LAUSR

Prior research has demonstrated that Passive Acoustic Mapping (PAM) enables real-time monitoring of cavitation activity occurring within the vasculature to achieve drug delivery and/or opening of the Blood Brain Barrier. In the present work, we focus on whether sub-micron cavitation nuclei can be imaged once extravasated. This would provide a means of determining both vascular permeability before or after ultrasound exposure, and real-time monitoring of successful drug delivery. A key challenge in achieving these objectives is the spatial resolution of PAM. A novel bistatic setup was used to achieve sub-millimetre resolution both axially and transversely to two imaging arrays. A vertically oriented flow channel in a tissue mimicking phantom was placed at the focus of two perpendicular confocal HIFU transducers, each with a coaxial linear imaging array. Sequential acoustic excitation at 0.5 or 1.55 MHz was used to first extravasate, and then re-excite the nuclei once extravasated. The lower frequency creat...