Improved in vivo photoacoustic microscopy based on a virtual-detector concept

Recently an in vivo high-resolution backward-mode photoacoustic microscope was developed that shows potential for applications in dermatology and related cancer research. However, the limited depth of focus of the large-numerical-aperture (NA) ultrasonic lens employed in this system causes the image quality to deteriorate significantly in the out-of-focus region. To solve this problem, we devised and explored, for the first time to our knowledge, a virtual-detector-based synthetic-aperture focusing technique, combined with coherence weighting, for photoacoustic microscopy with such a large-NA transducer. Images of phantoms show that the proposed technique improves the −6 dB−6 dB lateral resolution from 49–379 to 46–53