Development of a Phased Array Focused Ultrasound Transducer for Two-photon Microscopy Guided Neural Studies

Focused ultrasound combined with intravenously injected microbubbles is a promising non-invasive therapy capable of temporarily disrupting the blood-brain barrier for targeted drug delivery. Established in vivo experiments on rodent models combine focused ultrasound treatment with two-photon microscopy imaging to improve understanding of microvasculature response. A phased array, an advanced ultrasound therapy device, was successfully developed to improve pressure transmission in these experiments. An investigation of transducer sensitivity to setup equipment suggested modifications to setup procedures, for example recording objective position, may improve in situ pressure estimates. A ring array composed of 50 lateral mode elements, geometry determined by pressure field simulations, was successfully fabricated. Fibre optic hydrophone pressure field measurements confirmed the device had an appropriate focal size (0.7mm diameter x 4mm axial length) and reached therapeutic pressure levels (>0.5MPa). Ex vivo transcranial measurements demonstrated moderate focal correction and off-axis steering capabilities that may improve experimental throughput and target alignment.MAS