# MECOPE: Multifocal excitation compressive-sensing photoacoustic endomicroscopy through a multimode fibre

## TL;DR

This paper introduces a new photoacoustic endomicroscopy system using multimode fibers that improves imaging speed and quality for potential use in minimally invasive medical procedures.

## Contribution

The novel system combines multifocal excitation and compressive sensing to enhance frame rate and image quality in photoacoustic endomicroscopy.

## Key findings

- The system achieved a 5x improvement in frame rate, reaching 11.5 frames per second.
- Image quality was comparable to traditional raster-scan methods.
- Validation was performed using simulations and experiments with carbon fiber phantoms and red blood cells.

## Abstract

Photoacoustic endoscopy has gained intensive research interest in recent years, particularly for guiding minimally invasive procedures in several clinical disciplines including oncology, cardiology and fetal medicine. Multimode fibres hold the potential to revolutionise medical endoscopy with ultrathin size and micrometre-level resolution. Compared to conventional endomicroscopes based on multi-core fibre bundles, multimode fibres-based endoscopes offer significantly higher spatial resolution, smaller diameters, and lower costs. However, current implementations of multimode fibre imaging, whether using raster-scan or speckle compressive sensing imaging, are hindered by limitations in frame rate or signal-to-noise ratio. In this work, we developed a multifocal excitation compressive-sensing photoacoustic endomicroscopy system that combines wavefront shaping-based light focusing with compressive sensing to achieve high imaging speed without compromising image quality. The method was validated through numerical simulations and experiments with carbon fibre phantoms and red blood cells ex vivo. Our results demonstrated comparable image quality to raster-scan-based imaging, while improving the frame rate by a factor of 5, reaching 11.5 frames per second. With further enhancements in focusing performance and the use of a higher repetition rate laser, this method shows promise for achieving real-time, high-resolution endomicroscopy through ultrathin probes, making it a valuable tool for guiding minimally invasive procedures.