Simultaneous multi-target ultrasound neuromodulation in freely-moving mice based on a single-element ultrasound transducer

Abstract Objective. Ultrasound neuromodulation has become an emerging method for the therapy of neurodegenerative and psychiatric diseases. The phased array ultrasonic transducer enables multi-target ultrasound neuromodulation in small animals, but the relatively large size and mass and the thick cables of the array limit the free movement of small animals. Furthermore, spatial interference may occur during multi-target ultrasound brain stimulation with multiple micro transducers. Approach. In this study, we developed a miniature power ultrasound transducer and used the virtual source time inversion method and 3D printing technology to design, optimize, and manufacture the acoustic holographic lens to construct a multi-target ultrasound neuromodulation system for free-moving mice. The feasibility of the system was verified by in vitro transcranial ultrasound field measurements, in vivo dual-target blood-brain barrier (BBB) opening experiments, and in vivo dual-target ultrasound neuromodulation experiments. Main results. The developed miniature transducer had a diameter of 4.0 mm, a center frequency of 1.1 MHz, and a weight of 1.25 g. The developed miniature acoustic holographic lens had a weight of 0.019 g to generate dual-focus transcranial ultrasound. The ultrasonic field measurements’ results showed that the bifocal’s horizontal distance was 3.0 mm, the −6 dB focal spot width in the x -direction was 2.5 and 2.25 mm, and 2.12 and 2.24 mm in the y -direction. Finally, the in vivo experimental results showed that the system could achieve dual-target BBB opening and ultrasound neuromodulation in freely-moving mice. Significance. The ultrasonic neuromodulation system based on a miniature single-element transducer and the miniature acoustic holographic lens could achieve dual-target neuromodulation in awake small animals, which is expected to be applied to the research of non-invasive dual-target ultrasonic treatment of brain diseases in awake small animals.