Figure 1.

The handheld, real-time photoacoustic (PA) imaging system. One custom-designed optical parametric oscillator (OPO) diode-pumped by a Nd:YAG laser at 532 nm was employed for laser illumination with a fast-wavelength-tuning function for each pulse. The customized fiber bundle was used to deliver the laser light onto the target. Light was evenly distributed into the two arms with a rectangular output size of 16.5 mm × 0.8 mm. A 128-channel research ultrasound (US) platform with a high-frequency array transducer was used for recording the generated PA signal. For proof of simulation results, the PA probe (i.e., fiber bundle with US transducer array) was mounted on the linear and rotation stages to adjust the interval and angle of the two arms. For phantom and in vivo studies (e.g., small animal experiments), the XYZ 3-axis scanning stage with frame holder was used to precisely/automatically image the region of interest (ROI) of the target in either the X or Y direction.