Phase-Resolved Optical Coherence Elastography: An Insight into Tissue Displacement Estimation.

Robust methods to compute tissue displacements in optical coherence elastography (OCE) data are paramount, as they play a significant role in the accuracy of tissue elastic properties estimation. In this study, the accuracy of different phase estimators was evaluated on simulated OCE data, where the displacements can be accurately set, and on real data. Displacement (∆d) estimates were computed from (i) the original interferogram data (Δφori) and two phase-invariant mathematical manipulations of the interferogram: (ii) its first-order derivative (Δφd) and (iii) its integral (Δφint). We observed a dependence of the phase difference estimation accuracy on the initial depth location of the scatterer and the magnitude of the tissue displacement. However, by combining the three phase-difference estimates (Δdav), the error in phase difference estimation could be minimized. By using Δdav, the median root-mean-square error associated with displacement prediction in simulated OCE data was reduced by 85% and 70% in data with and without noise, respectively, in relation to the traditional estimate. Furthermore, a modest improvement in the minimum detectable displacement in real OCE data was also observed, particularly in data with low signal-to-noise ratios. The feasibility of using Δdav to estimate agarose phantoms' Young's modulus is illustrated.

A new optics-based gastroesophageal reflux probe.

This work was carried out with the purpose of developing a new method of gastroesophageal reflux (GOR) detection. It is based on the emission of a light beam to the inferior part of the oesophagus and on the detection and analysis of the corresponding reflected light intensity. The optical properties of the oesophageal lumen are then used to identify the GOR episodes, solving, in this way, the existing drawback of using pH probes that fail in the cases where GOR episodes are neutral or short duration acid. The necessary instrumentation for the application of this new technique, including the probe itself and its associated optics, was developed. The result is a low-cost portable instrument, based on the Microchip microcontroller PIC16C77, with enough flexibility to be used in other biomedical applications. This new simple apparatus only needs an adequate light source - diode laser - and an adequate photosensor - photodiode - to make the interface to the probe that guides the light to and from oesophagus. Our results show the capability of this new technique to make the identification of GOR episodes.