Correlation of the derivative as a robust estimator of scatterer size in optical coherence tomography (OCT) [Invited]

Abstract

The size-dependent spectral variations, predicted by Mie theory, have already been considered as a contrast enhancement mechanism in optical coherence tomography. In this work, a new spectroscopic metric, the bandwidth of the correlation of the derivative, was developed for estimating scatterer size which is more robust and accurate compared to existing methods. Its feasibility was demonstrated using phantoms containing polystyrene microspheres as well as images of normal and cancerous human colon. The results are very promising, suggesting that the proposed metric could be utilized for measuring nuclear size distribution, a diagnostically valuable marker, in human tissues.

Extracting morphometric information from rat sciatic nerve using optical coherence tomography

“…24, and then again with additional signal processing steps in Ref. 21. This technique uses Mie theory to generate spectra for spherical scatterers before taking the derivative and then the autocorrelation to produce the CoD.…”

“…The CoD technique estimated the diameters of microsphere samples of 3.8-, 5.33-, and 8.49-μm diameter as 2.6 þ ∕ − 0.7, 2.8 þ ∕ − 0.5, and 4.5 þ ∕ − 0.3 μm (mean þ ∕ − 1 standard deviation), respectively, which indicates poor diameter estimate accuracy for all microsphere diameters, Table 2. All estimates corresponded to a scanning window axial size of 4 pixels, selected to minimize the standard deviation, whereas the smallest window axial size used in the original study was 5 pixels, 21 Figs. 8(a)-8(c).…”

“…On the other hand, quantitative OCT techniques, such as the depth-resolved analysis of optical properties 18 and statistical analysis of spectra, 19,20 provide quantified values for nerve tissue morphometry but have not been validated. Other quantitative OCT techniques, such as the analysis of Mie scatter spectra 21 and optical scattering properties, 22 have been used to classify tissue, but have not yet been applied to peripheral nerves. There is, therefore, a need to evaluate and validate the performance of OCT techniques in imaging peripheral nerves, which builds on preliminary work in Ref.…”

“…We compare our results with the histological analysis performed on light-microscopy images, a step that is absent in the original reporting of the OCT techniques. [18][19][20][21]24 When replicating each technique, parameters were selected using unbiased methods, or otherwise noted as biased, to ensure fair comparison and practical application. We demonstrate applications of the two scatterer size estimation techniques using them to evaluate the combined thickness of epineurium and perineurium tissue, and to differentiate adipose tissue from neural tissues.…”

Introduction to the feature issue on the 25 year anniversary of optical coherence tomography

“…As discussed in the following cited Invited Review and Invited Research articles in this issue, remarkable strides have since been made in OCT technology encompassing novel light sources [2], imaging system architectures [3,4], and sample/patient interface technologies including endoscopic [5], catheter-based [6], intra-operative [7], adaptive-optic [8][9][10], computational [11] and microscope-based [12] implementations. Functional extensions of OCT have been developed featuring polarization-based [13], Doppler [14], elastographic [15], tractographic [16], spectroscopic [17,18] multi-modal [19] and angiographic [8,20,21] contrast, the latter of which has taken on particular current excitement and topically comprises the plurality of articles published in this Issue. Clinical applications of OCT have been developed in dozens of medical specialties, led by its most mature applications in ophthalmology and cardiology, where OCT has become a clinical standard of care and is now performed in an estimated 30 million OCT imaging procedures per year [22].…”