High-resolution photoacoustic tomography in vivo

An in vivo backward-mode photoacoustic microscope was recently developed that employs a high frequency, broadband, large numerical aperture (NA) focused ultrasonic transducer to provide high resolution and high sensitivity. However, out of the focus region, the limited depth of focus deteriorated the image quality significantly. Based on a virtual-detector concept, we devised and implemented a synthetic aperture focusing technique in combination with coherence weighting to overcome this drawback. This technique improved the -6-dB lateral resolution from 50-265 microns to 46-55 microns and increased the SNR by up to 23 dB. In vivo experiments showed that the technique provided a clearer representation of the vascular distribution in the dorsal dermis of a rat.