Methods, systems and computer program products for optical coherence tomography (OCT) using automatic dispersion compensation

• US 20070258094A1
• Filed: 04/27/2007
• Published: 11/08/2007
• Est. Priority Date: 04/28/2006
• Status: Active Grant

• Current Assignee: Bioptigen, Inc. (Danaher Corporation)
• Original Assignee: Bioptigen, Inc. (Danaher Corporation)
• Inventors: Brown, William, Izatt, Joseph, Buckland, Eric
• Granted Patent: US 7,719,692 B2
• Time in Patent Office: Days
• US Class Current: 356/456
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: G01B 9/02044 Imaging in the frequency domain, e.g. by using a spectrometer
• CPC Class Codes: G01B 9/02083 characterised by particular signal processing and presentation
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

Methods, systems and computer program products for generating parameters for software dispersion compensation in optical coherence tomography (OCT) systems are provided. Raw spectral interferogram data is acquired for a given lateral position on a sample and a given reference reflection. A trial spectral phase corresponding to each wavenumber sample of the acquired spectral interferogram data is postulated. The acquired raw spectral data and the postulated trial spectral phase data are assembled into trial complex spectrum data. Trial A-scan data is computed by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of a result.

Claims

1. A method for generating parameters for software dispersion compensation in optical coherence tomography (OCT) systems, comprising:

acquiring raw spectral interferogram data for a given lateral position on a sample and a given reference reflection;

postulating a trial spectral phase corresponding to each wavenumber sample of the acquired spectral interferogram data;

assembling the acquired raw spectral data and the postulated trial spectral phase data into trial complex spectrum data; and

computing trial A-scan data by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of a result.

2. The method of claim 1:

wherein the raw spectral interferogram data is denoted M(k); and

wherein postulating comprises postulating a trial phase corresponding to each wavenumber sample of M(k) according to the following equation;

φ

(k)=a(k−

k₀)+b(k−

k₀)²+c(k−

k₀)³+d(k−

k₀)⁴,

wherein k₀ is the central wavenumber of a light source of the OCT system, and wherein a, b, c and d are parameters to be optimized and represent respective first, second, third, and fourth-order corrections to be made to a phase of the acquired raw spectral interferogram data.

3. The method of claim 2, wherein assembling comprises assembling the acquired raw spectral interferogram data and the trial spectral phase data into the trial complex spectrum data according to the following equation:

S(k)=M(k)e<sup>iφ

(k)</sup>,

wherein e is the base of natural logarithms and i is the square root of −

1.

4. The method of claim 3, wherein computing comprises computing trial A-scan data by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of the result according to the following equation:

|s(z)|=|I.F.T.{S(k)}|,

wherein the result |s(z)| is the real-valued trial A-scan representing the depth-resolved reflectivity of the sample at a given lateral location, blurred by dispersion mismatch between interferometer arms but corrected by the postulated trial spectral phase.

5. The method of claim 4, further comprising repeating the postulating, assembling and computing steps to optimize the values of a, b, c and d based on optimization of an image quality metric applied to the trial A-scan data |s(z)|.

6. The method of claim 1, wherein the result is depth independent.

7. A method for generating parameters for software dispersion compensation in optical coherence tomography (OCT) systems, comprising:

initiating optimization of parameters for software dispersion compensation;

optimizing the parameters in less than about 15 seconds; and

acquiring an image using the optimized parameters without increasing processing time.

8. The method of claim 7, wherein optimizing the parameters comprises optimizing the parameters in from about 3.0 to about 5.0 seconds.

9. The method of claim 7, wherein optimizing further comprises optimizing through an entire depth of the sample.

10. An optical coherence tomography (OCT) system, comprising:

an imaging system with automatic parameter optimization, the imaging system being configured to;

acquire raw spectral interferogram data for a given lateral position on a sample and a given reference reflection;

postulate a trial spectral phase corresponding to each wavenumber sample of the acquired spectral interferogram data;

assemble the acquired raw spectral data and the postulated trial spectral phase data into trial complex spectrum data; and

compute trial A-scan data by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of a result.

11. The system of claim 10, wherein the raw spectral interferogram data is denoted M(k), the imaging system being further configured to postulate a trial phase corresponding to each wavenumber sample of M(k) according to the following equation:

φ

(k)=a(k−

k₀)+b(k−

k₀)²+c(k−

k₀)³+d(k−

k₀)⁴,

wherein k₀ is the central wavenumber of a light source of the OCT system, and wherein a, b, c and d are parameters to be optimized and represent respective first, second, third, and fourth-order corrections to be made to a phase of the acquired raw spectral interferogram data.

12. The system of claim 11, wherein the imaging system is further configured to assemble the acquired raw spectral interferogram data and the trial spectral phase data into the trial complex spectrum data according to the following equation:

S(k)=M(k)e<sup>iφ

(k)</sup>,

wherein e is the base of natural logarithms and i is the square root of −

1.

13. The system of claim 12, wherein the imaging system is further configured to compute trial A-scan data by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of the result according to the following equation:

|s(z)|=|I.F.T.{S(k)}|,

wherein the result |s(z)| is the real-valued trial A-scan representing the depth-resolved reflectivity of the sample at a given lateral location, blurred by dispersion mismatch between interferometer arms but corrected by the postulated trial spectral phase.

14. The system of claim 13, wherein the imaging system is configured to repeatedly postulate, assemble and compute steps to optimize the values of a, b, c and d based on optimization of an image quality metric applied to the trial A-scan data |s(z)|.

15. The system of claim 10, wherein the result is depth independent.

16. An optical coherence tomography (OCT) system, comprising:

an imaging system with automatic parameter optimization, the imaging system being configured to;

initiate optimization of parameters for software dispersion compensation;

optimize the parameters in less than about 15 seconds; and

acquire an image using the optimized parameters without increasing processing time.

17. The system of claim 16, wherein the imaging system is further configured to optimize the parameters in from about 3.0 to about 5.0 seconds.

18. The system of claim 16, wherein the imaging system is configured to optimize through an entire depth of the sample.

19. A computer program product for generating parameters for software dispersion compensation in optical coherence tomography (OCT) systems, the computer program product comprising:

computer readable storage medium having computer readable program code embodied in the medium, the computer readable program code comprising;

computer readable program code configured to acquire raw spectral interferogram data for a given lateral position on a sample and a given reference reflection;

computer readable program code configured to postulate a trial spectral phase corresponding to each wavenumber sample of the acquired spectral interferogram data;

computer readable program code configured to assemble the acquired raw spectral data and the postulated trial spectral phase data into trial complex spectrum data; and

computer readable program code configured to compute trial A-scan data by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of a result.

20. The computer program product of claim 19, wherein the raw spectral interferogram data is denoted M(k), the computer program product further comprising computer readable program code configured to postulate a trial phase corresponding to each wavenumber sample of M(k) according to the following equation:

φ

(k)=a(k−

k₀)+b(k−

k₀)²+c(k−

k₀)³+d(k−

k₀)⁴,

wherein k₀ is the central wavenumber of a light source of the OCT system, and wherein a, b, c and d are parameters to be optimized and represent respective first, second, third, and fourth-order corrections to be made to a phase of the acquired raw spectral interferogram data.

21. The computer program product of claim 20, further comprising computer readable program code configured to assemble the acquired raw spectral interferogram data and the trial spectral phase data into the trial complex spectrum data according to the following equation:

S(k)=M(k)e<sup>iφ

(k)</sup>,

wherein e is the base of natural logarithms and i is the square root of −

1.

22. The computer program product of claim 21, further comprising computer readable program code configured to compute trial A-scan data by performing an inverse Fourier transform on the trial complex spectrum data and determining the magnitude of the result according to the following equation:

|s(z)|=|I.F.T.{S(k)}|,

wherein the result |s(z)| is the real-valued trial A-scan representing the depth-resolved reflectivity of the sample at a given lateral location, blurred by dispersion mismatch between interferometer arms but corrected by the postulated trial spectral phase.

23. The computer program product of claim 22, further comprising computer readable program code configured to repeat the postulating, assembling and computing steps to optimize the values of a, b, c and d based on optimization of an image quality metric applied to the trial A-scan data |s(z)|.

24. The computer program product of claim 19, wherein the result is depth independent.

25. A computer program product for generating parameters for software dispersion compensation in optical coherence tomography (OCT) systems, the computer program product comprising:

computer readable program code configured to initiate optimization of parameters for software dispersion compensation;

computer readable program code configured to optimize the parameters in less than about 15 seconds; and

computer readable program code configured to acquire an image using the optimized parameters without increasing processing time.

26. The computer program product of claim 25, further comprising computer readable program code configured to optimize the parameters in from about 3.0 to about 5.0 seconds.

27. The computer program product of claim 25, further comprising computer readable program code configured to optimize through an entire depth of the sample.