Object imaging using diffuse light

• US 5,917,190 A
• Filed: 07/25/1996
• Issued: 06/29/1999
• Est. Priority Date: 10/29/1993
• Status: Expired due to Term

• Current Assignee: Trustees Of The University Of Pennsylvania (University of Pennsylvania)
• Original Assignee: Trustees Of The University Of Pennsylvania (University of Pennsylvania)
• Inventors: O'Leary, Maureen, Chance, Britton, Yodh, Arjun G., Boas, David A.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US08/637,645
• Time in Patent Office: 1,069 Days
• Field of Search: 356/375, 250/458.1
• US Class Current: 250/458.1
• CPC Class Codes: A61B 5/0091 for mammography
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B
• CPC Class Codes: G01N 21/6428 Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" in vivo A61B5/00; immunoassay G01N33/53
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/89 for mapping or imaging

Abstract

Imaging tumors using diffuse light. An imaging system includes a source of diffuse light for generating oscillatory diffuse photon density waves to illuminate an object, a detector for detecting diffuse photon density waves interacting with the object, and a computer interfaced with the detector for processing data corresponding to the photon density waves detected to determine at least a position of the object. In one embodiment, the turbid medium and the object have associated therewith at least one diffusion coefficient and the diffuse photon density waves which illuminate the object refract around the object as a result of their interaction with it, thereby producing a distorted wavefront that allows the computer to construct an image of the object. In another embodiment, a fluorescent object produces re-radiated diffuse photon density waves which allow the object to be imaged.

Claims

1. A system for imaging an object in a turbid medium using diffuse light comprising:

source means for generating oscillatory diffuse photon density waves to illuminate the object;

detection means for detecting diffuse photon density waves produced as a result of the diffuse photon density waves interacting with the object;

processing means interfaced with the detection means for processing data corresponding to the photon density waves detected by the detection means to determine at least a position of the object;

said turbid medium and the object have associated therewith at least one diffusion coefficient and the diffuse photon density waves which illuminate the object diffracts around or refracts through the object as a result of their interaction with it, thereby producing a distorted wavefront such that after the detection means detects the distorted wavefront the processing means determines the diffusion coefficient of the turbid medium and the object.

2. The system recited in claim 1 wherein the processing means constructs phase and amplitude contours corresponding to propagation of the distorted wavefront and further determines at least the position of the object from the phase and amplitude contours, thereby imaging the object.

3. The system recited in claim 2 further comprising display means interfaced with the processing means for displaying the position of the object.

4. The system recited in claim 3 wherein the source means comprises at least one laser and the detection means comprises an optical fiber interfaced with a photomultiplier tube.

5. The system recited in claim 1 wherein the object is fluorescent and the diffuse photon density waves which have a first wavelength cause the object to fluoresce, thereby producing re-radiated diffuse photon density waves having a second wavelength such that after the detection means detects the re-radiated diffuse photon density waves, the processing means can image the object.

6. The system recited in claim 5 wherein the source means comprises a plurality of lasers oriented around the object which alternately irradiate the object with the diffuse photon density waves of the first wavelength to cause the object to fluoresce.

7. The system recited in claim 6 wherein the detection means comprises an optical fiber that is placed in proximity to the object and a photomultiplier tube interfaced to the optical fiber.

8. The system recited in claim 7 further comprising switch means interfaced with each of the plurality of lasers for alternately and sequentially turning on and off each laser and radio frequency driving means interfaced through the switch means with the lasers for driving the lasers to produce the diffuse photon density waves of the first wavelength.

9. The system recited in claim 8 further comprising display means interfaced with the processing means for displaying the position of the object produced by the processing means.

10. The system recited in claim 5 wherein the source means comprises a plurality of lasers each having a spatial location with respect to the object and each laser being modulated at all times during imaging at a different frequency in a frequency range around a specified frequency, thereby producing a power spectrum associated with each spatial location around the object.

11. The system recited in claim 10 further comprising analysis means interfaced with the detection means and the processing means for analyzing the power spectrums associated with each spatial location to determine the position of the object.

12. The system recited in claim 11 further comprising display means interfaced with the processing means for displaying the image of the object.

13. The system recited in claim 5 wherein the source means comprises a phased-array.

14. The system recited in claim 13 wherein the phased-array comprises at least two lasers that are substantially one hundred and eighty degrees out of phase with each other, thereby producing the diffuse photon density waves having the first wavelength which interfere destructively to produce an amplitude null line and a one hundred and eighty degree phase shift across the null line.

15. The system recited in claim 14 wherein the phased-array scans the null line so that the processing means can produce the image.

16. A method of imaging an object in a turbid medium using diffuse light comprising the steps of:

illuminating the object with oscillatory diffuse photon density waves;

detecting diffuse density waves which are produced as a result of the diffuse photon density waves interacting with the object; and

determining at least the position of the object in the turbid medium by analyzing the detected diffuse photon density waves, wherein the turbid medium and the object have associated therewith at least one diffusion coefficient and the diffuse photon density waves which illuminate the object refract around the object as a result of the interaction with it, thereby producing a distorted wavefront which is analyzed to determine the diffusion coefficient of the turbid medium and the object.

17. The method recited in claim 16 wherein the determining step comprises the steps of constructing phase contours corresponding to propagation of the distorted wavefront and determining at least the position of the object from the phase contours, thereby imaging the object.

18. The method recited in claim 17 further comprising the step of displaying the image of the object.

19. The method recited in claim 16 wherein the object is fluorescent and the diffuse photon density waves which have a first wavelength cause the object to fluoresce, thereby producing re-radiated diffuse photon density waves having a second wavelength such that detecting the re-radiated diffuse photon density waves the object to be imaged.

20. The method recited in claim 19 wherein the illuminating step comprises the step of alternately irradiating the object with at least two sources of diffuse photon density waves of the first wavelength to cause the object to fluoresce.

21. The method recited in claim 19 wherein the illuminating step comprises the step of continuously illuminating the object with at least two sources of diffuse photon density waves each having a spatial location with respect to the object, wherein each source has associated therewith a frequency in a frequency range around a specified frequency, thereby producing a power spectrum associated with each spatial location around the object.

22. The method recited in claim 19 wherein the illuminating step comprises the steps of irradiating the object with a phased-array and scanning an amplitude null line to produce the image of the object.

23. A system for imaging an object in a turbid medium comprising:

source means for illuminating the object with oscillatory diffuse photon density waves of a first specified wavelength, whereby the object will fluoresce re-radiate diffuse photon density waves of a second wavelength after being illuminated with the oscillatory diffuse photon density waves of the first specified wavelength;

detection means for detecting the re-radiate diffuse photon density waves of the second wavelength; and

processing means interfaced with the detection means for processing data corresponding to the re-radiated diffuse photon density waves of the second wavelength to determine at least the position of the object in the turbid medium.

24. The system recited in claim 23 wherein the source means comprises a plurality of lasers oriented around the object which alternately irradiated the object with the diffuse photon density waves of the first wavelength to cause the object to fluoresce.

25. The system recited in claim 24 wherein the detection means comprises an optical fiber that is placed in proximity to the object and a photomultiplier tube interfaced to the optical fiber.

26. The system recited in claim 25 further comprising switch means interfaced with each of the plurality of lasers for alternately and sequentially turning on and off each laser and radio frequency driving means interfaced through the switch means with the lasers for driving the lasers to produce the diffuse photon density waves of the first wavelength.

27. The system recited in claim 26 further comprising display means interfaced with the processing means for displaying the image of the object produced by the processing means.

28. The system recited in claim 23 wherein the source means comprises a plurality of lasers each having a spatial location with respect to the object and each laser is modulated at all times during imaging at a different frequency in a frequency range around a specified frequency, thereby producing a power spectrum associated with each spatial location around the object.

29. The system recited in claim 28 further comprising analysis means interfaced with the detection means and the processing means for analyzing the power spectrums associated with each spatial location to determine the position of the object.

30. The system recited in claim 29 further comprising display means interfaced with the processing means for displaying the image of the object.

31. The system recited in claim 23 wherein the source means comprises a phased-array.

32. The system recited in claim 31 wherein the phased-array comprises at least two lasers that are substantially one hundred and eighty degrees out of phase with each other, thereby producing the diffuse photon density waves having the first wavelength which interfere destructively to produce an amplitude null line and a one hundred and eighty degree phase shift at points equidistant from the lasers.

33. The system recited in claim 32 wherein the phased-array scans the null line so that the processing means can produce the image.

34. A method of imaging an object in a turbid medium comprising the steps of:

illuminating the object with oscillatory diffuse photon density waves of a first specified wavelength;

allowing the object to fluoresce, thereby reradiating a diffuse photon density waves having a second wavelength;

detecting the re-radiated diffuse photon density waves having the second wavelength; and

analyzing the photon density waves having the second wavelength to determine at least the position of the object based on its image in the turbid medium.

35. The method recited in claim 34 wherein the illuminating step comprises the step of alternately irradiating the object with at least two sources of diffuse photon density waves of the first wavelength to cause the object to fluoresce.

36. The method recited in claim 34 wherein the illuminating step comprises the step of continuously illuminating the object with at least two sources of diffuse photon density waves each having a spatial location with respect to the object, wherein each source has associated therewith a frequency in a frequency range around a specified frequency, thereby producing a power spectrum associated with each spatial location around the object.

37. The method recited in claim 34 wherein the illuminating step comprises the steps of irradiating the object with a phased-array and scanning an amplitude null line to produce the image of the object.

38. A system for imaging an object in a turbid medium wherein the turbid medium and object have a diffusion coefficient associated therewith comprising:

source means for illuminating the object with oscillatory diffuse photon density waves, whereby a distorted wavefront of diffuse photon density waves is created by refraction of the oscillatory diffuse photon density waves refracting around the object;

detection means for detecting the distorted wavefront of diffuse photon density waves refracted around the object;

processing means interfaced with the detection means for constructing phase contours corresponding to propagation of the distorted wavefront of diffuse photon density waves to determine at least the position of the object in the turbid medium; and

display means interfaced with the processing means for displaying the image of the object.

39. The system recited in claim 38 wherein the source means comprises at least one laser and the detection means comprises an optical fiber interfaced with a photomultiplier tube.

40. A method of imaging an object in a turbid medium wherein the turbid medium and the object have a diffusion coefficient associated therewith comprising the steps of:

illuminating the object with oscillatory diffuse photon density waves;

allowing the diffuse photon density waves to refract around the object throughout the turbid medium thereby producing a distorted wavefront of diffuse photon density waves;

detecting the distorted wavefront of diffuse photon density waves;

analyzing the distorted wavefront of diffuse photon density waves to determine at least the position of the object in the turbid medium utilizing the steps of constructing phase contours corresponding to propagation of the distorted wavefront and determining at least the position of the object from the phase contours, thereby imaging the object; and

displaying the image of the object.