Optical resolution photoacoustic microscopy using novel high-repetition-rate passively Q-switched microchip and fiber lasers

Abstract

Abstract. Optical-resolution photoacoustic microscopy ͑OR-PAM͒ is a novel imaging technology for visualizing optically absorbing superficial structures in vivo with lateral spatial resolution determined by optical focusing rather than acoustic detection. Since scanning of the illumination spot is required, OR-PAM imaging speed is limited by both scanning speed and laser pulse repetition rate. Unfortunately, lasers with high repetition rates and suitable pulse durations and energies are not widely available and can be cost-prohibitive and bulky. We are developing compact, passively Q-switched fiber and microchip laser sources for this application. The properties of these lasers are discussed, and pulse repetition rates up to 100 kHz are demonstrated. OR-PAM imaging was conducted using a previously developed photoacoustic probe, which enabled flexible scanning of the focused output of the lasers. Phantom studies demonstrate the ability to image with lateral spatial resolution of 7±2 m with the microchip laser system and 15± 5 m with the fiber laser system. We believe that the high pulse repetition rates and the potentially compact and fiber-coupled nature of these lasers will prove important for clinical imaging applications where real-time imaging performance is essential.

Realtime portable in vivo optical-resolution photoacoustic microscopy

“…Fitting individual carbon fiber signal amplitude to a Gaussian function, the full-width-half-maximum is calculated ~ 9 µm. However if we take into account the width of the carbon fibers itself, the estimated optical lateral resolution is calculated as ~ 7µm [3]. Considering the fast and slow scanning speed we managed to form these images with four C-scans frame per second and 800 B-scans per second.…”

“…Different forms of PA imaging have been recently reported such as photoacoustic tomography (PAT) [4,5] and dark-field photoacoustic microscopy (PAM) [6,7]. Photoacoustic imaging can be used for functional and molecular imaging such as imaging of blood oxygen saturation, imaging of gene expression, and imaging of contrast agents and optically absorbing nanoparticles [3,8].…”

“…The laser-induced ultrasonic waves related to the optical absorption are detected in order to image the 3D distribution of the optical energy deposition in targets [1]. PA imaging is a popular research topic for early diagnosis and monitoring of diseases such as cancer since it is a safe technique with high-contrast and high spatial resolution [2,3]. PA imaging takes advantage of non-ionizing waves which have no health hazards, compared with some other techniques such as x-ray computed tomography [2].…”

In vivo optical resolution photoacoustic microscopy using glancing angle-deposited nanostructured Fabry–Perot etalons

“…Detected signal levels displayed a linear relationship with pulse energy. The optical lateral resolution was estimated ∼7 μm [ 13]. Both images are formed using a 3 mm × 3 mm FPI.…”

Multimodality Raman and photoacoustic imaging of surface-enhanced-Raman-scattering-targeted tumor cells

“…The lateral resolution of the PAM imaging subsystem was measured as ∼50 μm by imaging a ∼7.5 μm carbon fiber. 18 To further demonstrate the capability of applying our method for the detection of CTCs under native targeting process, instead of incubating HeLa cells with nanoparticles before imaging, we first mixed HeLa cells with rat blood, and then added with folate-conjugated SERS nanoparticles and magnetic nanoparticles. HeLa cells (∼1 × 10 5 or ∼5 × 10 4 ) were first mixed with 1 mL rat blood for 10 min.…”