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Apparatus for monitoring metabolism in body organs

  • US 4,321,930 A
  • Filed: 09/18/1980
  • Issued: 03/30/1982
  • Est. Priority Date: 06/28/1977
  • Status: Expired due to Term
First Claim
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1. A spectrophotometric reflectance apparatus for measuring in situ, in vivo, non-invasively, atraumatically, harmlessly, rapidly and continuously a local metabolic oxygen dependent activity of a selected portion of the body such as the brain of a body where such activity bears a measureable relation to an oxygen dependent absorption characteristic of the selected portion for a particular wavelength of light transmitted therethrough, comprising:

  • (a) circuitry means including;

    (i) a plurality of near-infrared light sources located external of the body and having light emissions of different wavelengths in the 700 to 1300 nanometer spectral range and of an intensity below the level damaging to the body and said selected portion but sufficient to be detectable by a light sensor after transmission through any skin, bone and tissue included in an optical transmission-reflectance path including said selected portion thereof and extending for several centimeters between points of light entry and exit laterally spaced several centimeters apart and located on contiguous skin surface areas of the body and after scattering in and deep reflectance from said selected portion along said path, said emissions including at least one measuring wavelength and at least one reference wavelength within said spectral range, each said measuring wavelength being selected such that said selected portion exhibits a selected absorption therefore, the extent of which is dependent upon a specific state of a local metabolic, oxygen dependent activity of said selected portion; and

    (ii) means operatively associated with said light sources to produce emissions representing at least one said measuring wavelength and at least one said reference wavelength within said spectral range for transmission along said path to said selected portion and at levels of intensity below that which would be damaging to the body and said selected portion;

    (b) first optical cable coupling means for receiving transmitting and directing the output light emissions of said light sources at said measuring and reference wavelengths to a light entry point proximate said body;

    (c) a detachable, body mountable apparatus associated with said circuitry means including;

    (i) a flexible, elongated support member adapted to be releasably secured to the body proximate a said selected portion of the body having a selected set of said light entry and exit points, said support member being adapted to provide ambient light shielding over said light entry and exit points and to conform to the curvature and shape of the body at the location thereof;

    (ii) a mounting structure secured to said support member and adapted to deform in shape in correspondence with the curvature assumed by said support member when secured to the body;

    (iii) a first preformed light guide means mounted in said mounting structure and optically coupled to said first optical cable means and having an optical face for light exit adapted to be mated in a substantially pressed fit relation with said selected point of light entry for entry of light in said wavelengths to be transmitted, deeply reflected and scattered along said path and to said selected portion;

    (iv) a first preformed light detector assembly mounted in said mounting structure proximate said first light guide means and having first light collector means adapted to be mated in a substantially pressed fit relation with said selected point of light entry for receiving deeply penetrating light emissions reflected directly back from any skin, bone and tissue at or within a few millimeters of said selected point of light entry; and

    (v) a second preformed light detector assembly mounted in said mounting structure and having second light collecting means spaced several centimeters away from said first collector means and adapted to be mated in a substantially pressed fit relation with said selected point of light exit for receiving deeply penetrating light emissions reflected and scattered to said selected point of light exit from said selected portion of said body;

    (d) second coupling means operatively coupling the output of said first light detector assembly to said circuitry means;

    (e) third coupling means operatively coupling the output of said second light detector assembly to said circuitry means; and

    (f) processing means operatively associated with said circuitry means adapted to produce from the outputs of said first and second light detector assemblies an electrical output signal corrected for changes in blood volume of said skin, bone and tissue during the measuring cycle and representing the difference in absorption of said measuring and reference wavelengths by said selected body portion as a function of the state of said local metabolic oxygen dependent activity and further adapted to convert said electrical output signal to a signal providing a substantially continuous and rapid measure of said activity.

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