High-speed and high-SNR photoacoustic microscopy based on a galvanometer mirror in non-conducting liquid

Abstract

Optical-resolution photoacoustic microscopy (OR-PAM), a promising microscopic imaging technique with high ultrasound resolution and superior optical sensitivity, can provide anatomical, functional, and molecular information at scales ranging from the microvasculature to single red blood cells. In particular, real-time OR-PAM imaging with a high signal-to-noise ratio (SNR) is a prerequisite for widespread use in preclinical and clinical applications. Although several technical approaches have been pursued to simultaneously improve the imaging speed and SNR of OR-PAM, they are bulky, complex, not sensitive, and/or not actually real-time. In this paper, we demonstrate a simple and novel OR-PAM technique which is based on a typical galvanometer immersed in non-conducting liquid. Using an opto-ultrasound combiner, this OR-PAM system achieves a high SNR and fast imaging speed. It takes only 2 seconds to acquire a volumetric image with a wide field of view (FOV) of 4 × 8 mm2 along the X and Y axes, respectively. The measured lateral and axial resolutions are 6.0 and 37.7 μm, respectively. Finally, as a demonstration of the system’s capability, we successfully imaged the microvasculature in a mouse ear in vivo. Our new method will contribute substantially to the popularization and commercialization of OR-PAM in various preclinical and clinical applications.

Feasibility Study of Precise Balloon Catheter Tracking and Visualization with Fast Photoacoustic Microscopy

“…Finally, two or three-dimensional images can be obtained via reconstruction algorithms. Thanks to less scattering of ultrasound in biological tissue, PAI can achieve deep tissue imaging while maintaining ultrasonic resolution [ 20 , 21 , 22 , 23 , 24 ]. Furthermore, depending on aiming applications, PAI can provide multiscale images from several nanometers to several centimeters selectively by controlling systemic specifications between optical and ultrasonic [ 25 ].…”

Optical-Resolution Photoacoustic Microscopy Using Transparent Ultrasound Transducer

“…Scan speed could be improved by using state-of-the-art scanning methods, such as galvo-mirror-based scanning of the optical beam like that employed in conventional OR-PAM systems. This could achieve a scanning speed of 1000 × 1000 steps in 100 s [7]. The SNR could be improved by further investigating novel high-acoustic absorption backing and proper impedance-matching layers.…”

“…The current generation of OR-PAMs reflect the light, instead of the acoustic waves, by sandwiching an aluminium foil in the acoustic-optic combiner. This allows dual axis optic only scanning using a two dimensional galvo mirror to improve the image acquisition speed and generate a wide FOV [7]. The entire imaging head, including the galvo mirror, is submerged in a large volume (70 × 40 × 20 mm 3 ) of a nonconducting liquid coupling medium that rests above the imaged subject.…”

Biodegradable Contrast Agents for Photoacoustic Imaging

“…Photoacoustic imaging (PAI) is considered a promising volumetric imaging technique for biomedical applications based on hybrid contrast mechanism under a light illumination and emitted ultrasound capturing scheme which enables to provide spectroscopic optical contrast and ultrasonic high-resolution. Additionally, PAI can achieve deep tissue imaging (several centimeters) by overcoming the bottleneck of the typical optical penetration depth (theoretically~1 mm) [1][2][3][4][5][6][7][8]. Furthermore, using the intrinsic optical absorption contrast between various components, including hemoglobin, melanoma, collagen and fat, PAI can visualize anatomical information such as vasculature distributions, melanin location, tendons and plaques, as well as physiological information such as the total amount of hemoglobin, oxygen saturation ratio, blood velocity and metabolic ratio [9][10][11].…”