Holographic laser Doppler imaging of microvascular blood flow

TL;DR

This paper introduces a laser Doppler holographic imaging technique for non-invasive, high-resolution mapping of microvascular blood flow in biological tissues, using frequency-selective imaging and optical fluctuation analysis.

Contribution

It presents a novel holographic method combining narrowband filtering and Doppler analysis for detailed microvascular blood flow imaging without exogenous markers.

Findings

Achieved quadratic mean velocity measurement from 0.1 to 10 mm/s.

Demonstrated spatial resolution of about 10 micrometers.

Successfully imaged blood perfusion in rodent cortex and retina.

Abstract

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency shifted reference beam, permits frequency selective imaging in the radiofrequency range. These Doppler images are acquired with an off axis Mach Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse method analysis of local first order optical fluctuation spectra at low radiofrequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1 to 10 millimeters per second range in vitro and imaging of superficial blood perfusion with a spatial resolution of about 10 micrometers in rodent models of cortical and retinal blood flow.