Low-intensity transcranial focused ultrasound stimulation (tFUS), as a noninvasive neuromodulation modality, has shown to be effective in animals and even humans with improved millimeter-scale spatial resolution compared to its noninvasive counterparts. But conventional tFUS systems are built with bulky single-element ultrasound (US) transducers that must be mechanically moved to change the stimulation target. To achieve large-scale ultrasound neuromodulation (USN) within a given tissue volume, a US transducer array should electronically be driven in a beamforming fashion (known as US phased array) to steer focused ultrasound beams towards different neural targets. This paper presents the theory and design methodology of US phased arrays for the energy-efficient USN at a large scale. For a given tissue volume and sonication frequency (fs), the optimal geometry of a US phased array is found with an iterative design procedure that maximizes a figure of merit (FoM) and minimizes side/grating lobes (avoiding off-target stimulation). The proposed FoM provides a balance between the energy efficiency and spatial resolution in the USN. A design example of a US phased array has been presented for USN in a rats brain with an optimized linear US array. In measurements, the fabricated US phased array with 16 elements (16.77.72 mm3), driven by 150 V pulses at fs = 833.3 kHz, could generate a focused US beam with a lateral resolution of 1.4 mm and pressure output of 1.2 MPa at a focal depth of 12 mm.
|Original language||English (US)|
|Journal||IEEE transactions on biomedical circuits and systems|
|State||Accepted/In press - 2021|
All Science Journal Classification (ASJC) codes
- Biomedical Engineering
- Electrical and Electronic Engineering