Photoacoustic microscopy enters the mainstream

MicroPhotoAcoustics (MPA) has developed a commercial PAM system with switchable optical and acoustic resolution (OR- and AR-PAM), using multiple patents licensed from the lab of Lihong Wang. The system includes different excitation sources for the different modes. The sources for OR-PAM are two kilohertz-tunable, Q-switched, fiber-based solid-state lasers offering a 5 kHz pulse repetition rate and 9 ns pulse duration with 532 and 559 nm,4 respectively, and output to achieve functional photoacoustic tomography for sO2 (oxygen saturation of hemoglobin) imaging. The excitation source for AR-PAM is a Ti:sapphire laser system with a selection of up to eight output wavelengths, in the range from 700 to 900 nm to achieve deep-tissue imaging. Switching between OR- and AR-PAM is a matter of replacing a single-mode fiber with a multimode fiber configured with a different collimator lens. In OR-PAM mode, the system provides up to 1 mm penetration depth and resolutions of 5 μm lateral and 30 μm axial, while AR-PAM offers up to 3 mm imaging depth and resolutions of 45 μm lateral and 30 μm axial. Both modes use raster scan to form a 3D image. Researchers have used the system for a range of applications, including preclinical neural imaging; imaging of cell nuclei in intestine, ear, and leg; and clinical human imaging of finger cuticle.