Method and apparatus for spectrophotometric cerebral oximetry and the like

• US 5,482,034 A
• Filed: 08/29/1994
• Issued: 01/09/1996
• Est. Priority Date: 05/28/1993
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Original Assignee: Somanetics Corporation (Medtronic Plc)
• Inventors: Stoddart, Hugh F., Lewis, Gary D.
• Primary Examiner(s): Sykes, Angela D.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US08/297,425
• Time in Patent Office: 498 Days
• Field of Search: 128/633.4, 128/664-667, 356/35-41
• US Class Current: 600/323
• CPC Class Codes: A61B 2562/164 the sensor is mounted in or on a conformable substrate or carrier
• 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 5/6814 Head

Abstract

Spectrophotometric apparatus and related methodology, including a sensor having a source and at least two receivers of electromagnetic radiation such as red and/or near-infrared light, which is applied non-invasively to the outer periphery of a patient or other animate test subject to examine a particular internal region to which is disposed beyond a peripheral extremity of specifically indeterminant thickness lying immediately inwardly of the outer periphery of the test subject. The location of the source and detectors test are selected to be at points spaced from one another by unequal first and second distances defining first and second mean optical paths of specifically differing length, with the second such path defining a primary internal area containing the particular region to be examined, the first optical path generally defining a second internal area located in the primary internal area but substantially separate from the particular internal region to be examined, and the first such optical path including the full thickness of a predetermined typical such peripheral extremity plus at least a small portion of the physiological substance immediately therebeyond. Signals are produced which are representative of the radiation detected by the first and second receivers, and such signals are processed to obtain data which particularly characterizes selected attributes of the substance within the particular internal region, substantially without effects attributable to the secondary internal volume, The second receiver is preferably disposed about thirty to forty millimeters from the source, and the first receiver positioned not closer than about twenty millimeters therefrom.

Claims

1. A method of non-invasively examining by optical response a physiological substance located within a particular internal region inside an animate test subject having a peripheral extremity of specifically indeterminate thickness disposed generally between said internal region and the outer periphery of the subject, comprising the steps:

introducing light of selected wavelengths into said subject from a source location outside said peripheral extremity;

selecting at least first and second light-detection locations on said outer periphery at points spaced from one another and spaced from said source by unequal first and second distances to thereby define a first mean optical path extending between said source and said first detection location and a second mean optical path of a length different than that of said first mean optical path and extending between the source and said second detection location;

selecting said second path to generally define a primary internal area which contains said particular internal region and selecting said first optical path to generally define a secondary internal area which is located generally within said primary internal area but which is substantially separate from said particular internal region, and particularly selecting said first path to include the full thickness of a predetermined typical such peripheral extremity plus at least a small portion of the said physiological substance therebeyond;

detecting the light resulting from said introduced light at said first and second detection locations, producing signals representative of such detected light, and processing said signals to obtain optical response data which particularly characterizes selected attributes of said physiological substance within said particular internal region substantially without effects attributable to said secondary internal volume.

2. The method of claim 1, wherein said physiological substance comprises a highly scattering and partially absorptive media and said mean optical paths comprise arcuate curves.

3. The method of claim 1, including selecting said second optical path to traverse a generally predetermined internal brain area.

4. The method of claim 1, in which said step of selecting said first detection location comprises locating a detector not less than about twenty millimeters from the place at which said light is introduced into said subject from said source.

5. The method of claim 1, in which said step of selecting said second detection location includes locating a detector not less than about thirty millimeters from the place at which said light is introduced into said subject from said source.

6. The method of claim 5, in which said step of selecting said first detection location comprises locating a detector not less than about twenty millimeters from the place at which said light is introduced into said subject from said source.

7. The method of claim 1, in which said step of selecting said first detection location comprises locating a detector at about twenty-five to thirty millimeters from the place at which said light is introduced into said subject from said source.

8. The method of claim 1, in which said step of selecting said second detection location includes locating a detector at about thirty to forty millimeters from the place at which said light is introduced into said subject from said source.

9. The method of claim 8, in which said step of selecting said first detection location comprises locating a detector at about twenty-five to thirty millimeters from the place at which said light is introduced into said subject from said source.

10. In a method of appraising the internal structure of selected organic bodies and materials, wherein electromagnetic energy is used as an investigative media by passing it through both internal portions of said bodies and materials and overlying tissue structures and quantitative data is produced from such energy which characterizes the composition, condition and/or physiology of a particular area of said internal structure, and wherein a source and at least two receivers are used to send electromagnetic energy of selected wavelengths into and through the selected body or material and receive such energy at at least two separate and mutually-spaced external locations including a first location disposed at least somewhat nearer to said source than a second location, and the resulting energy so received is quantified to obtain characteristic response data values, the improvement comprising:

using as one of said locations a point at which the said energy there received and its corresponding data values characterize primarily said particular area of internal structure, and using as the other of said locations a point at which the energy there received and its corresponding data values characterize both said overlying tissue structure and at least a minimal amount of said internal structure which is located inwardly of said overlying structure, whereby quantified response data valuations are obtained which are assured of characterizing the internal structure at said particular area within said body or material on a generally intrinsic basis and which are independent of characteristics attributable to said overlying tissue structure.

11. The improvement according to claim 10, in which said step of using a source and at least two receivers is carried out by physically carrying said source and receivers on a single sensor member with said source and receivers disposed at measured distances from one another.

12. The improvement according to claim 10, in which said bodies and materials are the human head and brain, respectively, and said step of receiving energy at said first location includes disposing both of said receivers at points on the forehead located at least about twenty millimeters from another such point at which said energy is introduced into said head and brain.

13. The improvement according to claim 10, in which said bodies and materials are the human head and brain, respectively, and said step of receiving energy at said first location includes disposing at least one of said receivers at a point on the forehead located at about twenty-five to thirty millimeters from another such point at which said energy is introduced into said head and brain.

14. The improvement according to claim 13, in which said step of using a source and at least two receivers is carried out by physically carrying said source and receivers on a single sensor member with said source and receivers disposed at measured distances from one another.

15. Apparatus for obtaining optical response data from discrete organic bodies which is exclusively representative of internal tissue located inside the boundaries of such bodies, comprising in combination:

at least one optical sensor including a source and at least two receivers adapted for placement in optically coupled relation with selected areas on said body and adapted to pass light of selected wavelengths from said source to said receivers through such body;

means for holding said source and receivers in predetermined spatial relation while optically coupled to said selected areas of said body;

said at least two receivers including a first receiver for receiving such light from said source at a first position with respect to s;

aid light source as well as a second receiver for receiving such light at a second position located at least somewhat further away from said source than said first position, and for producing corresponding signals representative of data values for each such position which are correlated with said selected wavelengths, both said first and second positions being located so that the light received at each has traversed substantially similar portions of said boundaries and a certain amount of said internal tissue but said second position being located so that the light received there has traversed more of said internal tissue that the light received at said first location; and

means for receiving said signals and producing data values therefrom which characterize the light received at one such position as a function of corresponding light received at the other such position, such that the resulting data values comprise representations of intrinsic characteristics of said internal tissue and are free of optical effects resulting from factors attributable to passages of said light through said boundaries, said first receiver being positioned at a location which is not closer than about twenty millimeters from the location of said source.

16. Apparatus for obtaining optical response data from discrete organic bodies which is exclusively representative of internal tissue located inside the boundaries of such bodies, comprising in combination:

at least one optical sensor including a source and at least two receivers adapted for placement in optically coupled relation with selected areas on said body and adapted to pass light of selected wavelengths from said source to said receivers through such body;

means for holding said source and receivers in predetermined spatial relation while optically coupled to said selected areas of said body;

said at least two receivers including a first receiver for receiving such light from said source at a first position with respect to said light source as well as a second receiver for receiving such light at a second position located at least somewhat further away from said source than said first position, and for producing corresponding signals representative of dam values for each such position which are correlated with said selected wavelengths, both said first and second positions being located so that the light received at each has traversed substantially similar portions of said boundaries and a certain amount of said internal tissue but said second position being located so that the light received there has traversed more of said internal tissue than the light received at said first location; and

means for receiving said signals and producing data values therefrom which characterize the light received at one such position as a function of corresponding light received at the other such position, such that the resulting data values comprise representations of intrinsic characteristics of said internal tissue and are free of optical effects resulting from factors attributable to passages of said light through said boundaries, said second receiver being positioned at a location which is about thirty to forty millimeters from the location of said source.

17. Apparatus according to claim 16, in which said first receiver is positioned at a location which is not closer than about twenty millimeters from the location of said source.

18. In a method of conducting non-invasive clinical patient examinations of brain tissue by in vivo spectrometry, wherein selected wavelengths of electromagnetic energy are introduced into the brain through the scalp and skull at a first location and resultant amounts of such energy are received at a predetermined number of second locations after transmission back out through the scalp and skull, the improvement in obtaining resultant data which characterizes only brain tissue, comprising:

determining the approximate position for one of said second locations where the resultant energy received will have traversed the scalp, skull and at least a minimal amount of said brain tissue in passing from said first location to said one second location;

determining the approximate position for another of said second locations where the resultant energy received will have traversed the scalp, skull and an amount of said brain tissue greater than said at least minimal amount of brain tissue;

quantifying said resultant amounts of energy received at both said one and said other second locations; and

conditioning the said quantifications of resultant energy received at said one and said other locations by contrasting one with the other such that resultant data is obtained which generally characterizes the difference between said at least minimal amount of brain tissue and said greater amount of brain tissue.

19. The method improvement defined in claim 18, wherein said steps of determining position for said second locations includes using a representative measure of skull thickness and skull curvature at a predetermined area of the skull.

20. The method improvement defined in claim 19, wherein said predetermined area of the skull is the forehead.

21. The method improvement defined in claim 20, wherein said one and said other second locations are determined to be more closely adjacent one another than either is to said first location.