Pattern Interference Radiation Force (PIRF) Based on Large-scale Focused Transducer Using Fresnel Lens

Using a focused ultrasound transducer is one of the most preferred methods for neurostimulation. Due to its high spatial resolution, high penetration depth, ultrasonic property, and its ability to be combined with other methods, a focused ultrasound transducer is suitable for non-invasive brain neurostimulation and is widely used. Generally, only one transducer is used or all transducers face one direction for focusing. Unlike previous cases, neurostimulation using a pattern interface radiation force (PIRF) uses more than two focused transducers and makes standing wave patterns inside the brain for neurostimulation. This paper presents the fabrication and application of a large-scale focused transducer using a Fresnel lens for PIRF application. The focused transducer is made with polydimethylsiloxane (PDMS) and a hybrid-type piezoelectric (PZT) ceramic plate similar to PZT-4 with a size of 100 mm × 80 mm × 2.2 mm. The lens was designed for a 1-MHz frequency, which is the center frequency of the PZT plate. Using these two transducers, a standing wave pattern was created inside the skull, and the radiation force was calculated using the measured pressure field.