Textural Feature Analysis of Optical Coherence Tomography Phantoms

Mukhit Kulmaganbetov,Nantheera Anantrasirichai,Ryan J Bevan,Alin Achim,Julie Albon,Irina Erchova,Nick White,James E Morgan

doi:10.3390/electronics11040669

Abstract

Optical coherence tomography (OCT) is an imaging technique based on interferometry of backscattered lights from materials and biological samples. For the quantitative evaluation of an OCT system, artificial optical samples or phantoms are commonly used. They mimic the structure of biological tissues and can provide a quality standard for comparison within and across devices. Phantoms contain medium matrix and scattering particles within the dimension range of target biological structures such as the retina. The aim was to determine if changes in speckle derived optical texture could be employed to classify the OCT phantoms based on their structural composition. Four groups of phantom types were prepared and imaged. These comprise different concentrations of a medium matrix (gelatin solution), different sized polystyrene beads (PBs), the volume of PBs and different refractive indices of scatterers (PBs and SiO2). Texture analysis was applied to detect subtle optical differences in OCT image intensity, surface coarseness and brightness of regions of interest. A semi-automated classifier based on principal component analysis (PCA) and support vector machine (SVM) was applied to discriminate the various texture models. The classifier detected correctly different phantom textures from 82% to 100%, demonstrating that analysis of the texture of OCT images can be potentially used to discriminate biological structure based on subtle changes in light scattering.

Highlights

Optical coherence tomography (OCT) is in routine use for the assessment of morphological and physiological characteristics of biological structures such as the retina at micron scales
Available OCT devices use low coherence light sources typically centered in the wavelength range around 840 nm or 1040 nm; their axial resolution is determined by the full width at half maximum (FWHM) of the light source and not by the aberrations of the optic system [2]
For the purpose of classification, we developed 4 phantom groups based on differences in the concentration of gelatin, particle size, particle concentration and particle refractive index

Summary

Introduction

Optical coherence tomography (OCT) is in routine use for the assessment of morphological and physiological characteristics of biological structures such as the retina at micron scales. Available OCT devices use low coherence light sources typically centered in the wavelength range around 840 nm or 1040 nm; their axial resolution is determined by the full width at half maximum (FWHM) of the light source and not by the aberrations of the optic system [2]. Fourier-domain OCT measures the phase of the Fourier transform of the spectral interference between the backscattered lights from both arms of a device [4]. This phase is an estimate of structural information about the sample refractive index (RI) within the implicit coherence gating enforced by the spectral bandwidth of the light source [5]. The measurement of retinal layers is based on the segmentation and texture analysis of multi-cellular structures along each axial intensity line

Methods

Results

Conclusion