Photoacoustic vector tomography for deep hemodynamic imaging

TL;DR

This paper introduces photoacoustic vector tomography (PAVT), a novel imaging technique that enables non-invasive, deep blood flow visualization and vector mapping beyond the optical diffusion limit, with potential biomedical applications.

Contribution

PAVT combines optical contrast with photoacoustic imaging to achieve deep, real-time blood flow and direction mapping, surpassing previous optical imaging depth limitations.

Findings

PAVT images blood flow at depths over five millimeters.

It provides pixel-wise flow velocity and direction quantification.

Demonstrated in vivo human deep blood vessel imaging.

Abstract

Non-invasive imaging of deep blood vessels for mapping hemodynamics remains an open quest in biomedical optical imaging. Although pure optical imaging techniques offer rich optical contrast of blood and have been reported to measure blood flow, they are generally limited to surface imaging within the optical diffusion limit of about one millimeter. Herein, we present photoacoustic vector tomography (PAVT), breaking through the optical diffusion limit to image deep blood flow with speed and direction quantification. PAVT synergizes the spatial heterogeneity of blood and the photoacoustic contrast; it compiles successive single-shot, wide-field photoacoustic images to directly visualize the frame-to-frame propagation of the blood with pixel-wise flow velocity estimation. We demonstrated in vivo that PAVT allows hemodynamic quantification of deep blood vessels at five times the optical diffusion limit (more than five millimeters), leading to vector mapping of blood flow in humans. By offering the capability for deep hemodynamic imaging with optical contrast, PAVT may become a powerful tool for monitoring and diagnosing vascular diseases and mapping circulatory system function.