METHOD AND APPARATUS FOR CEREBRAL OXIMETRY

• US 20110066014A1
• Filed: 09/03/2010
• Published: 03/17/2011
• Est. Priority Date: 05/03/2006
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Wilfley, Brian Patrick, Funk, Tobias, Bechtel, Kate Leeann, Heanue, Joseph Anthony
• Granted Patent: US 8,433,384 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• 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 5/0091 for mammography
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/415 the glands, e.g. tonsils, adenoids or thymus
• CPC Class Codes: A61B 5/418 lymph vessels, ducts or nodes
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0205 Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/4406 Fluorescence spectrometry
• CPC Class Codes: G01N 21/6408 with measurement of decay time, time resolved fluorescence
• CPC Class Codes: G01N 2201/0826 Fibre array at source, distributing
• CPC Class Codes: G01N 2201/0833 Fibre array at detector, resolving

Abstract

The present invention pertains to a method and apparatus for cerebral oximetry. A modulated optical signal based on a digital code sequence is transmitted to the human brain. A temporal transfer characteristic is derived from the modulated optical signal. Oxygen level in the brain is determined based on the temporal transfer characteristic.

Claims

1. A cerebral oximetry measurement system for measuring oxygen level in a human brain comprising:

a signal generator for generating a digital modulation signal representing a code sequence;

an optical illumination source coupled to said signal generator for receiving said digital modulation signal and for transmitting a modulated optical signal along an optical transmission path to said human brain in response to said digital modulation signal;

a detector optically coupled to said human brain for receiving said modulated optical signal after transmission through optical transmission path through said human brain; and

a processor coupled to said detector for deriving a temporal transfer characteristic for said optical signal received by said detector and for determining said oxygen level based on said temporal transfer characteristic.

2. The cerebral oximetry measurement system of claim 1 further comprising:

a delay component optically coupled to said optical illumination source for increasing length of said optical transmission path.

3. The cerebral oximetry measurement system of claim 2 wherein said delay component further comprises a reflective surface.

4. The cerebral oximetry measurement system of claim 1 wherein said code sequence further comprises multiple identical code sequences of a single code sequence.

5. The cerebral oximetry measurement system of claim 1 wherein said code sequence is circular.

6. The cerebral oximetry measurement system of claim 1 wherein said code sequence is orthogonal.

7. The cerebral oximetry measurement system of claim 1 wherein said code sequence is unipolar.

8. The cerebral oximetry measurement system of claim 1 wherein said code sequence is a Galois code.

9. The cerebral oximetry measurement system of claim 1 wherein said code sequence is a maximal-length sequence.

10. The cerebral oximetry measurement system of claim 1 further comprising:

a second signal generator for generating a second digital modulation signal representing a second code sequence;

a second optical illumination source coupled to said second signal generator for receiving said second digital modulation signal and for transmitting a second modulated optical signal to said human brain in response to said second digital modulation signal.

11. The cerebral oximetry measurement system of claim 10 wherein said second code sequence and said code sequence have the same ordering of code elements and begin at different code elements.

12. A method for measuring oxygen level in a human brain comprising:

generating a digital modulation signal associated with a code sequence;

generating a modulated optical signal based on said digital modulation signal;

transmitting said modulated optical signal to said human brain;

receiving a modified version of said modulated optical signal after transmission through said human brain;

deriving a temporal transfer characteristic for said modified version of said modulated optical signal; and

calculating said oxygen level based on said temporal transfer characteristic.

13. The method of claim 12 further comprising:

delaying said modulated optical signal to reduce noise effects.

14. The method of claim 12 further comprising:

determining an absorption coefficient of said human brain from said temporal transfer characteristic.

15. The method of claim 12 wherein said code sequence is circular.

16. The method of claim 12 wherein said code sequence is unipolar.

17. The method of claim 12 wherein said code sequence is orthogonal.

18. The method of claim 12 further comprising:

generating a second digital modulation signal associated with a second code sequence;

generating a second modulated optical signal based on said second digital modulation signal;

transmitting said second modulated optical signal to said human brain;

receiving a second modified version of said second modulated optical signal after transmission through said human brain; and

deriving a second temporal transfer characteristic for said second modified version of said second modulated optical signal.

19. The method of claim 12 further comprising:

delaying said code sequence to generate a second code sequence;

generating a second digital modulation signal associated with said second code sequence;

generating a second modulated optical signal based on said second digital modulation signal;

transmitting said second modulated optical signal to said human brain;

receiving a second modified version of said second modulated optical signal after transmission through said human brain; and

deriving a second temporal transfer characteristic for said second modified version of said second modulated optical signal.

20. A cerebral oximetry measurement system for measuring oxygen level in a human brain comprising:

means for generating a digital modulation signal associated with a code sequence;

means for generating a modulated optical signal based on said digital modulation signal;

means for transmitting said modulated optical signal to said human brain;

means for receiving a modified version of said modulated optical signal after transmission through said human brain;

means for deriving a temporal transfer characteristic for said modified version of said modulated optical signal; and

means for calculating said oxygen level based on said temporal transfer characteristic.