Method and apparatus for monitoring fetal cerebral oxygenation during childbirth

• US 6,381,480 B1
• Filed: 05/26/2000
• Issued: 04/30/2002
• Est. Priority Date: 11/26/1997
• Status: Expired due to Term

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Hugh Adam Stoddart, Hugh Franklin Stoddart, Thomas C. Sefranek
• Inventors: Stoddart, Hugh Franklin, Stoddart, Hugh Adam, Sefranek, Thomas C.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US09/555,351
• Time in Patent Office: 704 Days
• Field of Search: 600/300, 600/310, 600/313, 600/323, 600/326, 600/327, 600/338, 600/341, 600/342, 600/473, 356/39, 356/300, 356/317, 356/337, 422/82.05, 422/82.09, 436/63, 436/164, 436/171
• US Class Current: 600/338
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/1464 specially adapted for foetal tissue
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

An apparatus is disclosed for monitoring fetal cerebral oxygenation during childbirth. The apparatus includes a tunable source of infrared photons, a probe to access a single location on the scalp of the fetus for injecting the infrared photons generated by the photon source, and for receiving scattered photons reflected from within the skull of the fetus. The apparatus at least has first and second detectors for detecting the presence of photons received through the probe at selected different delay intervals so as to be capable of distinguishing photons reflected from different depths or at different instances from within the head of the fetus.

Claims

1. An apparatus for monitoring fetal cerebral oxygenation during childbirth comprising:

a source of infrared photons;

a probe to optically access a single location on the scalp of a fetus by injecting the infrared photons generated by said photon source at said location, and for receiving scattered photons reflected from within the skull of the fetus at said location; and

at least first and second detectors for detecting the presence of photons received by said probe at at least two different delay intervals so as to provide for distinguishing photons reflected at different instants or from different depths within the head of the fetus on the basis of said different delay intervals.

2. The apparatus as defined in claim 1, wherein said probe includes a photon injection site and a photon reception site that are within about 5 mm or less of each other.

3. The apparatus as defined in claim 1, wherein said photon source is a laser.

4. The apparatus as defined in claim 1, wherein said photon source emits a pulse of photons that are subsequently injected into the head of the fetus.

5. The apparatus as defined in claim 4, wherein the pulse of photons emitted from said photon source is less than about 1 ns in duration.

6. The apparatus as defined in claim 1, wherein said photon source emits near-infrared photons.

7. The apparatus as defined in claim 1, and further including a first fiberoptic cable optically coupling said photon source to said probe, and a second fiberoptic cable optically coupling said probe to said first and second detector.

8. The apparatus as defined in claim 1, wherein said first and second detectors are shuttered detectors, said first and second shuttered detectors each having a trigger input and detecting photons only during an interval when a trigger signal is applied to its trigger input.

9. The apparatus as defined in claim 8, wherein said photon source emits a pulse of photons that are subsequently injected into the head of the fetus, and wherein said apparatus further includes a beam splitter positioned between said photon source and said probe for transmitting a pulse of photons as a trigger signal to the trigger inputs of said first and second shuttered detectors at the same time the pulse of photons is transmitted to said probe.

10. The apparatus as defined in claim 9, and further including a first fiberoptic cable for transmitting the pulse of photons from said beam splitter to the trigger input of said first shuttered detector, and a second fiberoptic cable for transmitting the pulse of photons from said beam splitter to the trigger input of said second shuttered detector, said first and second fiberoptic cables having different lengths so as to trigger said first and second shuttered detectors at different delay times.

11. The apparatus as defined in claim 8, wherein said first and second shuttered detectors are configured to gate on and off in about 1 ns or less.

12. The apparatus as defined in claim 8, wherein said first and second shuttered detectors include image intensifiers.

13. The apparatus as defined in claim 12, wherein photons received from said probe are focussed onto a peripheral region of a photocathode of said image intensifiers.

14. The apparatus as defined in claim 1, and further including a fluorescence filter positioned between said probe and at least one of said first and second detectors.

15. The apparatus as defined in claim 1, and further including a photodetector and a beam splitter positioned between said probe and said first and second detectors so as to transmit a portion of the photons received from said probe to said photodetector.

16. The apparatus as defined in claim 1, wherein said photon source generates sequential pulses of photons at at least two different wavelengths.

17. A method for monitoring cerebral oxygenation of a human subject comprising the steps of:

generating a pulse of near-infrared photons;

injecting at least a portion of the generated pulse of photons into the scalp of the subject;

receiving scattered photons reflected from within the skull of the subject; and

detecting the presence of received photons at at least two different delay intervals relative to the generation of the pulse of photons so as to provide for distinguishing photons reflected at different instances or from different depths from within the head of the subject.

18. The method as defined in claim 17, and further including the step of determining relative quantity of photons at said two different delay intervals.

19. The method as defined in claim 18, and further including the step of using relative values to determine absorption and/or said different depths.

20. An apparatus for spectrophotometric analysis of an object, said apparatus comprising:

a source for emitting a pulse of photons that is injected into the object;

a photon receiver for receiving photons reflected from within the object;

a first shuttered detector having a trigger input for detecting the presence of photons received through said photon receiver during a first interval determined by a gating pulse applied to said trigger input;

a second shuttered detector having a trigger input for detecting the presence of photons received through said photon receiver during a second interval determined by a gating pulse applied to said trigger input;

a beam splitter in operative alignment with said photon source for splitting the pulse of photons emitted from said photon source;

a first fiberoptic cable coupled to the trigger input of said first shuttered detector and positioned relative to said beam splitter so as to receive the split photon pulse and deliver a gating pulse to the trigger input of said first shuttered detector; and

a second fiberoptic cable coupled to the trigger input of said second shuttered detector and positioned relative to said beam splitter so as to receive the split photon pulse and deliver a gating pulse to the trigger input of said second shuttered detector.

21. The apparatus as defined in claim 20, wherein said second fiberoptic cable is longer than said first fiberoptic cable so as to further delay the second interval during which said second shuttered detector receives photons from said photon receiver.

22. The apparatus as defined in claim 20, wherein said first and second shuttered detectors are configured to gate on and off in about 1 ns or less.

23. The apparatus as defined in claim 20, wherein said first and second shuttered detectors include image intensifiers.

24. The apparatus as defined in claim 23, wherein photons received from said photon receiver are focussed onto a peripheral region of a photocathode of each of said image intensifiers.

25. The apparatus as defined in claim 20, and further including a fluorescence filter positioned between said photon receiver and at least one of said first and second shuttered detectors.

26. The apparatus as defined in claim 20, and further including a photodetector and a second beam splitter positioned between said photon receiver and said first and second shuttered detectors so as to transmit a portion of the photons received from said photon receiver to said photodetector.

27. The apparatus as defined in claim 20, wherein said photon source is a laser.

28. The apparatus as defined in claim 20, wherein the pulse of photons emitted from said photon source is less than about 1 ns in duration.

29. The apparatus as defined in claim 20, wherein said photon source emits near-infrared photons.

30. The apparatus as defined in claim 20, and further including a third fiberoptic cable optically coupling said photon receiver to said first and second shuttered detectors.