Speckle reduction in optical coherence tomography images

Patent metadata

Field	Value
Publication number	US-10478058-B2
Application number	US-201515528080-A
Country	US
Kind code	B2
Filing date	Nov 19, 2015
Priority date	Nov 20, 2014
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

Abstract

An optical coherence tomography (OCT) image composed of a plurality of A-scans of a structure is analyzed by defining, for each A-scan, a set of neighboring A-scans surrounding the A-slices scan. Following an optional de-noising step, the neighboring A-scans are aligned in the imaging direction, then a matrix X is formed from the aligned A-scans, and matrix completion is performed to obtain a reduced speckle noise image.

First claim

What is claimed is:

1. A computer-implemented method of enhancing an optical coherence tomography (OCT) image composed of a plurality of A-scans, each A-scan being indicative of a structure imaged in a predefined direction, the A-scans being grouped as one or more B-scans, the method comprising, for each A-scan:
(a) defining a respective neighborhood comprising a set of A-scans surrounding said each A-scan, the set of A-scans forming a two-dimensional as viewed in the predefined direction;
(b) aligning the set of A-scans in the respective neighborhood to said each A-scan of the respective neighborhood;
(c) using the aligned A-scans to form a first matrix X, respective columns of the first matrix X being the aligned A-scans; and
(d) seeking a second matrix which minimizes a cost function indicative of the difference between the first matrix X and the second matrix, the second matrix being constrained to obey a complexity constraint.

2. A method according to claim 1 in which the complexity constraint is that the second matrix is constrained to have a rank no higher than a predefined value.

3. A method according to claim 1 in which the complexity constraint is that, representing the second matrix as the sum of a low rank matrix L and a sparse matrix S, the complexity constraints being that the low rank matrix L is constrained to have a rank less than a first predetermined value, and the sparse matrix S is constrained to have a number of non-zero elements less than a second predetermined value.

4. A method according to claim 1 comprising a prior operation of noise reduction in the plurality of A-scans.

5. A method according to claim 4 in which the noise-reduction is a speckle reduction anisotropic diffusion algorithm.

6. A method according to claim 1 wherein operation (b) is performed by:
defining a first A-scan group consisting of one or more A-scans including said each A-scan of the respective neighborhood; and
for each neighbouring A-scan:
(i) defining a second respective A-scan group, the second respective A-scan group consisting of one or more A-scans including the neighbouring A-scan;
(ii) seeking a respective translation value which, if the one or more A-scans of the respective second A-scan group are translated in the predefined direction by the translation value, minimises a difference between the first A-scan group and the second A-scan group; and
(iii) translating the neighbouring A-scan by the respective translation value.

7. A method according to claim 6 in which operation (b) is performed by a block matching algorithm.

8. A method according to claim 7 wherein the block matching algorithm is a diamond search algorithm.

9. A method according to claim 7 , wherein the two-dimensional array is a rectangular region or an elliptical region.

10. A computer system comprising a processor and a memory device configured to store program instructions operative, when performed by the processor, to cause the processor to perform a method of enhancing an optical coherence tomography (OCT) image composed of a plurality of A-scans, each A-scan being indicative of a structure imaged in a predefined direction, the A-scans being grouped as one or more B-scans, the method comprising, for each A-scan:
(a) defining a respective neighborhood comprising a set of A-scans surrounding said each A-scan, the set of A-scans forming a two-dimensional array as viewed in the predefined direction;
(b) aligning the set of A-scans the respective neighborhood to said each A-scan of the respective neighborhood;
(c) using the aligned A-scans to form a first matrix X, respective columns of the first matrix X being the aligned A-scans; and
(d) seeking a second matrix which minimizes a cost function indicative of the difference between the first matrix X and the second matrix, the second matrix being constrained to obey a complexity constraint.

11. A non-transitory computer program product, storing program instructions operative, when performed by a processor, to cause the processor to perform a method of enhancing an optical coherence tomography (OCT) image composed of a plurality of A-scans, each A-scan being indicative of a structure imaged in a predefined direction, the A-scans being grouped as one or more B-scans, the method comprising, for each A-scan:
(a) defining a respective neighborhood comprising of a set of A-scans surrounding said each A-scan, the set of A-scans forming a two-dimensional array as viewed in the predefined direction;
(b) aligning the set of A-scans in the respective neighborhood to said each A-scan of the respective neighborhood;
(c) using the aligned A-scans to form a first matrix X, respective columns of the first matrix X being the aligned A-scans; and
(d) seeking a second matrix which minimizes a cost function indicative of the difference between the first matrix X and the second matrix, the second matrix being constrained to obey a complexity constraint.

Assignees

• Agency Science Tech & Res
• Kk Topcon

Inventors

• Cheng Jun
• Liu Jiang
• Wong Wing Kee Damon
• Akiba Masahiro

Classifications

• G06T5/50

  using two or more images, e.g. averaging or subtraction · CPC title

• G01B9/02091

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

• G01B9/02083

  characterised by particular signal processing and presentation · CPC title

• G01B9/02082

  Caused by speckles · CPC title

• A61B3/0025

  characterised by electronic signal processing, e.g. eye models · CPC title