Optical-resolution Photoacoustic Microscopy Based on a Low Cost Laser Diode Source

Abstract

Although the potential of photoacoustic tomography for various biomedical applications has been demonstrated sufficiently over the past two decades, its spread into actual fields in demand is still poor due to the high cost of laser sources, which play a key role in related systems—usually, its cost easily exceeds 20k USD, accounting for more than 50% of the entire system cost. In this study, we developed an optical-resolution photoacoustic microscopy (PAM) system with a transverse resolution of ~20 μm. It works based on the pulsed driving of a 450 nm laser diode which was manufactured to provide a 7 W average power at a continuous wave operation mode. Achieved pulse width and energy were ~20 ns and ~300 nJ, respectively, at 1 kHz repetition rate. Compared to conventional PAMs, in which a Q-switched diode pumped solid state laser providing a 532-nm wavelength is usually engaged, the applied 450-nm wavelength is the one where the blood absorption is ~1.4 times greater than that in 532 nm, thereby bringing the effect of a SNR increase when applied to a live tissue. Moreover, the implemented system features its easy accessibility to a target tissue because the scanning head was implemented to have a small footprint by applying a GRIN lens with large numerical aperture for the distal illumination optics. Not to mention additional features, it was the key benefit that the hardware cost for implementing a necessary light source could be reduced to less than 200 USD. In this poster, we share several interesting results of the new PAM system in terms of the performance test and imaging validation.