Photoacoustic endoscopy (PAE) allows close visualisation of internal tissues that are challenging to be assessed from outside. It usually employs optical fibres to deliver light to optically excite ultrasound from internal tissues and detect these ultrasound signals with a detector integrated with the fibre. Conventional designs of PAE usually comprise piezoelectric transducers for photoacoustic signals detection, however, due to their opaque nature, these transducers are required to be laterally offset, leading to reduced acoustic sensitivity and increased footprint dimensions. In this work, we fabricated a miniaturized transparent ultrasound sensor using a transparent polyvinylidene fluoride (PVDF) thin film coated with indium tin oxide (ITO) electrodes for PAE. The PVDF-ITO thin film was coated at the tip of a brass tube that had an outer diameter of 2 mm and an inner diameter of 1 mm. A multimode optical fibre was inserted into the brass tube to deliver nano-second-pulsed laser through the PVDF-ITO sensor for photoacoustic signals excitation. The sensor showed an optical transmission rate of ~ 65% to 75% in the wavelength range of 450 to 700 nm, and the photoacoustic signals generated from a carbon fibre had a centre frequency of 15 MHz and a -10 dB bandwidth of 30 MHz. Raster scanning of a focused laser beam on a carbon fibre phantom was performed to obtain optical-resolution photoacoustic endomicroscopy images using a high-speed digital micromirror device via wavefront shaping. Further pre-clinical experiments (tissue samples and in vivo) are required to evaluate the potential of the imaging system for guiding minimally invasive procedures.
|Title of host publication
|Proceedings Volume 11960, Photons Plus Ultrasound: Imaging and Sensing 2022
|Number of pages
|Published - 7 Mar 2022