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 radio frequency 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 radio frequencies, from 0Hz to 100kHz. 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 0.1-10mm/s 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.
Highlights
We report on quantitative fluid flow assessment in vitro and in vivo from holographic interferometry, which enables wide-field imaging of a Doppler-shifted radiation with an array detector
We demonstrated that holographic laser Doppler imaging has the potential to enable quantitative assessment of hemodynamic parameters
Cerebral and retinal blood flow was mapped in the superficial microvasculature of rodents
Summary
The role of the microcirculation is increasingly being recognized in the pathophysiology of cardiovascular diseases; eg. hypertension [1,2,3] and diabetes [4,5,6]. Assessing retinal blood flow can be potentially useful for understanding diabetic retinopathies [7], and study the relationships between vascularization and glaucoma [8,9,10,11,12]. Prevalent optical techniques to monitor microvascular blood flow in clinical studies are laser Doppler probes and spatial speckle contrast imaging. The former is characterized by its high temporal resolution and the latter enables wide-field imaging of superficial microvascular networks. Wide-field optical imaging techniques using laser light and sensor arrays to probe local dynamics with potentially high spatial and temporal resolution are attracting attention for the measurement of blood flow [19]
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