High-speed functional photoacoustic microscopy using a water-immersible two-axis torsion-bending scanner

Abstract

Optical-resolution photoacoustic microscopy (OR-PAM) can provide functional, anatomical, and molecular images at micrometer level resolution with an imaging depth of less than 1 mm in tissue. However, the imaging speed of traditional OR-PAM is often low due to the point-by-point mechanical scanning and cannot capture time-sensitive dynamic information. In this work, we demonstrate a recent effort in improving the imaging speed of OR-PAM, using a newly developed water-immersible two-axis scanner. Driven by water-compatible electromagnetic actuation force, the new scanning mirror employs a novel torsion-bending mechanism to achieve fast 2D scanning. The torsion scanning along the fast-axis works in the resonant model, and the bending scanning along the slow-axis operate at the quasi-static mode. The scanning speed and scanning range along the two axes can be independently adjusted. Steered by the two-axis torsion-bending scanning mirror immersed in water, the focused excitation light and the generated acoustic wave can be confocally aligned over the entire imaging area. Thus, a high imaging speed can be achieved without sacrificing the detection sensitivity. Equipped with the torsion-bending scanner, the high-speed OR-PAM system has achieved a cross-sectional frame rate of 400 Hz, and a volumetric imaging speed of 1 Hz over a field of view of 1.5 × 2.5 mm 2 . We have also demonstrated high-speed OR-PAM of the hemodynamic changes in response to pharmaceutical and physiological challenges in small animal models in vivo. We expect the torsion-bending scanner based OR-PAM will find matched biomedical studies of tissue dynamics.

Fully integrated photoacoustic microscopy and photoplethysmography of human in vivo

“…With the recently developed transparent US transducers, such multimodal sensing and imaging may be easily implemented [37] , [38] . In addition, the PAM-PPG system has the potentials to provide blood oxygen saturation in different sites through multispectral analysis, and each modality has been separately proved for this purpose [39] , [40] , [41] , [42] , [43] , [44] . Likewise, the integrated PAM-PPG system can furnish with both capillary and arterial oxygen saturations by employing multi-wavelength light sources.…”

High-speed optical resolution photoacoustic microscopy with MEMS scanner using a novel and simple distortion correction method

“…In addition, we can refer to previous studies on high-speed PAM systems using high-speed laser PRFs to achieve faster imaging. For example, Chen et al constructed a high-speed PAM system with a laser PRF of 200 kHz for real-time visualization of microvascular dynamics in the mouse’s ear, and imaged it within a scan range of 1.5 mm (500 pixels) at a B-scan rate of 400 Hz 60 . Yao et al developed a high-speed functional photoacoustic microscopy with a laser PRF of 500 kHz for 3D high-resolution, high-speed imaging of mouse brain, and achieved a scan range of ~ 3 mm (1250 pixels) at a B-scan rate of 400 Hz 35 .…”

Freehand scanning photoacoustic microscopy with simultaneous localization and mapping

“…They may suffer from either bulky probes or a small field of view [20] , [21] , [22] , [23] , [24] , [25] . The state-of-the-art OR-PAM still cannot achieve a large field of view, high flexibility, and fast speed in one system [18] , [19] , [26] , [27] , [28] , [29] , which, however, is urgently needed in biomedical imaging.…”

“…A miniature hybrid resonant-galvo scanner is developed for fast dual-axis scanning. The miniature motor enables a larger scanning range in the slow axis than a traditional dual-axis MEMS scanner [29] , [32] , offering a wide field of view mode. In this mode, FS-PAM can scan over 1.7 × 5 mm 2 at 2 Hz.…”