Photoacoustic Microscopy and Photoacoustic Computed Microscopy
Photoacoustic microscopy (PAM) is just a variation of photoacoustic tomography (PAT). In general, PAT uses relatively low frequency (up to 5-7 MHz) unfocused transducer(s) to realize deep tissue imaging with the sacrifice of reduced spatial resolution, whereas PAM is based on high frequency (>10 MHz) focused transducer(s) to achieve high spatial resolution with the sacrifice of reduced tissue penetration. Depending upon the spatial resolution and applications, PAM is classified into several categories including optical-resolution PAM (ORPAM), acoustic-resolution PAM (ARPAM), C-scan PAM, photoacoustic computed microscopy (PACM), PAM based on acoustic lens with variable focal length, and confocal PAM using a single multifunctional lens. Here we describe the principles of these PAM approaches.