Transcranial focused ultrasound stimulation with high spatial resolution

Abstract

Background: Low-intensity transcranial focused ultrasound stimulation is a promising candidate for noninvasive brain stimulation and accurate targeting of brain circuits because of its focusing capability and long penetration depth. However, achieving a sufficiently high spatial resolution to target small animal sub-regions is still challenging, especially in the axial direction. Objective: To achieve high axial resolution, we designed a dual-crossed transducer system that achieved high spatial resolution in the axial direction without complex microfabrication, beamforming circuitry, and signal processing. Methods: High axial resolution was achieved by crossing two ultrasound beams of commercially available piezoelectric curved transducers at the focal length of each transducer. After implementation of the fixture for the dual-crossed transducer system, three sets of in vivo animal experiments were conducted to demonstrate high target specificity of ultrasound neuromodulation using the dual-crossed transducer system (n ¼ 38). Results: The full-width at half maximum (FWHM) focal volume of our dual-crossed transducer system was under 0.52 mm 3 . We report a focal diameter in both lateral and axial directions of 1 mm. To demonstrate successful in vivo brain stimulation of wild-type mice, we observed the movement of the forepaws. In addition, we targeted the habenula and verified the high spatial specificity of our dualcrossed transducer system. Conclusions: Our results demonstrate the ability of the dual-crossed transducer system to target highly specific regions of mice brains using ultrasound stimulation. The proposed system is a valuable tool to study the complex neurological circuitry of the brain noninvasively.

Calcium-Modified Silk Patch as a Next-Generation Ultrasound Coupling Medium

“…A stimulation was considered successful if the mouse immediately responded to an ultrasound trigger, and if the voltage amplitude of the EMG spike was larger than three times the noise level. The stimulation was determined to be successful only when both conditions were satisfied. , …”

Ultrasound stimulation for non-invasive visual prostheses

“…Many efforts have recently been made to implement non-invasive visual prostheses, including the investigation of optogenetics ( Barrett et al, 2014 ), photoswitches ( Tochitsky et al, 2016 ), and artificial opsins ( Park et al, 2018 ; Berry et al, 2019 ). In the past decade, ultrasound-based neuromodulation in the brain and peripheral nervous system has gathered huge attention due to its non-invasiveness, deep penetration power through the skull with minimal neural tissue damage ( Lee et al, 2016 ), and sub-mm focusing capability ( Kim et al, 2021 ). Ultrasound has long been used for both diagnostic imaging ( Wells, 2006 ) and therapeutic treatment ( Steiss and McCauley, 2004 ) including cancer tissue destruction ( Hsiao et al, 2016 ), proving its safety.…”

Numerical Evaluation of the Effects of Transducer Displacement on Transcranial Focused Ultrasound in the Rat Brain

“…To ensure accuracy in the numerical simulations, a sensitivity examination of the intracranial field was performed to determine the impact of the geometry and acoustic properties of the model [ 29 , 30 , 31 ]. Park et al proposed a method to find the optimal position of a single-element transducer [ 32 ], and Kim et al designed a dual-crossed transducer system to achieve high spatial resolution for small animals [ 33 ]; however, even though we found the optimal position of the transducer through the numerical simulation, targeting errors could be caused by the registration process between the simulation and experiments. As for numerical studies performed with rodents, Constans et al simulated the pressure field and thermal rise under a large range of frequencies for the specific target area.…”