In vivo structural and flow imaging

• US 8,180,134 B2
• Filed: 09/18/2007
• Issued: 05/15/2012
• Est. Priority Date: 09/26/2006
• Status: Active Grant

• Current Assignee: Oregon Health & Science University
• Original Assignee: Oregon Health & Science University
• Inventors: Wang, Ruikang K.
• Primary Examiner(s): Mis, David
• Application Number:
  US12/442,928
• Publication Number:
  US 20100027857A1
• Time in Patent Office: 1,701 Days
• Field of Search: 382128-134
• US Class Current: 382/131
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: A61B 5/0066 Optical coherence imaging
• CPC Class Codes: A61B 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01F 1/663 by measuring Doppler frequency shift

Abstract

Embodiments of the present invention include but are not limited to methods and systems for optical coherence imaging. A method for optical coherence imaging may comprise scanning a sample with an incident beam from a light source; detecting one or more spectral interference signals from the sample; modulating the one or more spectral interference signals by a linear translation of a reference mirror while scanning the sample in a cross-sectional direction; and obtaining at least one image of the sample from the modulated one or more spectral interference signals, the at least one image including a selected one of a full range structural image of the sample and a separated structure/flow image of the sample.

Claims

1. A method of imaging, comprising:

scanning a sample with an incident beam from a light source;

detecting one or more spectral interference signals from the sample and a reference mirror;

modulating the one or more spectral interference signals at a constant frequency while scanning the sample in a cross-sectional direction (B scan); and

obtaining at least one image of the sample from the modulated one or more spectral interference signals, the at least one image including a full range structural image of the sample or a separated structure/flow image of the sample.

2. The method of claim 1, wherein said modulating comprises modulating the one or more spectral interference signals at a constant frequency.

3. The method of claim 1, wherein said obtaining at least one image comprises:

separating structure information of the sample and flow information of the sample; and

obtaining a first image and a second image, the first image including the structure information and the second image including the flow information.

4. The method of claim 1, wherein said scanning comprises scanning the sample with the incident beam in x and λ

directions to obtain a first two-dimensional (2-D) spectral interferogram data set, said x direction including one or more columns and said λ

direction including one or more rows.

5. The method of claim 4, wherein said obtaining the at least one image comprises:

calculating discrete analytic functions, along the x-direction and row by row in the λ

direction of the first 2-D data set, to obtain a complex valued function of the first 2-D data set; and

converting the complex valued function of the first 2-D data set from a spectral domain to a time domain, column by column in the x direction, to obtain the at least one image of the sample.

6. The method of claim 5, wherein said calculating discrete analytic functions comprises Hilbert-transforming the first 2-D data set.

7. The method of claim 5, wherein said converting the complex valued function of the first 2-D data set comprises Fourier-transforming the complex valued function of the first 2-D data set.

8. The method of claim 4, further comprising scanning the sample with the incident beam in the x and λ

directions along y direction to obtain a second 2-D spectral interferogram data set, said first and second 2-D data sets forming a three-dimensional spectral interferogram data set.

9. The method of claim 1, wherein said obtaining at least one image comprises obtaining the separated structure/flow image of the sample, and wherein the flow image of the sample is indicative of a direction of flow of the sample.

10. The method of claim 9, wherein a collection of all the B scans of the sample when the reference mirror moves toward the incident beam gives the flow away from the incident beam direction.

11. The method of claim 9, wherein a collection of all the B scans of the sample when the mirror moves away from the incident beam gives the flow toward the incident beam direction.

12. The method of claim 1, wherein the modulating comprises modulating the one or more spectral interference signals by a linear translation of the reference mirror.

13. The method of claim 1, wherein the modulating comprises modulating the one or more spectral interference signals by offsetting the incident beam.

14. The method of claim 1, wherein the modulating comprises modulating the one or more spectral interference signals by stretching an optical fiber providing the incident beam.

15. The method of claim 1, wherein the modulating at a constant frequency comprises modulating at a frequency having a constant value and a constant polarity.

16. A method for imaging, comprising:

scanning a flowing sample with an incident beam from a light source;

detecting one or more spectral interference signals from the flowing sample and a reference mirror;

modulating digitally the one or more spectral interference signals from the flowing sample at a constant frequency;

obtaining an image from the modulated one or more spectral interference signals, the image indicative of a direction of flow of the flowing sample.

17. The method of claim 16, wherein the digital modulation comprises:

obtaining a cross-sectional data point from a flowing sample at a dimension of (x,λ

), h(λ

,x), at any one time;

performing an interpolation for h(λ

,x) from λ

space to k space along the λ

dimension column by column to obtain h(k,x);

calculating a Fourier transform column by column along the λ

dimension, resulting in H(z,x) that possesses positive and negative spaces in z;

forming two functions from H(z,x) forcing negative space of H(z,x) equal to zero to form H1(z,x), and forcing positive space of H(z,x) equal to zero to form H2(z,x);

modulating H1(z,x) and H2(z,x) digitally with a frequency of f₀ along the x dimension to obtain modulated signals H1′

(z,x) and H2′

(z,x);

performing an inverse Fourier transformation to H1′

(z,x) and H2′

(z,x) along the z dimension and take only real parts or imaginary parts of results that form h1(k,x) and h2(k,x);

calculating an analytic function along the x dimension row by row in the λ

dimension to obtain a complex valued function of data from the inverse Fourier transformation operation resulting in ĥ

1(k,x) and ĥ

2(k,x);

performing a Fourier transformation of ĥ

1(k,x) and ĥ

2(k,x) along the k dimension to obtain complex optical images, H1(z,x) and H2(z,x) and obtain magnitudes of results; and

separating |H1(z,x)| and |H2(z,x)| at zero delay line (z=0) to form four images of the flowing sample.

18. The method of claim 17, wherein two of said four images represent structural images of the flowing sample.

19. The method of claim 17, wherein one of said four images represents a flow image indicative of flow moving toward an incident probe beam.

20. The method of claim 17, wherein one of said four images represents a flow image indicative of flow moving away from an incident probe beam.

21. The method of claim 16, wherein the digital modulation comprises:

obtaining a cross-sectional data point from a flowing sample at a direction of (x,λ

), h(λ

,x), at any one time;

performing an interpolation for h(λ

,x) from λ

space to k space along an λ

direction column by column to obtain h(k,x);

calculating a Fourier transform row by row along an x direction, resulting in H(k,f) having positive and negative spaces in f;

forming three functions from H(k,f) by;

multiplying a first rectangle function t1(k,f) to form H1(k,f);

multiplying a second rectangle function t2(k,f) to form H2(k,f); and

multiplying a third rectangle function t3(k,f) to form H3(k,f);

calculating analytic functions along an f direction row by row in k direction to obtain a complex valued function of the three functions resulting in ĥ

1(k,x), ĥ

2(k,x), and ĥ

3(k,x);

performing a Fourier transformation of ĥ

1(k,x), ĥ

2(k,x), and ĥ

3(k,x) along the k direction to obtain the complex optical images, H1(z,x), H2(z,x), and H3(z,x) and obtain magnitudes of the images; and

separating |H1(z,x)|, |H2(z,x)| and |H3(z,x)|at zero delay line (z=0) to form six images of the flowing sample.

22. The method of claim 21, wherein two of said six images represent structural images of the flowing sample.

23. The method of claim 21, wherein two of said six images represent flow images of the sample without indication of flow directions.

24. The method of claim 21, wherein one of said six images represents a flow image indicative of flow moving toward an incident probe beam.

25. The method of claim 21, wherein one of said six images represents a flow image indicative of flow moving away from an incident probe beam.

26. A system for in vivo imaging, comprising:

an optical coherence tomography apparatus; and

one or more processors coupled to the apparatus and adapted to cause the apparatus to;

scan a sample with an incident beam from a light source;

detect one or more spectral interference signals from the sample and a reference mirror;

modulate the one or more spectral interference signals by a linear translation of a reference mirror while scanning the sample in a cross-sectional direction; and

obtain at least one image of the sample from the modulated one or more spectral interference signals, the at least one image including a full range structural image of the sample or a separated structure/flow image of the sample.

27. The system of claim 26, wherein the optical coherence tomography apparatus includes a reference arm including a mirror mounted on a modulating device for modulating the one or more spectral interference signals.

28. The system of claim 26, wherein the one or more processors are adapted to cause the apparatus to scan the sample with the incident beam in x and λ

directions to obtain a first two-dimensional (2-D) spectral interferogram data set, said x direction including one or more columns and said λ

direction including one or more rows.

29. The system of claim 28, wherein the one or more processors are adapted to cause the apparatus to obtain the at least one image by:

calculating discrete analytic functions, along the x-direction and row by row in the λ

direction of the first 2-D data set, to obtain a complex valued function of the first 2-D data set; and

converting the complex valued function of the first 2-D data set from a spectral domain to a time domain, column by column in the x direction, to obtain the at least one image of the sample.