Retrieving small features in reflection-mode raster-scan optoacoustic mesoscopy (RSOM) using multi-frequency reconstruction

We developed a reflection-mode, raster-scan optoacoustic mesoscopy system, based on a custom-made ultrasonic detector, with an ultra wide bandwidth of 20-180 MHz. To optimally use this bandwidth, we implemented multi-frequency reconstruction. System characterization reveals a 4 mu m axial, and 18 mu m transverse resolution, at penetration depths reaching 5 mm. After characterization, the system was applied to image a zebrafish ex vivo, and an excised mouse ear. In the zebrafish, the lateral line, intestines, eyes, and melanocytes are seen, while in the mouse ear, multifrequency reconstruction recovered the small vessels, otherwise not seen on the image.