Toward Real Time Backward-Mode Pulsed Magnetomotive Ultrasound

Magnetomotive ultrasound (MMUS) is an emerging technique to image in vivo magnetic nanoparticle (MNP) distribution, which is challenging to conventional B-mode ultrasound, and has shown its potential in extravascular ultrasound molecular imaging, monitoring of magnetic nano-drug delivery, and sentinel lymph node identification. To date, MMUS is mainly implemented in forward mode where the imaging object must lie in between an ultrasound probe and an electromagnet, and the imaging frame rate is low, both of which hinder its clinical translation. To facilitate clinical translation of MMUS, here we move toward the development of a real time backward-mode pulsed magnetomotive ultrasound system based on an ultrasound research engine, Prodigy (S-Sharp Corp., Taiwan), featuring an MMUS probe integrating a linear array and an electromagnet. The MMUS probe facilitates the backward-mode MMUS, improving the portability of MMUS. All the processing exploits the fast Prodigy-to-MATLAB interface, PSRT, automatically streaming beamformed ultrafast baseband data to MATLAB for post-processing and image display. Overall, we demonstrate that the imaging frame rate of our MMUS system can achieve 3.4 Hz with free hand scanning, which is about nine time faster than those of the previously reported systems. We believe that such handheld and toward real-time capability would push MMUS toward clinical usage.