High-speed widefield photoacoustic microscopy of small-animal hemodynamics

Abstract

Optical-resolution photoacoustic microscopy (OR-PAM) has become a popular tool in small-animal hemodynamic studies. However, previous OR-PAM techniques variously lacked a high imaging speed and/or a large field of view, impeding the study of highly dynamic physiologic and pathophysiologic processes over a large region of interest. Here we report a high-speed OR-PAM system with an ultra-wide field of view, enabled by an innovative water-immersible hexagon-mirror scanner. By driving the hexagon-mirror scanner with a high-precision DC motor, the new OR-PAM has achieved a cross-sectional frame rate of 900 Hz over a 12-mm scanning range, which is 3900 times faster than our previous motorscanner-based system and 10 times faster than the MEMS-scanner-based system. Using this hexagon-scanner-based OR-PAM system, we have imaged epinephrine-induced vasoconstriction in the whole mouse ear and vascular reperfusion after ischemic stroke in the mouse cortex in vivo, with a high spatial resolution and high volumetric imaging speed. We expect that the hexagon-scanner-based OR-PAM system will become a powerful tool for small animal imaging where the hemodynamic responses over a large field of view are of interest.

A Review of Endogenous and Exogenous Contrast Agents Used in Photoacoustic Tomography with Different Sensing Configurations

“…A customized ring-shaped UT (i.e., a hollow structure at the center), Figure 10 c, can be incorporated into a reflection-mode PAM system [ 129 ]. The laser beam is focused on the sample through the ring-shaped UT, and the backward propagating PA waves would be detected by the same ring-shaped UT.…”

Multifocal structured illumination optoacoustic microscopy

“…Water-immersed scanning optical mirrors have similarly enabled acoustic beam deflection and effective scanning of the sensitivity field of a focused ultrasound detector. It is, for instance, possible to achieve very fast B-scan rates across FOVs of several millimetres by means of a one-dimensional (1D) galvo mirror immersed in non-conducting liquid hydrofluoroether 22 or an immersible hexagon-mirror scanner driven by a DC motor 23 . Alternatively, small optical sensors with broad angular acoustic sensitivity have been suggested in which a larger FOV can be achieved solely by scanning the optical beam 24 .…”

Optical-Resolution Photoacoustic Microscopy Using Transparent Ultrasound Transducer

“…Optical-resolution photoacoustic microscopy (OR-PAM) has recently gained significant attention from the biomedical-imaging community as it provides labelfree optical contrast from physiologically relevant tissue chromophores that are located a few millimeters deep, with subcellular spatial resolution [1][2][3][4][5]. In OR-PAM, a tightly focused laser pulse illuminates the tissue and generates wideband acoustic waves from light-absorbing chromophores that are then detected by an acoustic transducer.…”