Post-processing reduction of fixed pattern artifacts and trigger jitter in swept-source optical coherence tomography

Patent metadata

Field	Value
Publication number	US-10327631-B2
Application number	US-201614996134-A
Country	US
Kind code	B2
Filing date	Jan 14, 2016
Priority date	Jan 16, 2015
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

Disclosed herein are methods and systems for aligning swept-source optical coherence tomography (SS-OCT) spectral interferograms to a reference spectral interferogram based on signal information (e.g., amplitude or phase) at a fixed-pattern noise location to reduce residual fixed-pattern noise and improve the phase stability of SS-OCT systems.

First claim

The invention claimed is:

1. A computer-implemented method of aligning swept-source optical coherence tomography (SS-OCT) spectral interferograms, comprising:
calculating a relative wavenumber shift between an SS-OCT interferogram and a reference SS-OCT interferogram based on signal information of the SS-OCT interferogram and the reference SS-OCT interferogram at a fixed-pattern noise location, wherein the reference SS-OCT interferogram and the SS-OCT interferogram are obtained with a same interferometer;
aligning the SS-OCT interferogram to the reference SS-OCT interferogram based on the calculated relative wavenumber shift; and
generating an OCT image based on the aligned SS-OCT interferograms and outputting the generated OCT image to a display device.

2. The method of claim 1 , further comprising:
for each SS-OCT interferogram in the SS-OCT interferograms:
calculating a relative wavenumber shift between the SS-OCT interferogram and the reference SS-OCT interferogram based on signal information of the SS-OCT interferogram and the reference SS-OCT interferogram at the fixed-pattern noise location; and
aligning the SS-OCT interferogram to the reference SS-OCT interferogram based on the calculated relative wavenumber shift.

3. The method of claim 1 , wherein the signal information of the SS-OCT interferogram and the reference SS-OCT interferogram comprises amplitude or intensity information.

4. The method of claim 1 , wherein the signal information of the SS-OCT interferogram and the reference SS-OCT interferogram comprises phase information.

5. The method of claim 1 , wherein the signal information of the SS-OCT interferogram and the reference SS-OCT interferogram comprises both phase and amplitudeintensity information.

6. The method of claim 1 , wherein aligning the SS-OCT interferogram to the reference SS-OCT interferogram based on the calculated relative wavenumber shift comprises multiplying an inverse Fourier transform of the reference SS-OCT interferogram by a scaling factor, wherein the scaling factor is calculated based on the calculated relative wavenumber shift.

7. The method of claim 6 , wherein the scaling factor is calculated according to the following equation:

e

-
i

⁢

2
⁢
π

N

⁢

m
s

⁢
z

-
1

where m s is the relative wavenumber shift, N is the number of wavenumber samples in the SS-OCT interferogram, and z is a depth of the fixed-pattern noise location.

8. The method of claim 1 , wherein calculating the relative wavenumber shift between the SS-OCT interferogram and the reference SS-OCT interferogram comprises calculating the relative wavenumber shift from the phases, amplitudes or complex values of I r (z f ), I s (z f ) and I sr (z f ), where z f is a depth of the residual fixed-pattern noise location I r (z f ) is an inverse Fourier transform of the reference SS-OCT interferogram at depth z f , I s (z f ) is an inverse Fourier transform of the SS-OCT interferogram of interest at depth z f , and I sr (z f )=I s (z f )−I r (z f ).

9. The method of claim 1 , wherein calculating the relative wavenumber shift between the SS-OCT interferogram and the reference SS-OCT interferogram comprises introducing wavenumber shifts (k-shifts) in the SS-OCT interferogram and searching for a k-shift that minimizes an amplitude of the SS-OCT interferogram at the fixed pattern noise location, and wherein the relative wavenumber shift comprises a k-shift that minimizes the amplitude of the SS-OCT interferogram at the fixed pattern noise location.

10. The method of claim 9 , wherein the amplitude of the SS-OCT interferogram at the fixed pattern noise location comprises a sum over a few pixels centered at a peak of fixed pattern noise at the fixed pattern noise location.

11. The method of claim 1 , wherein calculating the relative wavenumber shift between the SS-OCT interferogram and the reference SS-OCT interferogram comprises calculating the relative wavenumber shift using only phase information at the residual fixed pattern noise location.

12. The method of claim 1 , wherein the relative wavenumber shift (m s ) between the SS-OCT interferogram and the reference SS-OCT interferogram is calculated according to the following equation:
m s =angle[ I s ( z f )]/ I r ( z f )]* N /(2 πz f )

where z f is a depth of the residual fixed-pattern noise location, N is the number of wavenumber samples in the SS-OCT interferogram, I r (z f ) is an inverse Fourier transform of the reference SS-OCT interferogram at depth z f , I s (z f ) is an inverse Fourier transform of the SS-OCT interferogram of interest at depth z f , and angle[] is a phase extraction function.

13. The method of claim 1 , further comprising removing the first and last one or more wavenumber sample points from the aligned SS-OCT interferograms.

14. The method of claim 1 , further comprising performing background subtraction, Gaussian window spectral shaping, numerical dispersion compensation, and/or inverse Fourier transforms on each aligned SS-OCT interferogram.

15. The method of claim 1 , wherein the fixed-pattern noise location is around a zero frequency or close to a maximum imaging range of an SS-OCT system used to acquire the SS-OCT interferograms.

16. The method of claim 1 , further comprising introducing an artificial fixed-pattern noise artifact at the fixed-pattern noise location prior to aligning the SS-OCT interferogram and the reference SS-OCT interferogram.

17. The method of claim 1 , wherein the reference SS-OCT interferogram comprises a single interferogram.

18. The method of claim 1 , wherein the reference SS-OCT interferogram comprises a single background interferogram.

19. The method of claim 1 , wherein the OCT image comprises a structural OCT image or a Doppler OCT image.

20. A system for aligning swept-source optical coherence tomography (SS-OCT) spectral interferograms, comprising:
an SS-OCT system comprising a swept-source laser, the SS-OCT system configured to acquire SS-OCT interferograms;
a logic subsystem; and
a data holding subsystem comprising machine-readable instructions stored thereon that are executable by the logic subsystem to perform the steps of claim 1 .

21. The system of claim 20 , wherein the swept-source laser has a central wavelength of approximately 1050 nm.

Assignees

• Huang David
• Liu Gangjun
• Univ Oregon Health & Science

Inventors

• Huang David
• Liu Gangjun

Classifications

• G01B9/02004

  using frequency scans · CPC title

• A61B3/102 Primary

  for optical coherence tomography [OCT] · CPC title

• G01B9/02091

  Tomographic interferometers, e.g. based on optical coherence · CPC title

• G01B9/0207

  Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer · CPC title

• A61B3/1233

  for measuring blood flow, e.g. at the retina · CPC title