Fast Acoustic Wave Sparsely Activated Localization Microscopy (Fast-AWSALM) Using Octafluoropropane N Anodroplets

A crucial challenge in the application of ultrasound super-resolution imaging using microbubbles to the clinic is the long acquisition time together with the motion during the data acquisition. In this study, fast acoustic wave sparsely activated localization microscopy (fast-A WSALM)is developed to simultaneously image, activate and deactivate octafluoropropane nanodroplets during high-frame-rate planewave ultrasound imaging to achieve ultrasound super-resolution images on a sub-second timescale. This work demonstrates in vitro fast-A Wsalmof a non-flow 200-micron-tube phantom. Firstly, experimental results show that the octafluoropropane nanodroplets can be activated by the plane-wave pulses, whereas acoustic droplet vaporization has only been achieved using focused single element transducers or linear-array probes with focus-wave transmission in previous literature. The activation of nanodroplets via plane-waves without the need of using focused-transmit waves enables a faster imaging and activation acquisition. Second, the results show the fast-AWSALM can give a better estimation of the tube diameter (190 um)where standard B-mode ultrasound image cannot (550 um), In summary, this study demonstrates the potential of fast-A WSALM, a super-resolution techniques using nanodroplets, which can generate super-resolution images in milliseconds and does not require flow or a precise control of contrast agent concentration.