Dual-modal Photoacoustic and Fluorescence Endomicroscopy through a Multimode Fibre

Abstract

Needle biopsy is a reliable approach for the examination of the tumour with minimal tissue damage. However, there is a high rate of inadequate tissue sampling as tissue samples may be taken from non-diagnostic or nonrepresentative regions. In this thesis, a dual-modal photoacoustic (PA) and fluorescence endomicroscopy probe was fabricated for guiding the needle to appropriate sites to improve the accuracy of biopsy. A multimode fibre (MMF) was used for transmitting the laser and collecting the excited fluorescence light, whilst a fibre-optic ultrasound sensor based on a plano-concave microresonator was combined for detecting optically generated ultrasound. The probe had a small footprint of 300 μm ⇥ 140 μm, and thus it can be placed in the cannula of a needle. Microscopy imaging with both PA and fluorescence modalities relied on wavefront shaping to raster-scan a focused laser beam through the MMF. A digital micromirror device (DMD) was used for modulating the incident light fields, and it enabled the high-speed acquisition of images. A real-valued intensity transmission matrix (RVITM) algorithm was developed for the MMF calibration, which was suited for PA imaging as it benefited from high focusing performance and efficient utilisation of light energy. High-resolution imaging was demonstrated with both phantoms and mouse blood samples. With dual-modal, high-resolution, and high-speed imaging, this endomicroscopy probe is promising to provide preliminary examination of the tissue in front of the needle tip to guide the sampling in needle biopsy and thus improve the accuracy of the tumour diagnosis.

Date of Award	3 May 2022
Original language	English
Awarding Institution	King's College London
Supervisor	Tom Vercauteren (Supervisor) & Wenfeng Xia (Supervisor)