Path constrained spectrophotometer and method for determination of spatial distribution of light or other radiation scattering and absorbing substances in a radiation scattering medium

• US RE36,044 E
• Filed: 05/08/1997
• Issued: 01/12/1999
• Est. Priority Date: 12/24/1991
• Status: Expired due to Term

• Current Assignee: JB IP Acquisitions LLC
• Original Assignee: David A. Benaron
• Inventors: Benaron, David A.
• Primary Examiner(s): CASLER, BRIAN L
• Application Number:
  US08/853,498
• Time in Patent Office: 614 Days
• Field of Search: 600/310, 600/473, 600/476, 250/332, 250/343, 250/339, 356/39, 356/40, 356/41, 356/432, 378/87
• US Class Current: 600/310
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

A spectrophotometer for providing an image of a radiation scattering medium having one or more radiation attenuating constituents is disclosed herein. The spectrophotometer includes a light source for illuminating the scattering medium with electromagnetic radiation of at least one wavelength. In one embodiment a time-gated detector serves to detect, during a predefined detection interval, the electromagnetic radiation having traversed a distribution of path lengths during propagation through a region of the medium. A photon counting apparatus or the like measures the intensity of the detected portion of the electromagnetic radiation, wherein the measured intensity is a function of attenuation of the region within the medium. A display apparatus is operative to generate the image in accordance with the measured intensity.

Claims

1. A spectrophotometer for providing an image of a radiation scattering medium having one or more radiation attenuating constituents, comprising:

light source means for illuminating said medium from a source location at a time t₀ with electromagnetic radiation of at least one wavelength, said electromagnetic radiation propagating through said medium over a plurality of paths;

means for detecting, during a set of detection windows commencing at selected times relative to time t₀, portions of said electromagnetic radiation emerging from said medium at a first detection location after having propagated through said medium from said source location to said first detection location over a corresponding set of paths of selected length;

intensity measuring means for measuring intensity of each of said detected portions of electromagnetic radiation during said detection windows wherein said measured intensities are a function of attenuation of said region; and

means for generating said image based upon said intensities measured during each of said detection windows and upon corresponding ones of said paths of selected length.

2. The spectrophotometer of claim 1 wherein said means for detecting includes an array of detectors for detecting, at a first plurality of locations proximate said medium, said electromagnetic radiation having propagated through said plurality of paths through said medium.

3. The spectrophotometer of claim 2 wherein said plurality of locations includes a two-dimensional array of locations, and wherein said means for generating an image includes means for generating a two-dimensional image based on said measured intensities of radiation detected by said array of detectors.

4. The spectrophotometer of claim 1 wherein said means for detecting includes a scanning detector for detecting, at a first plurality of locations proximate said medium, said electromagnetic radiation having propagated through said plurality of of paths through said medium.

5. The spectrophotometer of claims 2 or 4 wherein said light source means includes means for illuminating said medium from a second plurality of locations proximate said medium.

6. The spectrophotometer of claim 1 wherein said intensity measuring means includes means for comparing said intensities measured during each of said detection windows with a reference intensity corresponding to measured intensity of radiation propagating through said medium along a reference path.

7. The spectrophotometer of claim 1 wherein said light source means includes a laser for emitting a pulse of electromagnetic radiation, and wherein said detecting means includes a time-gated detector actuated during a predefined detection interval subsequent to said emission of said pulse.

8. The spectrophotometer of claim 1 wherein said light source means includes laser means for generating electromagnetic radiation at a plurality of selectable wavelengths.

9. The spectrophotometer of claim 1 wherein said means for detecting includes a time-gated detector for producing detection signals only during multiple predefined detection intervals in response to said electromagnetic radiation incident thereon.

10. The spectrophotometer of claim 1 further including means for computing concentration, C, of one or more of said radiation attenuating constituents in accordance with the expression,

11. The spectrophotometer of claim 1 wherein said means for generating said image includes means for generating an image representing concentration of said one or more radiation attenuating constituents.

12. The spectrophotometer of claim 1 wherein said detecting means includes means for detecting portions of said electromagnetic radiation having traversed non-linear paths during propagation through said medium, said nonlinear paths being of substantially different path length than a linear transmission path through said medium.

13. The spectrophotometer of claim 1 wherein said means for generating said image includes means for formulating a time-intensity relationship in accordance with said intensities measured during each of said detection windows, and deriving an image parameter using said time-intensity relationship and said paths of selected length.

14. A spectrophotometer for providing an image of a radiation scattering medium having one or more radiation attenuating constituents, comprising:

means for illuminating said medium with electromagnetic radiation of at least one wavelength, and for modulating intensity of said electromagnetic energy in accordance with a phase-modulation waveform;

means for detecting portions of said electromagnetic radiation propagating through a region of said medium;

means for determining a phase shift Of said phase-modulation waveform associated with each of said detected portions of said electromagnetic radiation, each of said phase shifts corresponding to a function of the distribution of radiation path lengths through said region of said medium;

means for measuring intensity of each of said detected portions of electromagnetic radiation wherein each of said measured intensities corresponds to attenuation of said region; and

means for generating said image in accordance with said measured intensities and phase shifts.

15. The electrophotometer of claim 14 wherein said means for illuminating includes means for generating an illumination beam and a reference beam.

16. The spectrophotometer of claim 15 wherein said means for determining phase shift includes means for comparing said reference beam with portions of said illumination beam incident upon said means for detecting.

17. The spectrophotometer of claim 14 wherein said means for detecting includes an array of detectors for detecting, at a first plurality of locations proximate said medium, said electromagnetic radiation having propagated through a plurality of regions of said medium.

18. The spectrophotometer of claim 14 wherein said means for detecting includes a scanning detector for detecting, at a first plurality of locations proximate said medium;

said electromagnetic radiation having propagated through a plurality of regions of said medium.

19. The spectrophotometer of claims 17 or 18 wherein said means for illuminating includes light source means for illuminating said medium at a second plurality of locations proximate said medium.

20. The spectrophotometer of claim 14 wherein said means for illuminating includes laser means for generating said electromagnetic radiation at a plurality of selectable wavelengths.

21. A method for providing an image of a radiation scattering medium having one or more radiation attenuating constituents, comprising the steps of:

illuminating said medium with electromagnetic radiation of at least one wavelength from a source location at a time t₀, said electromagnetic radiation propagating through a region of said medium over a plurality of paths;

detecting, during a set of detection windows commencing at selected times relative to time t₀, portions of said electromagnetic radiation emerging from said medium at a first detection location after having propagated through said medium from said source location to said first detection location over a corresponding set of paths of selected length;

measuring intensity of each of said detected portions of electromagnetic radiation wherein said measured intensities are a function of attenuation of said region; and

generating said image based upon said intensities measured during each of said detection windows at said first detection location and upon corresponding ones of said paths of selected length.

22. The method of claim 21 further including the step of detecting, at a first plurality of locations proximate said medium, said electromagnetic radiation having propagated over said plurality of paths through said medium.

23. The method of claim 22 further including the step of illuminating said medium from a second plurality of locations proximate said medium.

24. The method of claim 22 wherein said fist plurality of locations includes a two-dimensional array of locations, and wherein said step of generating said image includes the step of generating a two-dimensional image based on measured intensities of radiation detected by said array of detectors.

25. The method of claim 21 wherein said step of measuring intensity includes the step of comparing said intensities measured during each of said detection windows with a reference intensity corresponding to measured intensity of radiation propagating through said medium along a reference path.

26. The method of claim 21 wherein said step of illuminating further includes the step of emitting a pulse of electromagnetic radiation, and wherein said step of detecting is performed during a predefined detection interval selected to begin at a predefined time subsequent to said emission of said pulse:

thereby resulting in detection of said electromagnetic radiation having traversed one of said paths of selected length.

27. The method of claim 21 wherein said step of illuminating includes the step of generating said electromagnetic radiation at a plurality of selectable wavelengths.

28. The method of claim 21 further including the step of computing concentration, C, of one or more of said radiation attenuating constituents in accordance with the expression,

29. The method of claim 21 wherein said step of generating said image includes the step of generating an image representing concentration of said one or more radiation attenuating constituents.

30. The method of claim 21 wherein said step of detecting includes the step of detecting electromagnetic energy having traversed one or more nonlinear paths during propagation through said medium, said one or more nonlinear paths being of substantially different path length than a linear transmission path through said medium.

31. The method of claim 21 wherein said step of generating said image includes the step of formulating a time-intensity relationship in accordance with said intensities measured during each of said detection windows, and the step of deriving an image parameter using said time-intensity relationship and said paths of selected length.

32. A method for providing an image of a radiation scattering medium having one or more radiation attenuating constituents, comprising the steps of:

illuminating said medium with electromagnetic radiation of at least one wavelength, and modulating intensity of said electromagnetic energy in accordance with a phase-modulation waveform;

detecting portions of said electromagnetic radiation propagating through a region of said medium;

determining a phase shift of said phase-modulation waveform associated with each of said detected portions of said electromagnetic radiation, each of said phase shifts corresponding to a function of the distribution of radiation path lengths through said region of said medium;

measuring intensity of each of said detected portions of electromagnetic radiation wherein each of said measured intensities corresponds to attenuation of said region; and

generating said image in accordance with said measured intensities and phase shifts.

33. The method of claim 32 wherein said step of illuminating includes the step of generating an illumination beam and a reference beam.

34. The method of claim 33 wherein said step of determining phase shift includes the step of comparing said reference beam with portions of said illumination beam.

35. The method of claim 34 further including the step of detecting, at a first plurality of locations proximate said medium, said electromagnetic radiation having propagated through a plurality of regions of said medium.

36. The method of claim 35 further including the step of illuminating said medium at a second plurality of locations proximate said medium.

37. The method of claim 32 wherein said step of illuminating includes the step of generating electromagnetic radiation at a plurality of selectable wavelengths.

38. A spectrophotometer for providing an image of a radiation scattering medium having one or more radiation attenuating constituents, comprising:

light source means for illuminating said medium with electromagnetic radiation characterized by a first time-intensity relationship, said electromagnetic radiation propagating through said medium over a plurality of paths;

detection means for detecting said electromagnetic radiation having propagated through said medium over at least one path of one or more selected lengths, said detection means including means for identifying a second-tine intensity relationship characterizing said detected electromagnetic energy having propagated over said at least one path of said one or more selected lengths; and

means for generating an image based on said one or more selected lengths and said second time-intensity relationship. .Iadd.

39. A spectrophotometer for providing a measurement of a radiation scattering medium having one or more radiation attenuating constituents, comprising:

light source means for illuminating said medium from a source location at a time t₀ with electromagnetic radiation of at least one wavelength, said electromagnetic radiation propagating through said medium over a plurality of paths;

means for detecting, during a set of detection windows commencing at selected times relative to time t₀, portions of said electromagnetic radiation emerging from said medium at a first detection location after having propagated through said medium from said source location to said first detection location over a corresponding set of paths of selected length;

intensity measuring means for measuring intensity of each of said detected portions of electromagnetic radiation during said detection windows wherein said measured intensities are a function of attenuation of said region; and

means for generating a result representative of said measurement based upon said intensities measured during each of said detection windows and upon corresponding ones of said paths of selected length. .Iaddend..Iadd.40. A spectrophotometer for providing a measurement of a radiation scattering medium having one or more radiation attenuating constituents, comprising;

means for illuminating said medium with electromagnetic radiation of at least one wavelength, and for modulating intensity of said electromagnetic energy in accordance with a phase-modulation waveform;

means for detecting portions of said electromagnetic radiation propagating through a region of said medium;

means for determining a phase shift of said phase-modulation waveform associated with each of said detected portions of said electromagnetic radiation, each of said phase shifts corresponding to a function of the distribution of radiation path lengths through said region of said medium;

means for measuring intensity of each of said detected portions of electromagnetic radiation wherein each of said measured intensities corresponds to attenuation of said region; and

means for generating a result representative of said measurement in accordance with said measured intensities and phase shifts. .Iaddend..Iadd.41. A method for providing a measurement of a radiation scattering medium having one or more radiation attenuating constituents, comprising the steps of;

illuminating said medium with electromagnetic radiation of at least one wavelength from a source location at a time t₀, said electromagnetic radiation propagating through a region of said medium over a plurality of paths;

detecting, during a set of detection windows commencing at selected times relative to time t₀, portions of said electromagnetic radiation emerging from said medium at a first detection location after having propagated through said medium from said source location to said first detection location over a corresponding set of paths of selected length;

measuring intensity of each of said detected portions of electromagnetic radiation wherein said measured intensities are a function of attenuation of said region; and

generating a result representative of said measurement based upon said intensities measured during each of said detection windows and upon corresponding ones of said paths of selected length. .Iaddend..Iadd.42. A method for providing a measurement of a radiation scattering medium having one or more radiation attenuating constituents, comprising the steps of;

illuminating said medium with electromagnetic radiation of at least one wavelength, and modulating intensity of said electromagnetic energy in accordance with a phase-modulation waveform;

detecting portions of said electromagnetic radiation propagating through a region of said medium;

determining a phase shift of said phase-modulation waveform associated with each of said detected portions of said electromagnetic radiation, each of said phase shifts corresponding to a function of the distribution of radiation path lengths through said region of said medium;

measuring intensity of each of said detected portions of electromagnetic radiation wherein

each of said measured intensities corresponds to attenuation of said region, and generating a result representative of said measurement in accordance with said measured intensities and phase shifts. .Iaddend..Iadd.43. A spectrophotometer for providing a measurement of a radiation scattering medium having one or more radiation attenuating constituents, comprising;

light source means for illuminating said medium with electromagnetic radiation characterized by a first time-intensity relationship, said electromagnetic radiation propagating through said medium over a plurality of paths;

detection means for detecting said electromagnetic radiation having propagated through said medium over at least one path of one or more selected lengths, said detection means including means for identifying a second time-intensity relationship characterizing said detected electromagnetic energy having propagated over said at least one path of said one or more selected lengths; and

means for generating a result representative of said measurement based on said one or more selected lengths and said second time-intensity relationship. .Iaddend..Iadd.44. The spectrophotometer of claim 39, 40 or 43 wherein said means for generating a result includes means for generating a result selected from the group comprising absorbance, scattering, concentration, and oxygenation of said one or more radiation attenuating constituents. .Iaddend..Iadd.45. The method of claim 41 or 42 wherein said step of generating a result includes generating a result selected from the group comprising absorbance, scattering, concentration, and oxygenation of said one or more radiation attenuating constituents. .Iaddend.