Rapid HighResolution Mosaic Acquisition for Photoacoustic Remote Sensing Mechanical stages are routinely used to scan large expanses of biological specimens in photoacoustic imaging. This is primarily due to the limited field of view (FOV) provided by optical scanning. However, stage scanning becomes impractical at higher scanning speeds, or potentially unfeasible with heavier samples. Also, the slow scanrate of the stages makes high resolution scanning a timeconsuming process. Some clinical applications such as microsurgery require submicron resolution in a reflectionmode configuration necessitating a method that can acquire large field of views with a small raster scanning step size. In this study, we describe a method that combines mechanical stages with optical scanning for the rapid acquisition of highresolution large FOVs. Optical scanning is used to acquire small frames in a twodimensional grid formed by the mechanical stages. These frames are captured with specific overlap for effective image registration. Using a step size of 200 nm, we demonstrate mosaics of carbon fiber networks with FOVs of 0.8 xc3x97 0.8 mm2 captured in under 70 s with 1.2 xc2xb5m image resolution. Larger mosaics yielding an imaging area of 3 xc3x97 3 mm2 are also shown. The method is validated by imaging a 1 xc3x97 1 mm2 section of unstained histopathological human tissue.

Sensitivity Enhanced Photoacoustic Imaging Using a HighFrequency PZT Transducer with an Integrated FrontEnd Amplifier Photoacoustic (PA) imaging is a hybrid imaging technique that can provide both structural and functional information of biological tissues. Due to limited permissible laser energy deposited on tissues, highly sensitive PA imaging is required. Here, we developed a 20 MHz lead zirconium titanate (PZT) transducer (1.5 mm xc3x97 3 mm) with frontend amplifier circuits for local signal processing to achieve sensitivity enhanced PA imaging. The electrical and acoustic performance was characterized. Experiments on phantoms and chicken breast tissue were conducted to validate the imaging performance. The fabricated prototype shows a bandwidth of 63% and achieves a noise equivalent pressure (NEP) of 0.24 mPaxe2x88x9aHz and a receiving sensitivity of 62.1 xcexbcVPa at 20 MHz without degradation of the bandwidth. PA imaging of wire phantoms demonstrates that the prototype is capable of improving the detection sensitivity by 10 dB compared with the traditional transducer without integrated amplifier. In addition, in vitro experiments on chicken breast tissue show that structures could be imaged with enhanced contrast using the prototype and the imaging depth range was improved by 1 mm. These results demonstrate that the transducer with an integrated frontend amplifier enables highly sensitive PA imaging with improved penetration depth. The proposed method holds the potential for visualization of deep tissue structures and enhanced detection of weak physiological changes.