Quantitative methods for obtaining tissue characteristics from optical coherence tomography images

Abstract

A method and apparatus for determining properties of a tissue or tissues imaged by optical coherence tomography (OCT). In one embodiment the backscatter and attenuation of the OCT optical beam is measured and based on these measurements and indicium such as color is assigned for each portion of the image corresponding to the specific value of the backscatter and attenuation for that portion. The image is then displayed with the indicia and a user can then determine the tissue characteristics. In an alternative embodiment the tissue characteristics is classified automatically by a program given the combination of backscatter and attenuation values.

1 . A processor-implemented method for identifying tissue components in situ comprising the steps of:
 a. collecting an OCT dataset of a tissue sample in situ using a probe;   b. measuring an attenuation value and a backscattering value at a point in the tissue sample; and   c. determining a tissue characteristic at a location in the tissue sample corresponding to an image location in an OCT image formed from the OCT dataset in response to the measured attenuation value and backscattering value.   
     
     
         2 . The method of  claim 1  further comprising mapping a pair of coordinates in backscatter-attenuation space to an indicium of the value of the pair of coordinates in the backscatter-attenuation space. 
     
     
         3 . The method of  claim 2  wherein the indicium is a color. 
     
     
         4 . The method of  claim 2  further comprising displaying the indicium corresponding to the measured attenuation and backscatter at the point in the OCT image. 
     
     
         5 . The method of  claim 1  wherein the tissue characteristic is selected from the group consisting of cholesterol, fiber, lipid pool, fibrofatty, calcification, red thrombus, white thrombus, foam cells, and proteoglycan. 
     
     
         6 . The method of  claim 1  wherein the indicium is selected from the group consisting of an over-lay, a colormap, a texture map, and text. 
     
     
         7 . The method of  claim 1  further comprising the step of classifying tissue type using a property selected from the group consisting of backscattering, attenuation, edge sharpness and texture measurements. 
     
     
         8 . The method of  claim 1  further comprising the step of correcting a focusing effect to improve tissue type classification. 
     
     
         9 . The method of  claim 1  further comprising the step of applying angular intensity correction to account for an attenuation effect. 
     
     
         10 . The method of  claim 9  wherein the attenuation effect is blood related. 
     
     
         11 . The method of  claim 1  further comprising the step of determining a tissue characteristic using a technique selected from the group consisting of boundary detection, lumen location, and OCT location depth determination. 
     
     
         12 . A system for identifying tissue components in situ comprising:
 a. an OCT subsystem for taking an OCT image of a tissue in situ;   b. a processor in communication with the OCT subsystem for measuring the attenuation and backscatter at a point in the OCT image and determining a tissue characteristic of the tissue at a location in the tissue corresponding to the point in the OCT image in response to the measured attenuation and backscatter; and   c. a display for displaying the OCT image and an indicium corresponding to the measured attenuation and backscatter at the point in the OCT image.   
     
     
         13 . The system of  claim 12  wherein the tissue characteristic is selected from the group consisting of cholesterol, fiber, fibrous, lipid pool, lipid, fibrofatty, calcium nodule, calcium plate, calcium speckled, thrombus, foam cells, and proteoglycan. 
     
     
         14 . An optical coherence tomography system for identifying tissue characteristics of a sample, the computer system comprising:
 a detector configured to receive an optical interference signal generated from scanning a sample and converting the optical interference signal to an electrical signal;   an electronic memory device and   an electronic processor in communication with the memory device and the detector, wherein the memory device comprises instructions that when executed by the processor cause the processor to:
 analyze the electrical signal and generate a plurality of datasets corresponding to the sample, wherein one of the plurality of datasets comprises backscattering data; 
 compare the backscattering data to a first threshold, the backscattering data mapping to a first location in the sample; and 
 if the backscattering data exceeds the first threshold, characterize the first location in the sample as having a first tissue characteristic. 
   
     
     
         15 . The system of  claim 14  wherein the first tissue characteristic is selected from the group consisting of cholesterol, fiber, fibrous, lipid pool, lipid, fibrofatty, calcium nodule, calcium plate, calcium speckled, thrombus, foam cells, and proteoglycan. 
     
     
         16 . The system of  claim 14  wherein the processor is further caused to generate an OCT image of the sample such that the first tissue characteristic is identified and displayed relative to the first location. 
     
     
         17 . The system of  claim 14  wherein one of the plurality of datasets comprises OCT scan data, attenuation data, edge sharpness data, texture parameters, and interferometric data.