# Super-resolution photoacoustic imaging via flow induced absorption fluctuations

## TL;DR

This paper introduces a novel super-resolution photoacoustic imaging method that leverages flow-induced absorption fluctuations, surpassing traditional acoustic resolution limits and enabling detailed imaging of micro-vessels without contrast agents.

## Contribution

The authors adapt super-resolution optical fluctuation imaging (SOFI) techniques to photoacoustic imaging, generalizing the mathematical framework for complex signals to achieve super-resolution.

## Key findings

- Achieved super-resolved images free from oscillations caused by band-limited detection.
- Demonstrated resolution enhancement using naturally fluctuating red blood cells.
- Applicable to conventional photoacoustic systems without additional hardware.

## Abstract

In deep tissue photoacoustic imaging the spatial resolution is inherently limited by the acoustic wavelength. We present an approach for surpassing the acoustic diffraction limit by exploiting temporal fluctuations in the sample absorption distribution, such as those induced by flowing particles. In addition to enhanced resolution, our approach inherently provides background reduction, and can be implemented with any conventional photoacoustic imaging system. The considerable resolution increase is made possible by adapting notions from super-resolution optical fluctuations imaging (SOFI) developed for blinking fluorescent molecules, to flowing acoustic emitters. By generalizing SOFI mathematical analysis to complex valued signals, we demonstrate super-resolved photoacoustic images that are free from oscillations caused by band-limited detection. The presented technique holds potential for contrast-agent free micro-vessels imaging, as red blood cells provide a strong endogenous source of naturally fluctuating absorption.