# Super-resolution functional photoacoustic microscopy via label-free cell tracking

## TL;DR

A new imaging technique called SR-fPAM allows detailed, label-free tracking of blood cells and oxygen levels in microvascular networks in living mice.

## Contribution

SR-fPAM introduces a novel method for high-resolution, functional imaging of microvascular oxygen dynamics and blood flow at the single-cell level.

## Key findings

- SR-fPAM reconstructs 3D microvascular architecture comparable to two-photon microscopy.
- The method provides quantitative measurements of red blood cell flow and oxygenation in live mice.
- SR-fPAM reveals oxygen redistribution in microvascular networks after a single-vessel stroke.

## Abstract

Microvascular function and oxygen metabolism are central to tissue and organ health. However, label-free methods for imaging oxygen dynamics in three-dimensional (3D) microvascular networks at the level of single red blood cells (RBCs)—the fundamental units of oxygen transport in vivo—remain lacking. Here, we introduce super-resolution functional photoacoustic microscopy (SR-fPAM), which spatiotemporally tracks RBC movements under dual-wavelength excitation. SR-fPAM reconstructs super-resolved 3D microvascular architecture comparable to two-photon microscopy while providing quantitative measurements of RBC flow and oxygenation. In live mice, SR-fPAM revealed redistribution of oxygen and hemodynamics across 3D microvascular networks following a single-vessel stroke. These findings establish SR-fPAM as an enabling tool that bridges a critical gap in oxygen-metabolism imaging and opens new avenues for studying microvascular health and disease with unprecedented functional insights.

This work introduces super-resolution functional photoacoustic microscopy (SR-fPAM), which enables label-free three-dimensional imaging of microvascular structure, blood oxygenation, and blood flow at single-cell spatial resolution.