Method and apparatus for combining continuous wave and time domain optical imaging

• US 20040181153A1
• Filed: 03/12/2003
• Published: 09/16/2004
• Est. Priority Date: 03/12/2003
• Status: Active Grant

• Current Assignee: Softscan Healthcare Group Limited
• Original Assignee: Dorsky Worldwide Corp.
• Inventors: Hall, David Jonathan
• Granted Patent: US 7,720,525 B2
• Time in Patent Office: Days
• US Class Current: 600/448
• CPC Class Codes: A61B 5/0073 by tomography, i.e. reconstruction of 3D images from 2D projections A61B5/0066 takes precedence
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

There is provided methods and systems for optical imaging in a turbid medium that combine continuous wave (CW) and time domain (TD) approaches to substantially increase robustness of optical imaging as well as to reduce acquisition times associated with the TD approach. In one aspect, a method is provided that uses CW measurements to scale the values of a temporal point spread function (TPSF) to avoid physical unit mismatch problems. In another aspect, both CW and TD measurements are synergistically combined to estimate optical properties of the medium used in image reconstruction. Optical systems capable of realizing these methods are also provided.

Claims

1. A method for optical imaging of a volume of interest (VOI) in a turbid medium, the method comprising:

i) optically scanning the VOI at a plurality of source/detector geometries using continuous wave (CW) to generate CW data;

ii) optically scanning the VOI at a plurality of source/detector geometries using time-domain (TD) to generate data representing at least a portion of a measured temporal point spread function (TPSF), said TPSF data being measured from a plurality of light pulses from which a statistical average of light received as a function of time is obtained, said TPSF data yielding information about absorption and scatter within said VOI;

iii) combining information extracted from the CW data with the TPSF data to improve an accuracy of imaging using the measured TPSF data, whereby an improved image accuracy of the VOI is generated with fewer said light pulses and a shorter acquisition time by using both time-domain and continuous wave modalities.

2. The method as claimed in claim 1 wherein the step of combining comprises:

i) estimating a value of one or more optical property within the VOI using the measured TPSF;

ii) calculating an attenuation value using the estimated optical properties;

iii) comparing the calculated attenuation value with the CW data to obtain a difference value;

iv) repeating steps i) to iii) until the difference value is less than a predetermined value.

3. The method as claimed in claim 2 wherein said step of calculating comprises using a CW photon migration model.

4. The method as claimed in claim 1 wherein said step of combining comprises:

i) estimating a value of one or more optical property using TD measurements;

ii) estimating said value of one or more optical property using CW measurements;

iii) comparing said value of one or more optical property obtained by TD with said one or more optical property obtained by CW;

iv) adjusting said CW and TD estimations of said value of one or more optical property until said estimations converge to a predetermined range.

5. The method as claimed in claim 4 wherein the one or more optical property is selected from absorption coefficient, scattering coefficient and a combination thereof.

6. The method as claimed in claim 5 wherein said one or more optical properties are said absorption coefficient and said scatter coefficient and wherein prior to estimating a value of said absorption and scatter coefficients using TD measurements, said absorption coefficient is estimated using CW measurements while keeping said scatter coefficient constant.

8. The method as claimed in claim 1 wherein the TPSF and CW data are measured sequentially.

9. The method as claimed in claim 1 wherein the TPSF and CW data are measured using a gated ICCD camera, providing from each said light pulse an intensity value within at least one selected time gate.

10. The method as claimed in claim 1 wherein the TPSF and CW data are measured at a plurality of wavelengths and wherein the TPSF and attenuation value are acquired simultaneously at different wavelengths.

11. The method as claimed in claim 1 wherein a partial TPSF is measured.

12. The method as claimed in claim 11 wherein the partial TPSF comprises one or more predetermined time gate.

13. A method for optical imaging of a volume of interest (VOI) in a turbid medium, the method comprising:

i) obtaining continuous wave (CW) data to generate an image of a part of the medium comprising the VOI;

ii) localizing the VOI within the part of the medium; and

iii) obtaining time-domain (TD) data from the localized VOI to generate an image of the localized VOI.

14. A method for optical imaging of a volume of interest (VOI) in a turbid medium, the method comprising:

i) obtaining continuous wave (CW) data to generate an image of a part of the medium comprising the VOI;

ii) localizing the VOI within the part of the medium;

iii) optimizing TD image acquisition parameters using the CW data; and

iv) obtaining TD data from the VOI using the optimized TD image acquisition parameters to generate an image of the localized VOI.

15. The method as claimed in claim 14 wherein said step of optimizing comprises selecting one or more source/detector geometries used to generate CW data for use in obtaining TD data of the VOI.

16. An optical imaging system for imaging a turbid media object, the apparatus comprising:

at least one optical source for providing continuous and pulsed optical energy;

at least one optical detector for detecting optical energy and generating time-dependent and continuous data;

a source/object optical coupling for coupling said optical source to a desired position on said object;

a detector/object optical coupling for coupling said optical detector to a desired position on said object;

an acquisition controller connected to said optical source and said optical detector for collecting said time-dependent and continuous data for a plurality of source/detector geometries within a volume of interest in said object;

a continuous-wave photon migration model calculator;

a time-domain photon migration model calculator; and

an estimator using said continuous data and calculated values corresponding to said continuous data to improve a determination of optical properties of said object using said time-dependent data and calculated values corresponding to said time-dependent data.

7. The method as claimed in claim 19 further comprising a step of normalizing said measured TPSF data relative to said CW data prior to combining the information to generate dimensionless data thereby providing quicker data processing.

17. The system as claimed in claim 16 further comprising a raw TPSF data compiler for receiving a time-dependent output signal from said detector and generating raw TPSF data output.

18. The system as claimed in claim 17 wherein said TPSF data compiler comprises a TPSF data normalizer for normalizing said TPSF data with said continuous data.

19. The system as claimed in claim 16 wherein said source comprises one or more laser source.

20. The system as claimed in claim 16 wherein said source/object and detector/object optical couplings for coupling said optical source and said optical detector with said object are selected from fiber optics, free-space optics and a combination thereof.

21. The system as claimed in claim 20 wherein said source/object and said detector/object optical couplings are free-space optics and wherein said free-space optics comprise mirrors to directionally propagate light so that the light is injected and collected from desired areas on said object.

22. The system as claimed in claim 21 wherein said mirrors are mirrors galvanometers.

23. The system as claimed in claim 20 wherein said source/object and said detector/object optical couplings comprise a plurality of fiber optics and optical switches to select desired fiber optics for light injection and detection.

24. The system as claimed in claim 16 wherein said source/object optical couplings comprise a plurality of light injection ports and collection ports for coupling said optical source and said optical detector respectively with said tissue.

25. The system as claimed in claim 16 wherein said optical source provide optical energy at a plurality of wavelengths simultaneously.

26. The system as claimed in claim 25 wherein said optical detector detects optical energy at a plurality of wavelengths simultaneously.

27. The system as claimed in claims 16 wherein said acquisition controller is used to adjust said optical source intensity as a function of said detected optical energy for optimizing signal to noise ratio.

28. The system as claimed in claim 16 further comprising a display for displaying a reconstituted image of said tissue.

29. The system as claimed in claim 16 further comprising means for selecting one or more detection wavelength.

30. The system as claimed in claim 29 wherein said means for selecting is a filter.