Method and apparatus for in vivo optical spectroscopic examination

• US 5,349,961 A
• Filed: 07/08/1993
• Issued: 09/27/1994
• Est. Priority Date: 10/14/1983
• Status: Expired due to Term

• Current Assignee: Somanetics Corporation (Medtronic Plc)
• Original Assignee: Somanetics Corporation (Medtronic Plc)
• Inventors: Stoddart, Hugh F., Lewis, Gary D.
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): GILBERT, SAMUEL G
• Application Number:
  US08/089,398
• Time in Patent Office: 446 Days
• Field of Search: 128/632, 128/633, 128/663.01, 128/664, 128/665, 128/666
• US Class Current: 600/476
• CPC Class Codes: A61B 5/0091 for mammography
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/4312 Breast evaluation or disorder diagnosis A61B5/0091 takes precedence

Abstract

Methodology and apparatus for the clinical evaluation of biological matter, in particular human anatomy, examined in situ and in vivo, by selective spectral light transmissivity. An optical probe introduces selected light spectra into the examination subject at a first position and resulting light intensity at a second position located some distance from the infusion point is measured; also, light reception preferably occurs at at least one other location, and the effective distances between these locations and the infusion point are determined. The light energy received at the distant points is quantified and conditioned by use of the effective distances from the infusion point and/or from one another, and also by contrasting the data from the two differently-located reception points, such that the resulting data quantitatively characterizes intrinsic internal tissue characteristics in an absolute sense, devoid of particular individual characteristics and variations such as skin pigmentation, boundary composition or state, etc. The methodology is especially characterized by the selection and use of particularly-located first and second light-reception positions whose locations with respect to the point at which the light spectra are introduced define particular zones of interrogation and analysis, and whose location with respect to one another may be comparatively examined (e.g., differenced) to selectively define a particular internal volume whose structure or conditional state is to be examined, quantified, and/or analyzed, all of which is accomplished on a non-intrusive in vivo basis.

Claims

1. A method of non-obtrusively and non-invasively by optical response the conditional state of physiological substance located within a particular internal volume inside a test subject, comprising the steps:

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

selecting at least first and second light-detection locations on said subject at points spaced from one another and spaced from said source by unequal first and second distances such that a first mean optical path is established 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 is established between the source and said second detection location, said second path generally defining an overall internal volume containing said particular internal volume and said first optical path generally defining a secondary internal volume located at least partially within said overall internal volume but disposed generally nearer said source location than said particular internal volume;

detecting the light resulting from said introduced light at said first and second locations and producing signals representative of such detected light; and

processing said signals to obtain optical response data which particularly characterizes selected attributes of said particular internal volume substantially without effects attributable to said secondary internal volume.

2. The method of claim 1, wherein said step of processing signals comprises differentially comparing the signals produced for said light detected at said first and second locations with respect to one another.

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

4. The method of claim 3, wherein said step of processing signals comprises subtraction of signals representative of said light detected at one of said first and second locations from signals representative of the light detected at the other such location.

5. The method of claim 1, wherein said test subject comprises an animate being having a head with a scalp and skull and containing brain tissue, and said light is introduced and detected such that said second path is sufficiently long to traverse said brain tissue while said first path is sufficiently short to traverse primarily only the scalp and skull.

6. The method of claim 5, wherein said light is introduced and detected in a manner such that said second optical path is selected to have a length which traverses a predetermined internal brain area.

7. The method of claim 1, in which said step of detecting resulting light at said first location includes using a detector located not more than about five millimeters from the source location at which said light is introduced into said subject from said source.

8. The method of claim 1, in which said step of detecting resulting light at said second location includes using a detector located not more than about thirty millimeters from the source location at which said light is introduced into said subject from said source.

9. The method of claim 8, in which said step of detecting resulting light at said first location includes using a detector located not more than about five millimeters from the source location at which said light is introduced into said subject from said source.

10. A method of appraising internal structure within selected organic bodies and materials having an outer perimeter, wherein electromagnetic energy is used as an investigative media by passing it through said perimeter and at least internal portions of said bodies and materials and producing quantitative data from such energy which characterizes composition, condition and/or physiology of a particular area inside said bodies and materials, comprising the steps of:

operatively coupling source and receiver members to a selected body or material and sending electromagnetic energy of selected wavelengths from said source member into and through the selected body or material to said receiver members;

receiving resulting electromagnetic energy from said body or material at separate and mutually-spaced first and second locations, said first location being nearer that of said source than said second location;

quantifying the resulting energy which is received at said first location as well as quantifying the resulting energy received at said second location to obtain characteristic response data values; and

using said data values for said first location to condition the said data values for said second location by modifying one such set of quantified data values as a function of the other, to thereby remove effects attributable to impingement of the electromagnetic energy upon and passage thereof through the outer perimeter of said selected body or material, whereby quantified response data valuations are obtained which characterize the composition, condition and/or physiology of a particular internal portion of said body or material on a generally intrinsic basis and which are substantially independent of characteristics attributable to said perimeter.

11. The method according to claim 10, in which said step of receiving resulting energy at the first location is carried out by using a detector which is carried with said source and disposed at a measured distance from the location thereof.

12. The method according to claim 10, in which said step of receiving resulting energy at said first location includes receiving such energy at the first location not more than about five millimeters from where said energy is introduced into said body or material.

13. Apparatus for obtaining optical response data from organic bodies which is representative of internal tissue within such bodies, including:

at least one optical probe member including a source and at least two receivers adapted for placement in operational proximity with selected areas on a perimeter of said body and adapted to pass light of selected wavelengths from said source to said receivers through said perimeter and internal tissue;

means for holding said source and receivers in predetermined relation while in their said positions of operational proximity to the selected areas on the said body;

said receivers including means for receiving the resulting light which has passed through said body at a first position with respect to said light source as well as means for receiving such light at a second position located 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; 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 by differencing the value of one such signal from that of another in pairs of correlated signal values, such that the resulting data values comprise representations of intrinsic characteristics of said internal tissue and are generally free of optical effects resulting from factors attributable to impingement of the light upon and passage thereof through the said perimeter of said body and are primarily representative of the conditioned state of a particular internal tissue volume whose location within said body is determined by the particular location and disposition of said first and second light-receiving positions relative one another.

14. Apparatus according to claim 13, in which said first receiver is positioned at a location within not more than about ten millimeters from the location of said source.

15. Apparatus according to claim 14, wherein said second receiver is positioned at a location within not more than about thirty millimeters from the location of said source.

16. Apparatus according to claim 15, wherein said light source and at least a first one of said receivers is carried by a common optical probe member.

17. Apparatus according to claim 16, wherein said common probe member further carriers a second optical receiver.

18. Apparatus according to claim 17, wherein said probe member comprises a single probe unit in which said source and said first and second receiver means are mounted.

19. In a method of conducting non-invasive clinical patient examinations by in vivo spectrometry, wherein selected wavelengths of electromagnetic energy are introduced into the patient at a first location and resultant amounts of such energy are received at at least one second location, and wherein there is a desired area to be examined which is disposed internally within the patient beyond said first and second locations, the improvement in analyzing said resultant amounts of energy to obtain data which characterizes said desired area comprising:

determining the approximate length of a generally arcuate locus extending from said first location to said second location,

measuring said received resultant amounts of energy, and

conditioning measurements of said received resultant amounts of energy as a function of a mean path length traveled by said energy between said first and second location by using said length of said locus as said mean path length.

20. The improvement defined in claim 19, wherein said step of conditioning comprises the determination of apparent spectral attenuation of said energy by scatter and absorption during traverse of said area.

21. The improvement defined in claim 19, wherein said desired area to be examined is a particular area located internally and beyond a boundary layer having a thickness t, and said step of determining locus length comprise establishing a measure of the thickness t of said boundary layer, defining a theoretical location of a virtual source disposed in alignment with said first location but spaced inwardly thereof by a distance of thickness t, defining a second theoretical location of a virtual point of reception in alignment with said second location but spaced inwardly thereof by the distance the thickness t, and using the length of a generally arcuate locus extending from said virtual source to said virtual point of reception as a measure of said mean path length.

22. The improvement defined in claim 21, wherein said step of determining locus length includes determining an approximate measure of a generally arcuately-shaped path through the thickness t of said boundary layer between said first location and said virtual source and a second length of another such path extending between said second location and said virtual point of reception.

23. The improvement defined in claim 22, further including the steps of analyzing said resultant amounts of energy received at said second location by substantially omitting the effects on said selected wavelengths of energy caused by passing through said boundary layer.

24. The improvement defined in claim 23, including the steps of receiving said resultant amounts of energy at at least two different such second locations, each located a different distance from said first location;

determining separate such arcuate path lengths for each of said at least two second locations, and using each of said separate path lengths to separately and respectively condition quantifications of resultant energy received at said at least two second locations.

25. The improvement defined in claim 24, including the steps of separately determining particular effects on different particular wavelengths within said selected wavelengths of energy caused by traversing internal tissue through which each of said at least two path lengths extend to arrive at wavelength-related pairs of data values, and contrasting at least certain of said data values in said related pairs to effectively contrast differences between the tissue traversed along such two different paths.

26. The improvement defined in claim 25, wherein said at least two second locations are disposed in the same general direction with respect to said first location and said two paths define first and second successive tissue volumes, and said step of contrasting is carried out at least in part by operatively subtracting one such data value from another to effectively isolate data pertaining to one such tissue volume from that pertaining to the other.

27. The improvement defined in claim 26, wherein said step of conditioning comprises the determination of apparent spectral attenuation of said energy by scatter and absorption during traverse of said successive tissue volumes.