Super Harmonic Ultrasound Localization Microscopy

Microbubble contrast agents and high frame rate ultrasonography are capable of imaging microvascular structures beyond the diffraction-limited resolution of a typical ultrasound system using a form of localization microscopy. By recovering the locations of bubbles within a long series of sparsely populated contrast-enhanced images, the resolution of the final image is improved by an order of magnitude. The success or failure of this method is determined by the capability of the imaging platform to separate contrast signal from tissue background. Super harmonic imaging is a form of contrast-enhanced ultrasound which produces excellent contrast-to-tissue ratios by exclusively receiving in the frequency band dominated by the harmonic oscillations of microbubbles. In this work, we demonstrate the feasibility of super harmonic ultrasound imaging for localization microscopy in vitro and in vivo.