Photoacoustic Super-Resolution Imaging using Laser Activation of Low-Boiling-Point Dye-Coated Nanodroplets in vitro and in vivo

In this study, a photoacoustic super-resolution imaging technique was developed through imaging the activation of Cyanine 7.5-coated phase-change nanodroplets using a preclinical photoacoustic imaging system and localizing the activated droplets. As a proof-of-concept experiment, photoacoustic images of flowing dye-coated nanodroplets in microfluidic channels were obtained with a cylindrically focused curved-array. Experimental results showed that super-resolution images can resolve the microfluidic channels which cannot be resolved by conventional beamformed images. The results also showed that the dye-coated phase-change nanodroplets can be optically activated in vivo and the activation signals can be separated from the image background by applying singular value decomposition filtering, and be used for further super-localization processing. Such nanodroplets can offer better biocompatibility, as well as more flexible and controllable droplet activation rates, with potential for super-resolution imaging of static and extravascular targets, compared to existing contrast agents used in existing localization-based photoacoustic super-resolution imaging techniques.