Extracting morphometric information from rat sciatic nerve using optical coherence tomography

TL;DR

This study evaluates three OCT image analysis techniques for extracting morphometric data from rat sciatic nerve, demonstrating their potential and limitations compared to histological measurements.

Contribution

The paper introduces and compares three OCT analysis methods, including a new scanning window for ADRP, to improve morphometric estimations of nerve tissues.

Findings

ADRP with scanning window improved agreement with histology from 2/10 to 5/10 images.

AR-SE accurately estimated epineurium thickness in 6/10 images.

Both AR-SE and CoD-SE correctly identified larger fascicle but underestimated fiber diameter differences.

Abstract

We apply three optical coherence tomography (OCT) image analysis techniques to extract morphometric information from OCT images obtained on peripheral nerves of rat. The accuracy of each technique is evaluated against histological measurements accurate to +/-1 um. The three OCT techniques are: 1) average depth resolved profile (ADRP); 2) autoregressive spectral estimation (AR-SE); and, 3) correlation of the derivative spectral estimation (CoD-SE). We introduce a scanning window to the ADRP technique which provides transverse resolution, and improves epineurium thickness estimates - with the number of analysed images showing agreement with histology increasing from 2/10 to 5/10 (Kruskal-Wallis test, {\alpha} = 0.05). A new method of estimating epineurium thickness, using the AR-SE technique, showed agreement with histology in 6/10 analysed images (Kruskal-Wallis test, {\alpha} = 0.05). Using a tissue sample in which histology identified two fascicles with an estimated difference in mean fibre diameter of 4 um, the AR-SE and CoD-SE techniques both correctly identified the fascicle with larger fibre diameter distribution but incorrectly estimated the magnitude of this difference as 0.5um. The ability of OCT signal analysis techniques to extract accurate morphometric details from peripheral nerve is promising but restricted in depth by scattering in adipose and neural tissues.