Multi-Wavelength Spatial Domain Near Infrared Oximeter to Detect Cerebral Hypoxia-Ischemia

• US 20080139908A1
• Filed: 11/13/2007
• Published: 06/12/2008
• Est. Priority Date: 05/13/2005
• Status: Abandoned Application

• Current Assignee: Charles Dean Kurth
• Original Assignee: Charles Dean Kurth
• Inventors: Kurth, Charles Dean
• Application Number:
  US11/939,141
• Publication Number:
  US 20080139908A1
• Time in Patent Office: Days
• US Class Current: 600/340
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/4076 Diagnosing or monitoring particular conditions of the nervous system A61B5/4821, A61B5/4824 take precedence
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: G01N 2021/3144 for oxymetry
• CPC Class Codes: G01N 21/359 using near infrared light

Abstract

Methods and apparatus for measuring cerebral O₂ saturation and detecting cerebral hypoxia-ischemia using multi-wavelength near infrared spectroscopy (NIRS). Near-infrared light produced by an emitter is directed through brain tissue. The intensity of the light that passes through the brain tissue is measured using photodiode detectors positioned at distinct distances from the emitter. This process is conducted for at least three wavelengths of near-infrared light. One of the wavelengths used is substantially at an isobestic point for oxy-hemoglobin and deoxy-hemoglobin, but the other two may be any wavelengths within the near-infrared spectrum (700 nm to 900 nm), so long as one of the additional wavelengths is greater than the isobestic point and the other is less than the isobestic point. Tissue oxygenation is calculated using an algorithm derived from the Beer-Lambert law. Cerebral hypoxia-ischemia may be diagnosed using the calculated tissue oxygenation value.

Claims

1. A method for measuring brain oxygen saturation using multi-wavelength near infrared spectroscopy (NIRS), comprising the steps of:

sending light of a first near infrared wavelength through an amount of brain tissue, with the assistance of a near infrared light emitter;

measuring a first set of at least three intensities of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of at least three photodiode detectors positioned at least three distances from the near infrared light emitter;

sending light of a second near infrared wavelength through an amount of brain tissue, with the assistance of the near infrared light emitter;

measuring a second set of at least three intensities of the light of the second near infrared wavelength that passes through the brain tissue, with the assistance of the at least three photodiode detectors positioned at the at least three distances from the near infrared light emitter;

sending light of a third near infrared wavelength through an amount of brain tissue, with the assistance of the near infrared light emitter;

measuring a third set of at least three intensities of the light of the third near infrared wavelength that passes through the brain tissue, with the assistance of at least three photodiode detectors positioned at the at least three distances from the near infrared light emitter; and

calculating a saturation of tissue oxygenation using an algorithm derived from the Beer-Lambert law and based at least upon one or more ratios of measured intensities at two or more near infrared wavelengths and one or more ratios of measured intensities at two or more photodiode detectors.

2. The method of claim 1, wherein the first near infrared wavelength is substantially an isobestic point for oxy-hemoglobin and deoxy-hemoglobin, the second near infrared wavelength is shorter than the first wavelength, and the third near infrared wavelength is longer than the first wavelength.

3. The method of claim 2, further comprising the step of:

comparing the calculated saturation of tissue oxygenation to one or more sets of medical diagnosis standards to determine an existence of cerebral hypoxia-ischemia or a lack of cerebral hypoxia-ischemia.

4. The method of claim 2, wherein the at least three distances include a first distance, a second distance that is incrementally longer than the first distance and a third distance that is incrementally longer than the third distance.

5. The method of claim 4, wherein the calculating step includes calculating the saturation of tissue oxygenation, S_O2, from substantially the following equation,

6. A method for measuring brain oxygen saturation using multi-wavelength near infrared spectroscopy (NIRS), comprising the steps of:

(a) sending light of a first near infrared wavelength through an amount of brain tissue, with the assistance of a near infrared light emitter;

(b) measuring a first intensity of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of a first photodiode detector positioned a first distance from the near infrared light emitter;

(c) measuring a second intensity of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of a second photodiode detector positioned a second distance from the near infrared light emitter;

(d) measuring a third intensity of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of a third photodiode detector positioned a third distance from the near infrared light emitter;

(e) repeating steps (a) through (d) a plurality of times for light of a corresponding plurality of near infrared wavelengths; and

(f) calculating a saturation of tissue oxygenation using an algorithm derived from the Beer-Lambert law and based at least upon one or more ratio of measured intensities at two or more of the near infrared wavelengths and one or more ratios of measured intensities at the two or more photodiode detectors.

7. The method of claim 6, wherein the first near infrared wavelength is substantially an isobestic point for oxyhemoglobin and deoxyhemoglobin, at least one of the near infrared wavelengths is shorter than the first near infrared wavelength, and at least one of the near infrared wavelengths is longer than the first near infrared wavelength.

8. The method of claim 7, further comprising the step of:

comparing the calculated saturation of tissue oxygenation to one or more sets of medical diagnosis standards to determine an existence of cerebral hypoxia-ischemia or a lack of cerebral hypoxia-ischemia.

9. A method for measuring brain oxygen saturation using multi-wavelength near infrared spectroscopy (NIRS), comprising the steps of:

(a) sending light of a first near infrared wavelength through an amount of brain tissue, with the assistance of a near infrared light emitter;

(b) measuring a first set of a plurality of intensities of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of a plurality of photodiode detectors positioned at corresponding plurality distances from the near infrared light emitter;

(c) repeating the steps (a) and (b) for light of a plurality of near infrared wavelengths; and

(d) calculating a saturation of tissue oxygenation using an algorithm derived from the Beer-Lambert law and based at least upon one or more ratios of measured intensities at two or more of the near infrared wavelengths and one or more ratios of measured intensities at two or more of the photodiode detectors.

10. The method of claim 9, wherein the first near infrared wavelength is substantially an isobestic point for oxyhemoglobin and deoxyhemoglobin, at least one of the near infrared wavelengths is shorter than the first near infrared wavelength, and at least one of the near infrared wavelengths is longer than the first near infrared wavelength.

11. The method of claim 10, further comprising the step of:

comparing the calculated saturation of tissue oxygenation to one or more sets of medical diagnosis standards to determine an existence of cerebral hypoxia-ischemia or a lack of cerebral hypoxia-ischemia.

12. The method of claim 10, wherein the calculating step includes calculating the saturation of tissue oxygenation, S_O2, from substantially the following equation,

13. A method for measuring brain oxygen saturation using multi-wavelength near infrared spectroscopy (NIRS), comprising the steps of:

sending light of a first near infrared wavelength through an amount of brain tissue, with the assistance of a near infrared light emitter;

measuring a first intensity of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of a first photodiode detector positioned a first distance from the near infrared light emitter;

measuring a second intensity of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of a second photodiode detector positioned a second distance from the near infrared light emitter;

measuring a third intensity of the light of the first near infrared wavelength that passes through the brain tissue, with the assistance of a third photodiode detector positioned a third distance from the near infrared light emitter;

sending a light of a second near infrared wavelength through the amount of brain tissue, with the assistance of the near infrared light emitter;

measuring a fourth intensity of light of the second near infrared wavelength that passes through the brain tissue, with the assistance of the first photodiode detector positioned the first distance from the near infrared light emitter;

measuring a fifth intensity of light of the second near infrared wavelength that passes through the brain tissue, with the assistance of the second photodiode detector positioned the second distance from the near infrared light emitter;

measuring a sixth intensity of light of the second near infrared wavelength that passes through the brain tissue, with the assistance of the third photodiode detector positioned the third distance from the near infrared light emitter;

sending a light of a third near infrared wavelength through the amount of brain tissue, with the assistance of the near infrared light emitter;

measuring a seventh intensity of light of the third near infrared wavelength that passes through the brain tissue, with the assistance of the first photodiode detector positioned the first distance from the near infrared light emitter;

measuring an eighth intensity of light of the third near infrared wavelength that passes through the brain tissue, with the assistance of the second photodiode detector positioned the second distance from the near infrared light emitter;

measuring a ninth intensity of light of the third near infrared wavelength that passes through the brain tissue, with the assistance of the third photodiode detector positioned the third distance from the near infrared light emitter; and

calculating a saturation of tissue oxygenation using an algorithm derived from the Beer-Lambert law and based at least upon one or more ratios of measured intensities at two or more of the near infrared wavelengths and one or more ratios of measured intensities at two or more of the photodiode detectors.

14. The method of claim 13, wherein the first near infrared wavelength is substantially an isobestic point for oxy-hemoglobin and deoxy-hemoglobin, the second near infrared wavelength is shorter than the first wavelength, and the third near infrared wavelength is longer than the first wavelength.

15. The method of claim 14, further comprising the step of:

comparing the calculated saturation of tissue oxygenation to one or more sets of medical diagnosis standards to determine an existence of cerebral hypoxia-ischemia or a lack of cerebral hypoxia-ischemia.

16. The method of claim 13, wherein the first near infrared wavelength is 805 nm, the second near infrared wavelength is 730 nm, the third near infrared wavelength is 850 nm, the first distance is 2 cm, the second distance is 3 cm and the third distance is 4 cm.

17. The method of claim 16, further comprising the step of:

comparing the calculated saturation of tissue oxygenation to one or more sets of medical diagnosis standards to determine an existence of cerebral hypoxia-ischemia or a lack of cerebral hypoxia-ischemia.

18. The method of claim 14, wherein the calculating step includes calculating the saturation of tissue oxygenation, S_O2, from substantially the following equation,

19. An apparatus for measuring brain oxygen saturation comprising:

a probe housing;

a near-infrared light emitter housed within the probe housing;

a first photodiode detector positioned a first distance from the emitter;

a second photodiode detector positioned at a second distance from the emitter, the second distance being longer than the first distance; and

a third photodiode detector positioned at a third distance from the emitter, the third distance being longer than the second distance.

20. The apparatus of claim 19, wherein the probe housing includes an apparatus for securing the housing to the head of a patient.