Reconstruction of optical coherent tomography (OCT) images of morphological features

1. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device obtained via scanning a reference path length relative to a signal path length of a signal path in the interferometer of the OCT device where the target object is located at one end of the signal path, comprising:

obtaining different OCT images of the target object under different reference path lengths;

processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images; and

processing the derivative to extract improved image information of the target object to reduce an effect of a signal decay due to scattering of light in the target object,

wherein obtaining different OCT images of the target object under different reference path lengths comprises:

obtaining different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate; and

obtaining different OCT images of the target object at different reference path lengths at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinate below a surface of the target object, and

wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images comprises:

averaging a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image;

obtaining a normalized OCT image intensity of a position in the averaged B-scan image by dividing a signal intensity of the position in the averaged B-scan image by a signal intensity at a surface of the target object;

calculating a gradient value of the normalized OCT image intensity in the signal path length direction by subtracting a normalized OCT image intensity in a next depth to the normalized OCT image intensity; and

obtaining the derivative with respect to the signal path length by dividing the gradient value of the normalized OCT image intensity by double actual distance of one pixel.

2. The method of claim 1 , wherein processing the derivative to extract improved image information of the target object comprises:

iteratively calculating derivatives with respect to the signal path length through all positions of the averaged B-scan image; and

reconstructing an OCT slope image having improved image information of the target object from the derivatives with respect to the signal path length through all positions of the averaged B-scan image.

3. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device obtained via scanning a reference path length relative to a signal path length of a signal path in the interferometer of the OCT device where the target object is located at one end of the signal path, comprising:

obtaining different OCT images of the target object under different reference path lengths;

processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images; and

processing the derivative to extract improved image information of the target object to reduce an effect of a signal decay due to scattering of light in the target object,

wherein obtaining different OCT images of the target object under different reference path lengths comprises:

obtaining different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate; and

obtaining different OCT images of the target object at different reference path lengths at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinate below a surface of the target object, and

wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images comprises:

selecting a B-scan image among the different OCT images of the target object under different reference path lengths at different locations shifted in position represented by x and y coordinates;

removing noise in the selected B-scan image to obtain a denoised B-scan image;

obtaining a normalized OCT image intensity by dividing a signal intensity of the denoised B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

selecting an A-scan signal of a point at the denoised B-scan image with normalized OCT image intensity;

dividing the signal path length into a plurality of smaller segments;

selecting data of the A-scan signal in the signal depth direction at a segment containing a depth z;

calculating the derivative of the A-scan signal in the segment with the selected data at the segment containing the depth z; and

calculating iteratively derivatives of the A-scan signal through all segments in the signal path.

4. The method of 3 , wherein removing noise in the selected B-scan image to obtain the denoised B-scan image comprises:

removing noise in the selected B-scan image by a Gaussian filter to obtain the denoised B-scan image.

5. The method of 4 , wherein the Gaussian filter has a size of 15 pixels×15 pixels and a standard deviation of 1.

6. The method of claim 3 , wherein the plurality of smaller segments of the signal path length has a length of 5 pixels.

7. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device obtained via scanning a reference path length relative to a signal path length of a signal path in the interferometer of the OCT device where the target object is located at one end of the signal path, comprising:

obtaining different OCT images of the target object under different reference path lengths;

processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images; and

processing the derivative to extract improved image information of the target object to reduce an effect of a signal decay due to scattering of light in the target object,

wherein obtaining different OCT images of the target object under different reference path lengths comprises:

obtaining different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate; and

obtaining different OCT images of the target object at different reference path lengths at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinate below a surface of the target object, and

wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images comprises:

averaging a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image;

obtaining a normalized OCT image intensity in the averaged B-scan image by dividing a signal intensity of an averaged B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

obtaining a gradient value of the normalized OCT image intensity in the signal path length direction by subtracting an OCT signal intensity in a next depth to the OCT signal intensity;

calculating an attenuation coefficient by dividing the gradient value by double actual distance of one pixel and then multiplying −1; and

obtaining an enhanced attenuation coefficient by dividing the attenuation coefficient by the normalized OCT image intensity.

8. The method of claim 7 , wherein processing the derivative to extract improved image information of the target object comprises:

iteratively calculating enhanced attenuation coefficients through all position of the averaged B-scan image; and

reconstructing an enhanced OCT slope image having improved image information of the target object from the enhanced attenuation coefficients through all position of the averaged B-scan image.

9. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device obtained via scanning a reference path length relative to a signal path length of a signal path in the interferometer of the OCT device where the target object is located at one end of the signal path, comprising:

obtaining different OCT images of the target object under different reference path lengths;

processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images; and

processing the derivative to extract improved image information of the target object to enhance image information of boundaries of heterogeneous layers in the target object,

wherein obtaining different OCT images of the target object under different reference path lengths comprises:

obtaining different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate; and

obtaining different OCT images of the target object at different reference path lengths at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinate below a surface of the target object,

wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images comprises:

averaging a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image;

obtaining a normalized OCT image intensity of a position in the averaged B-scan image by dividing a signal intensity of the position in the averaged B-scan image by a signal intensity at a surface of the target object;

calculating a gradient value of the normalized OCT image intensity in the signal path length direction by subtracting a normalized OCT image intensity in a next depth to the normalized OCT image intensity; and

obtaining the derivative with respect to the signal path length by dividing the gradient value of the normalized OCT image intensity by double actual distance of one pixel.

10. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device obtained via scanning a reference path length relative to a signal path length of a signal path in the interferometer of the OCT device where the target object is located at one end of the signal path, comprising:

obtaining different OCT images of the target object under different reference path lengths;

processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images; and

processing the derivative to extract improved image information of the target object to enhance image information of boundaries of heterogeneous layers in the target object,

wherein obtaining different OCT images of the target object under different reference path lengths comprises:

obtaining different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate; and

obtaining different OCT images of the target object at different reference path lengths at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinate below a surface of the target object,

wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images comprises:

selecting a B-scan image among the different OCT images of the target object under different reference path lengths at different locations shifted in position represented by x and y coordinates;

removing noise in the selected B-scan image to obtain a denoised B-scan image;

obtaining a normalized OCT image intensity by dividing a signal intensity of the denoised B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

selecting an A-scan signal of a point at the denoised B-scan image with normalized OCT image intensity;

dividing the signal path length into a plurality of smaller segments;

selecting data of the A-scan signal in the signal depth direction at a segment containing a depth z;

calculating the derivative of the A-scan signal in the segment with the selected data at the segment containing the depth z; and

calculating iteratively derivatives of the A-scan signal through all segments in the signal path.

11. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device obtained via scanning a reference path length relative to a signal path length of a signal path in the interferometer of the OCT device where the target object is located at one end of the signal path, comprising:

obtaining different OCT images of the target object under different reference path lengths;

processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images; and

processing the derivative to extract improved image information of the target object to enhance image information of boundaries of heterogeneous layers in the target object,

wherein obtaining different OCT images of the target object under different reference path lengths comprises:

obtaining different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate; and

obtaining different OCT images of the target object at different reference path lengths at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinate below a surface of the target object,

wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images comprises:

averaging a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image;

obtaining a normalized OCT image intensity in the averaged B-scan image by dividing a signal intensity of an averaged B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

obtaining a gradient value of the normalized OCT image intensity in the signal path length direction by subtracting an OCT signal intensity in a next depth to the OCT signal intensity;

calculating an attenuation coefficient by dividing the gradient value by double actual distance of one pixel and then multiplying −1; and

obtaining an enhanced attenuation coefficient by dividing the attenuation coefficient by the normalized OCT image intensity.

12. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device obtained via scanning a reference path length relative to a signal path length of a signal path in the interferometer of the OCT device where the target object is located at one end of the signal path, comprising:

obtaining different OCT images of the target object (1) at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate, and (2) at different reference path lengths at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinates below a surface of the target object;

processing OCT images of the target object obtained at different locations shifted in position represented by x and y coordinates to obtain an averaged B-scan image;

obtaining a normalized OCT image intensity by dividing a signal intensity of an averaged B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

obtaining a gradient value of the normalized OCT image intensity with respect to the z coordinate; and

using gradient values of the normalized OCT image intensities at different locations to construct an OCT slope image of the target image.

13. The method of claim 12 , wherein obtaining a gradient value of the normalized OCT image intensity with respect to the z coordinate comprises:

calculating the gradient value of the normalized OCT image intensity by subtracting a normalized OCT image intensity in a next depth to the normalized OCT image intensity.

14. An optical coherence tomography (OCT) device, comprising:

an optical interferometer having a signal path in which a target object is located to receive light of a signal beam and a reference path for carrying a reference light beam to cause a spatial overlap the reflected or back scattered signal light from the target object and the reference light beam to produce an OCT optical signal beam containing different OCT images of the target object that are obtained (1) at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinates in the signal path, and (2) at different reference path lengths of the reference path at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinates below a surface of the target object; and

an imaging processing device which processes the OCT images of the target object obtained at different locations shifted in position represented by x and y coordinates to obtain an averaged B-scan image, obtains a normalized OCT image intensity by dividing a signal intensity of an averaged B-scan OCT image at each position represented by x and y coordinates by a signal intensity at a surface of the target object, obtains a gradient value of the normalized OCT image intensity with respect to the z coordinate, and uses gradient values of the normalized OCT image intensities at different at different locations to construct an OCT slope image of the target image.

15. The OCT device of claim 14 , wherein the image processing device obtaining a gradient value of the normalized OCT image intensity with respect to the z coordinate comprises:

calculating the gradient value of the normalized OCT image intensity with respect to the z coordinate by subtracting a normalized OCT image intensity in a next depth to the normalized OCT image intensity.

16. The OCT device of claim 15 , wherein the image processing device using gradient values of the normalized OCT image intensities at different at different locations to construct an OCT slope image of the target image comprises:

obtaining a derivative with respect to the signal path length by dividing the gradient value of the normalized OCT image intensity by double actual distance of one pixel;

iteratively calculating derivatives with respect to the signal path length through all positions of the averaged B-scan image; and

reconstructing the OCT slope image having improved image information of the target object from the derivatives with respect to the signal path length through all positions of the averaged B-scan image.

17. An optical coherence tomography (OCT) device, comprising:

an optical interferometer having a signal path in which a target object is located to receive light of a signal beam and a reference path for carrying a reference light beam to cause a spatial overlap the reflected or back scattered signal light from the target object and the reference light beam to produce an OCT optical signal beam containing different OCT images of the target object that are obtained (1) at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinates in the signal path, and (2) at different reference path lengths of the reference path at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinates below a surface of the target object; and

an imaging processing device which:

selects a B-scan image among the different OCT images of the target object under different reference path lengths at different locations shifted in position represented by x and y coordinates;

removes noise in the selected B-scan image to obtain a denoised B-scan image;

obtains a normalized OCT image intensity by dividing a signal intensity of the denoised B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

selects an A-scan signal of a point at the denoised B-scan image with normalized OCT image intensity;

divides the signal path length into a plurality of smaller segments;

selects data of the A-scan signal in the signal depth direction at a segment containing a depth z;

calculates a derivative of the A-scan signal in the segment with the selected data at the segment containing the depth z;

calculates iteratively derivatives of the A-scan signal through all segments in the signal path;

calculates iteratively derivatives with respect to the signal path length through all positions of the denoised B-scan image; and

reconstructs an OCT slope image having improved image information of the target object from the derivatives with respect to the signal path length through all positions of the denoised B-scan image.

18. The OCT device of 17 , wherein removing noise in the selected B-scan image to obtain the denoised B-scan image comprises:

removing noise in the selected B-scan image by a Gaussian filter to obtain the denoised B-scan image.

19. The OCT device of 17 , wherein removing noise in the selected B-scan image to obtain the denoised B-scan image comprises:

removing noise in the selected B-scan image by averaging a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image.

20. An optical coherence tomography (OCT) device, comprising:

an optical interferometer having a signal path in which a target object is located to receive light of a signal beam and a reference path for carrying a reference light beam to cause a spatial overlap the reflected or back scattered signal light from the target object and the reference light beam to produce an OCT optical signal beam containing different OCT images of the target object that are obtained (1) at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinates in the signal path, and (2) at different reference path lengths of the reference path at each of the different locations to obtain 3-dimensional image information of the target object at the different locations and at different depths with different z coordinates below a surface of the target object; and

an imaging processing device which:

averages a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image;

obtains a normalized OCT image intensity in the averaged B-scan image by dividing a signal intensity of the averaged B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

obtains a gradient value of the normalized OCT image intensity in the signal path length direction;

obtains an attenuation coefficient from the gradient value;

obtains an enhanced attenuation coefficient by dividing the attenuation coefficient by the normalized OCT image intensity;

iteratively calculates enhanced attenuation coefficients through all position of the averaged B-scan image; and

reconstructs an enhanced OCT slope image having improved image information of the target object from the enhanced attenuation coefficients through all position of the averaged B-scan image.

21. The OCT device of 20 , wherein obtaining a gradient value of the normalized OCT image intensity in the signal path length direction comprises:

obtaining a gradient value of the normalized OCT image intensity in the signal path length direction by subtracting an OCT signal intensity in a next depth to the OCT signal intensity.

22. The OCT device of 20 , wherein obtaining an attenuation coefficient from the gradient value comprises:

obtaining an attenuation coefficient from the gradient value by dividing the gradient value by double actual distance of one pixel and then multiplying −1.

23. An optical coherence tomography (OCT) device, comprising:

an optical interferometer having a signal path in which a target object is located to receive light of a signal beam and a reference path for carrying a reference light beam to cause a spatial overlap the reflected or back scattered signal light from the target object and the reference light beam to produce an OCT optical signal beam containing different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object and at different z coordinates in the signal path to obtain 3-dimensional image information of the target object at the different x, y and z locations below a surface of the target object; and

an imaging processing device which processes the OCT images of the target object obtained at different locations shifted in position represented by x and y coordinates to obtain an averaged B-scan image, obtains a normalized OCT image intensity by dividing a signal intensity of an averaged B-scan OCT image at each position represented by x and y coordinates by a signal intensity at a surface of the target object, obtains a gradient value of the normalized OCT image intensity with respect to the z coordinate, and uses gradient values of the normalized OCT image intensities at different locations to construct an OCT slope image of the target image.

24. The OCT device of claim 23 , wherein the image processing device obtaining a gradient value of the normalized OCT image intensity with respect to the z coordinate comprises:

calculating the gradient value of the normalized OCT image intensity with respect to the z coordinate by subtracting a normalized OCT image intensity in a next depth to the normalized OCT image intensity.

25. The OCT device of claim 23 , wherein the image processing device using gradient values of the normalized OCT image intensities at different at different locations to construct an OCT slope image of the target image comprises:

obtaining a derivative with respect to the signal path length by dividing the gradient value of the normalized OCT image intensity by double actual distance of one pixel;

iteratively calculating derivatives with respect to the signal path length through all positions of the averaged B-scan image; and

reconstructing the OCT slope image having improved image information of the target object from the derivatives with respect to the signal path length through all positions of the averaged B-scan image.

26. The OCT device of claim 23 , comprising:

a broadband light source that produces light for the signal beam and the reference light beam in the optical interferometer.

27. An optical coherence tomography (OCT) device, comprising:

an optical interferometer having a signal path in which a target object is located to receive light of a signal beam and a reference path for carrying a reference light beam to cause a spatial overlap the reflected or back scattered signal light from the target object and the reference light beam to produce an OCT optical signal beam containing different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object and at different z coordinates in the signal path to obtain 3-dimensional image information of the target object at the different x, y and z locations below a surface of the target object; and

an imaging processing device which:

averages a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image;

obtains a normalized OCT image intensity in the averaged B-scan image by dividing a signal intensity of the averaged B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

obtains a gradient value of the normalized OCT image intensity in the signal path length direction;

obtains an attenuation coefficient from the gradient value;

obtains an enhanced attenuation coefficient by dividing the attenuation coefficient by the normalized OCT image intensity;

iteratively calculates enhanced attenuation coefficients through all position of the averaged B-scan image; and

reconstructs an enhanced OCT slope image having improved image information of the target object from the enhanced attenuation coefficients through all position of the averaged B-scan image.

28. The OCT device of 27 , wherein obtaining a gradient value of the normalized OCT image intensity in the signal path length direction comprises:

obtaining a gradient value of the normalized OCT image intensity in the signal path length direction by subtracting an OCT signal intensity in a next depth to the OCT signal intensity.

29. The OCT device of claim 27 , comprising:

a broadband light source that produces light for the signal beam and the reference light beam in the optical interferometer.

30. A method for extracting image information from images of a target object in an optical coherence tomography (OCT) device, comprising:

obtaining different OCT images of the target object at different depths into the target object;

processing the different OCT images to obtain a derivative with respect to the depth of image information of the different OCT images; and

processing the derivative to extract improved image information of the target object to reduce an effect of a signal decay due to scattering of light in the target object,

wherein obtaining different OCT images of the target object at different depths into the target object comprises:

obtaining different OCT images of the target object at different locations shifted in position represented by x and y coordinates along a direction substantially perpendicular to a direction of incidence of light into the target object represented by z coordinate; and

obtaining different OCT images of the target object at different z coordinates at each of the different x and y locations to obtain 3-dimensional image information of the target object at the different locations and at different depths below a surface of the target object, and

wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different images comprises:

averaging a first number of consecutive B-scan images among the different OCT images to obtain an averaged B-scan image;

obtaining a normalized OCT image intensity of a position in the averaged B-scan image by dividing a signal intensity of the position in the averaged B-scan image by a signal intensity at a surface of the target object;

calculating a gradient value of the normalized OCT image intensity in the signal path length direction by subtracting a normalized OCT image intensity in a next depth to the normalized OCT image intensity; and

obtaining the derivative with respect to the signal path length by dividing the gradient value of the normalized OCT image intensity by double actual distance of one pixel.

31. The method of claim 30 , wherein processing the derivative to extract improved image information of the target object comprises:

iteratively calculating derivatives with respect to the signal path length through all positions of the averaged B-scan image; and

reconstructing an OCT slope image having improved image information of the target object from the derivatives with respect to the signal path length through all positions of the averaged B-scan image.

32. The method of claim 30 , wherein processing the different OCT images to obtain a derivative with respect to the signal path length of image information of the different OCT images comprises:

selecting a B-scan image among the different OCT images of the target object under different reference path lengths at different locations shifted in position represented by x and y coordinates;

removing noise in the selected B-scan image to obtain a denoised B-scan image;

obtaining a normalized OCT image intensity by dividing a signal intensity of the denoised B-scan image at each position represented by x and y coordinates by a signal intensity at a surface of the target object;

selecting an A-scan signal of a point at the denoised B-scan image with normalized OCT image intensity;

dividing the signal path length into a plurality of smaller segments;

selecting data of the A-scan signal in the signal depth direction at a segment containing a depth z;

calculating the derivative of the A-scan signal in the segment with the selected data at the segment containing the depth z; and

calculating iteratively derivatives of the A-scan signal through all segments in the signal path.

33. The method of 32 , wherein removing noise in the selected B-scan image to obtain the denoised B-scan image comprises:

removing noise in the selected B-scan image by a Gaussian filter to obtain the denoised B-scan image.

34. The method of claim 30 , comprising:

using a broadband light source to produce light that is used to obtain the different OCT images of the target object.