Advanced systems and methods for collecting accurate data in optical coherence tomography

Abstract

Optical coherence tomography (OCT) has recently emerged as a valuable technique in biomedical research and medical diagnostics. OCT based instruments allow acquisi- tion of high-resolution information about the internal structure of translucent organs and tissues without damaging the object. However, unaccounted object movements reduce the quality of acquired data, particularly in functional imaging and in OCT modalities that rely on continuous monitoring. Therefore there is a need for methods that allow mitigating the negative effects of the object movements on the data quality. In this thesis we present several methods and devices that allow improving the ac- curacy of collected data. First we introduce a novel frequency multiplexing method for OCT, which enables simultaneous measurements using several frequency-encoded channels. By doing so, several parameters are measured in the same time, reducing the time to acquire the data and making the technology less sensitive to object movements. We employed the method to extend the functionality of several OCT modalities. We have applied the multiplexer to enable simultaneous en face time domain OCT imag- ing at different depths. We have demonstrated a polarisation sensitive OCT set-up where different multiplexer channels are employed to perform polarisation sensitive measurements. Furthermore, we have demonstrated how the multiplexer can be applied to extend the sensitivity range in swept source based OCT systems. The experiments presented in this thesis illustrate the flexibility of our new multiplexing method, which has proven useful not only for increasing the accuracy of collected data, but as well for increasing the efficiency in using the light from the object. Alternatively, we have investigated tracking as a way to improve the quality of the OCT data acquired from the moving targets. We have demonstrated a closed-loop tracking based set-up that uses low coherence interferometry to continuously monitor the cardiac dynamics of a Drosophila melanogaster embryo.