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Non-contact laser ultrasonic technique has been increasingly implemented for non-destructive inspections in harsh environments, high-temperature fields, and components having complex geometries. However, the poor signal-to-noise ratio and low amplitude of laser generated ultrasonic signals under a thermoelastic regime severely restrict its applications. Here, a sensitivity-enhanced all-optical probe was proposed for laser ultrasonic non-destructive testing. It consists of an optical sensor and an ellipsoidal acoustic cavity, where an optical sensor is placed at one focus of the cavity, and the detection point is set at another focus. The ultrasound signals are focused through the cavity and detected by the optical sensor. Side-by-side comparison experiments were carried out, and the results show that the probe can improve the signal amplitude by about 7.8 times compared to using a traditional optical sensor alone. The probe can make laser ultrasound detect defects with lower laser energy, which is of great significance to improve the efficiency of non-contact defect detection. [ABSTRACT FROM AUTHOR]

In vivo wide-field brain microscopy has remained a non-trivial challenge in life science research, which would provide indispensable preclinical insight into the whole-brain metabolism and hemodynamic. Here, we developed an ultra-compact micro-photoacoustic tomography (μPAT) system for fast brain imaging equipped with a 10 MHz 256-element full-ring ultrasound transducer array and 100 MS/s/ch multi-channel parallel data acquisition. The system design and calibration are presented in detail, along with the 62 μm in-plane resolution comparable to the level of acoustic-resolution photoacoustic microscopy. The μPAT system provided the ability to noninvasively use high-resolution mapping of the microvascular network of the full-view brain at different depths, cerebral ischemia, and intracerebral foreign-body. Ultra-compact μPAT holds great potential to take the technology out of the lab for preclinical imaging and clinical translation. [ABSTRACT FROM AUTHOR]

In vivo identification of viable and thermally coagulated blood in a burn wound can be used to profile the type, extent, and site of the burn, thus assisting the removal of necrotic tissue in preparation for skin grafts. Recently, intensive research on photoacoustic imaging (PAI) has been conducted to evaluate burn injury. However, most PAI systems usually take the approach of direct physical contact of an acoustic detector or an impedance matching medium with the vulnerable burned skin, which exposes significant limitations on the diagnosis of burn injuries. Here, we present a noncontact PAI system, based on a custom designed air-coupled ultrasonic transducer, enabling in vivo noncontact vasculature to be imaged without contrast agents. Using the natural difference in light absorption between coagulated and non-coagulated blood at the wavelength of 532 nm, this PAI system possesses an immanent advantage to discriminate viable and thermally coagulated blood in burned tissues. Phantom experiments and burned rabbit's skin imaging have been implemented to demonstrate that the noncontact PAI technique could be valuable in the adjuvant diagnosis and observation of burns. [ABSTRACT FROM AUTHOR]

Optical-resolution photoacoustic microscopy (OR-PAM) has been significantly improved in terms of spatial resolution, detection sensitivity, imaging speed, and penetration depth. However, the popular producibility of OR-PAM system is still limited by the size and cost of solid-state laser excitation. Here, we developed a portable laser-diode-based OR-PAM (LD-OR-PAM) system using a pulsed semiconductor laser source, which was operated at 905 ± 15 nm with a pulse energy as low as 4.9 μJ. The measured lateral resolution has been improved to ∼1.5 μm from hundreds of microns. The compact and inexpensive natures of LD-OR-PAM would promote the potential clinical applications such as in dermatology. [ABSTRACT FROM AUTHOR]