Handheld Photoacoustic Microscopy Probe

Abstract

Optical resolution photoacoustic microscopy (OR-PAM) is a non-invasive, label-free method of in vivo imaging with microscopic resolution and high optical contrast. Based on intrinsic contrasts, OR-PAM has expanded to include in vivo vessel imaging, flow cytometry, physiological parameter analysis, and single-cell characterization. However, since conventional OR-PAM systems have a fixed tabletop configuration, a large system size, and slow imaging speed, their use in preclinical and clinical studies remains limited. In this study, using microelectromechanical systems (MEMS) technology, we developed a handheld PAM probe with a high signal-to-noise ratio and image rate. To enable broader application of the OR-PAM system, we reduced its size and combined its fast scanning capabilities into a small handheld probe that uses a 2-axis waterproof MEMS scanner (2A-WP-MEMS scanner). All acoustical, optical, and mechanical components are integrated into a single probe with a diameter of 17 mm and a weight of 162 g. This study shows phantom and in vivo images of various samples acquired with the probe, including carbon fibers, electrospun microfibers, and the ear, iris, and brain of a living mouse. In particular, this study investigated the possibility of clinical applications for melanoma diagnosis by imaging the boundaries and morphology of a human mole.

Non‐invasive imaging in dermatology and the unique potential of raster‐scan optoacoustic mesoscopy

“…The penetration depth of such systems is, however, fundamentally limited by light scattering and, therefore, similar to that of RCM or MPM. To the best of our knowledge, microscopic optoacoustic devices have not yet entered clinical research . Optoacoustic mesoscopy methods use non‐focused illumination schemes in combination with a focused ultrasound detector, which enables imaging to depths of several millimetres while keeping high resolution .…”

“…To the best of our knowledge, microscopic optoacoustic devices have not yet entered clinical research. 46,[50][51][52][53] Optoacoustic mesoscopy methods use non-focused illumination schemes in combination with a focused ultrasound detector, which enables imaging to depths of several millimetres while keeping high resolution. [54][55][56][57][58] A fundamental limitation of previous systems has, however, been the narrow bandwidth of the applied ultrasound detectors.…”

In vivo label‐free functional photoacoustic monitoring of ischemic reperfusion

“…The dual‐wavelength MEMS‐OR‐PAM system was retrofitted based on a commercial mechanical‐scanning PAM system (MicroPhotoAcoustics, Inc., Ronkonkoma, New York) . A customized water‐immersible MEMS scanner (OPTICHO, Pohang, Gyeongbuk, Republic of Korea) was installed to achieve high imaging speed for dual‐wavelength imaging. To quantify sO2 in the blood vessels, the pulse‐to‐pulse energy variation of the nanosecond laser source needed to be compensated for.…”

Acoustic resolution photoacoustic microscopy based on microelectromechanical systems scanner

“…The introduction of water-immersible MEMS scanner has improved the OR-PAM imaging speed significantly compared to raster mechanical stage scanning and also helps to develop handheld based devices [21][22][23]. The imaging depth achievable using OR-PAM limits the use of this high-resolution technology [18,24,25].…”