ABSTRACT
In photoacoustic imaging (PAI), biological tissues are typically excited by short-pulsed laser light. Internal organ imaging is typically carried out by acoustic-resolution PAI. With weakly focused or unfocused light excitation, photoacoustic signals can be generated in the diffusive regime and detected by either a single-element focused transducer or a transducer array. A major advantage of acoustic-resolution photoacoustic computed tomography-based molecular imaging over the fluorescence tomography-based technique is the high-spatial resolution at depth. Moreover, PAI is exquisitely sensitive to optical absorption, highly complementary to the contrasts provided by optical coherence tomography and fluorescence imaging. In the past couple of decades, PAI has drawn increasing attention from various research communities, including imaging, chemistry, and biomedicine. A ring-shaped ultrasonic transducer is coaxially and confocally aligned with the optical excitation for maximal sensitivity. A water tank filled with distilled water is used to couple the excited photoacoustic signal to the transducer.
