High-speed widefield photoacoustic microscopy of small-animal hemodynamics.

Bangxin Lan,Yang Li,Wei Liu,Qifa Zhou,Junjie Yao,Ya-Chao Wang,Ulrike Hoffmann,Wei Yang,Song Xu,Junhui Shi,Jun Zou,Huaxin Sheng

doi:10.1364/boe.9.004689

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 motor-scanner-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.

Highlights

Optical-resolution photoacoustic microscopy (OR-PAM) has been playing an increasingly important role in small animal studies [1], taking advantage of its rich optical absorption contrast [2], high spatial resolution [3], and intrinsic volumetric imaging capability [4]
Using the hexagon scanning mirror steered by a water-immersible high-precision DC motor, HM-OR-PAM has achieved a maximum B-scan rate of 900 Hz over a 12-mm scanning range, while maintaining confocal alignment of the optical and acoustic beams
As the diameters of microvessels in small animal models generally fall in the range of 10–100 μm [33], HM-OR-PAM can still meet the need of high-resolution imaging

Summary

Introduction

Optical-resolution photoacoustic microscopy (OR-PAM) has been playing an increasingly important role in small animal studies [1], taking advantage of its rich optical absorption contrast [2], high spatial resolution [3], and intrinsic volumetric imaging capability [4]. A novel scanning method is highly desired for OR-PAM that can simultaneously achieve (1) a high imaging speed for dynamic imaging, (2) a large scanning range for a wide field of view, and (3) confocal scanning of optical and acoustic beams for high detection sensitivity. Using the hexagon scanning mirror steered by a water-immersible high-precision DC motor, HM-OR-PAM has achieved a maximum B-scan rate of 900 Hz over a 12-mm scanning range, while maintaining confocal alignment of the optical and acoustic beams. To demonstrate the dynamic imaging of biological activities in vivo, we monitored the epinephrine-induced vasoconstriction in the entire mouse ear, and the blood reperfusion after ischemic stroke in the entire mouse cortex These results have collectively demonstrated the high-speed widefield imaging capability of HM-OR-PAM for preclinical applications

The HM-OR-PAM system

Spatial resolutions

Fast-scanning step size

Validating the system performance on phantoms and in vivo

Findings

Conclusion and discussion