting the absorbance spectra corresponding to the long-distance sources, correcting each of the absorbance spectra corresponding to the long-distance sources to reduce spectral effects due to layers of skin and fat in the subject using information derived from an absorbance spectrum obtained by exposing the subject to radiation from the short-distance source.

9. The sensor of claim 7, wherein selecting the long-distance source further comprises determining whether the selected long-distance source satisfies a minimum suitability criterion.

10. The sensor of claim 9, wherein determining whether the selected long-distance source satisfies a minimum suitability criterion comprises determining an average value (μ

) and a standard deviation (σ

) of model fitting errors, and wherein the electronic processor is configured to select the long-distance source if an average error between the model and an absorbance spectrum corresponding to the selected long-distance source is within an interval (μ

−

3σ

, μ

+3σ

).

11. The sensor of claim 10, wherein:

the radiation sources comprise two or more short-distance sources; and

wherein the electronic processor is configured to select a combination of a short-distance source and a long-distance source to produce at least a portion of the incident radiation by;

illuminating the subject with incident radiation produced by each of the short-distance sources;

measuring absorbance spectra corresponding to each of the short-distance sources;

correcting each of the spectra corresponding to the long-distance sources with each of the spectra corresponding to the short-distance sources;

fitting the corrected spectra to a Taylor series model for the subject'"'"'s absorbance spectrum and determining a fitting error between each of the corrected spectra and the model; and

identifying a combination comprising a short-distance source and a long-distance source that corresponds to a smallest fitting error among the corrected spectra.

12. The sensor of claim 1, further comprising a display unit, wherein the display unit is positioned on a surface of the sensor opposite to a surface through which the incident radiation is emitted by the plurality of radiation sources, and wherein the display unit is configured to display values of at least some of the one or more properties of the subject and previously measured values of the one or more properties of the subject.

13. The sensor of claim 1, further comprising a communication interface comprising a wireless transmitter and receiver configured to transmit data to and from the sensor, wherein the sensor is configured to transmit the data over a network.

14. The sensor of claim 1, wherein the one or more properties comprise at least one of oxygen saturation, oxygen tension, pH, hematocrit, hemoglobin concentration, anaerobic threshold, water content, and oxygen consumption of the subject.

15. The sensor of claim 1, wherein the electronic processor is configured to maintain a non-zero measured detector signal intensity within a predetermined range of signal intensities during analysis of the radiation from the subject.

16. The sensor of claim 15, wherein maintaining the detector signal intensity within a predetermined range comprises adjusting at least one of an electronic gain of the detector and a signal acquisition time to control the signal intensity.

17. The sensor of claim 15, wherein maintaining the detector signal intensity within a predetermined range comprises selecting a different one of the plurality of radiation sources to direct incident radiation to the subject.

18. The sensor of claim 17, wherein selecting a different one of the plurality of radiation sources comprises selecting a different radiation source from among the radiation sources positioned at a distance of 10 mm or more from the detector.

19. The sensor of claim 17, wherein selecting a different one of the plurality of radiation sources comprises selecting a different radiation source from among the radiation sources positioned at a distance of 9 mm or less from the detector.

20. The sensor of claim 1, wherein the electronic processor is configured to provide information about the one or more properties of the subject to a therapeutic device to control the therapeutic device.

21. A sensor, comprising:

a flexible mounting member comprising an adhesive surface configured to attach directly to a sample and to assume a shape corresponding to at least a portion of the sample when it attaches to the sample; and

a plurality of radiation sources, a spectral detector, and an electronic processor attached to the mounting member,

wherein the electronic processor is configured to cause at least two of the radiation sources to direct incident radiation to a sample, to cause the spectral detector to analyze radiation from the sample, and to determine one or more properties of the sample based on the radiation from the sample.

22. The sensor of claim 21, wherein the mounting member comprises a first disposable portion that contacts the sample, and a second non-disposable portion to which the plurality of radiation sources, the detector, and the electronic processor are attached, wherein the disposable portion is at least partially transmissive to near-infrared radiation and forms a window through which incident radiation produced by the radiation sources passes to reach the sample.

23. The sensor of claim 21, wherein the one or more properties comprise at least one of oxygen tension, oxygen saturation, pH, hematocrit, hemoglobin concentration, anaerobic threshold, water content, and oxygen consumption of the sample.

24. A method for measuring one or more sample properties, the method comprising:

selecting one of a plurality of radiation sources and directing radiation from the selected source to be incident on the sample, detecting radiation from the sample, and determining the one or more sample properties based on the detected radiation,

wherein the selecting comprises;

for each one of the plurality of radiation sources, measuring an absorbance spectrum of the sample by exposing the sample to radiation from the radiation source;

fitting the absorbance spectra to a model for absorbance of the sample, and determining an average fitting error for each spectrum relative to the model; and

selecting the source that corresponds to the spectrum with the smallest average fit error.

25. The method of claim 24, wherein the selecting further comprises correcting each of the absorbance spectra to reduce spectral effects due to skin and fat layers in the sample prior to determining the average fitting errors.

26. The method of claim 24, wherein the selecting further comprises determining an average value μ

and a standard deviation value σ

related to the fitting errors, and selecting a source for which the average fitting error determined from the absorbance spectrum corresponding to the source is within an interval (μ

−

3σ

, μ

+3σ

).

27. The method of claim 24, further comprising, during the detection of radiation from the sample, maintaining an intensity of a detected radiation signal greater than zero and within a predetermined range of signal intensities.

28. The method of claim 27, wherein maintaining the signal intensity within a predetermined range comprises adjusting at least one of an electronic gain of the detector and a signal acquisition time during which the radiation is detected to control the signal intensity.

29. The method of claim 27, wherein maintaining the signal intensity within a predetermined range comprises selecting a different one of the plurality of radiation sources to direct radiation to the sample.

30. The method of claim 24, wherein the one or more sample properties comprise at least one of oxygen saturation, oxygen tension, pH, hematocrit, hemoglobin concentration, anaerobic threshold, water content, and oxygen consumption of the sample.