System and method for determining volume-related parameters of ocular and other biological tissues

• US 9,050,025 B2
• Filed: 06/18/2009
• Issued: 06/09/2015
• Est. Priority Date: 06/18/2008
• Status: Active Grant

• Current Assignee: Eyelab Group, LLC
• Original Assignee: Eyelab Group, LLC
• Inventors: Dilworth, David S., Cohan, Bruce E., Flanders, Zvi, Peshkin, Hannah R.
• Primary Examiner(s): EVOY, NICHOLAS LANE
• Application Number:
  US12/487,143
• Publication Number:
  US 20100160789A1
• Time in Patent Office: 2,182 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: A61B 3/0025 characterised by electronic signal processing, e.g. eye models
• CPC Class Codes: A61B 3/1005 for measuring distances inside the eye, e.g. thickness of the cornea A61B3/11 takes precedence
• CPC Class Codes: A61B 3/12 for looking at the eye fundus, e.g. ophthalmoscopes A61B3/13 takes precedence
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/1072 measuring distances on the body, e.g. measuring length, height or thickness A61B5/1076 takes precedence
• CPC Class Codes: A61B 5/1079 using optical or photographic means
• CPC Class Codes: A61B 5/7235 Details of waveform analysis A61B5/349 takes precedence

Abstract

A system and method for determining volume-related parameters of a biological tissue, such as ocular tissue, include a light source for projecting light towards the biological tissue, a receiver for receiving light reflected from the biological tissue at two spectral wavelengths, and an image acquisition system in communication with the receiver for forming an image from the reflected light at each wavelength. A processor applies a mathematical model to the image which compares the absorption of light by the biological tissue at a selected image point at each of the two spectral wavelengths to determine the volume-related parameters, such as the relative thickness and material properties, of the biological tissue at that location.

Claims

1. A system for determining a relative thickness of optic disc tissue, comprising:

a light source configured to project broad spectrum light towards the optic disc tissue;

a receiver configured to receive light reflected from the optic disc tissue at at least two spectral wavelengths;

a digitizer in communication with the receiver configured to form a first image from the reflected light at each wavelength at a first time, and configured to form a second image from the reflected light at each wavelength at a second time; and

a processor configured to

determine a normalization point in each of the first and second images, compute a difference in the absorption of light by the optic disc tissue at selected image points in each image at each of the two spectral wavelengths to determine a thickness at each selected image point,

determine relative thicknesses of the optic disc tissue of each image by compassing the thickness at each selected image point to the normalization point,

compute an average of the relative thickness for each image to obtain an average thickness for each image,

select one average thickness from the images to be a reference average thickness, and

compute the difference between the average thickness and the reference average thickness for the first and second images to determine a relative thickness of the optic disc tissue over time.

2. The system according to claim 1, wherein the processor utilizes a mathematical model that assumes that the absorption of light by the optic disc tissue is an exponential function of the thickness of the optic disc tissue.

3. The system according to claim 1, wherein the selected image point is a single pixel in the image.

4. The system according to claim 1, further comprising a database for storing images and related data.

5. The system according to claim 1, further comprising a display for displaying the images.

16. The system according to claim 1, wherein the processor is configured to compute a ratio of the absorption of light by the optic disc tissue at each selected image point at each of the two spectral wavelengths to determine a material property of the optic disc tissue at each selected image point.

6. A method for determining a relative thickness of optic disc tissue, comprising:

illuminating the optic disc tissue with broad spectrum light with a light source;

receiving light at a receiver reflected from the optic disc tissue at at least two spectral wavelengths;

forming a first image from the reflected light at each wavelength with a digitizer at a first time, and forming a second image from the reflected light at each wavelength with the digitizer at a second time; and

processing the image with a processor, wherein processing includes;

determining a normalization point in each of the first and second images;

computing a difference in the absorption of light by the optic disc tissue at selected image points in each image at each of the two spectral wavelengths to determine a thickness at each selected image point,

determining relative thicknesses of the optic disc tissue of each image by comparing the thickness at each selected image point to the normalization point;

computing an average of the relative thicknesses for each image to obtain an average thickness for each image;

selecting one average thickness from the images to be a reference average thickness; and

computing the difference between the average thickness and the reference average thickness for the first and second images to determine a relative thickness of the optic disc tissue over time.

7. The method according to claim 6, wherein determining the relative thicknesses includes relating the absorption of light by the optic disc tissue to the thickness of the optic disc tissue by an exponential function.

8. The method according to claim 6, wherein each selected image point is a single pixel in the image.

9. The method according to claim 6, further comprising storing images and related data.

10. The method according to claim 6, further comprising generating a grayscale image representing the tissue thickness from the formed image.

11. The method according to claim 10, further comprising generating a three-dimensional rendering combining the formed image and the grayscale image.

12. The method according to claim 6, further comprising identifying fiducial points of interest on the image, finding line segments between distinct features of the image that span the points of interest and the percentage along the line segment of the points of interest, and applying the line segments and percentages to another image to allow location of the points of interest on the other image for comparing the volume-related parameters between the images.

13. The method according to claim 6, further comprising displaying the image.

14. The method according to claim 6, further comprising using the determined relative thicknesses for assessing a glaucoma condition of an optic disc.

15. The method according to claim 12, wherein the fiducial points of interest are identified on an outer edge of an optic disc.

17. The method of claim 6, further comprising computing a ratio of the absorption of light by the optic disc tissue at each selected image point at each of the two spectral wavelengths to determine a material property of the optic disc tissue at each selected image point.