Search for: All records

Transcranial focused ultrasound stimulation (tFUS) has emerged as a potential noninvasive therapeutic technology. Due to skull attenuations at high ultrasound (US) frequencies, successful tFUS with sufficient penetration depth requires sub-MHz US waves, leading to relatively poor stimulation specificity particularly in the axial direction (perpendicular to the US transducer). This shortcoming can potentially be overcome by utilizing two individual US beams properly crossed in time and space. For large-scale tFUS, a phased array is also required to dynamically steer focused US beams at desired neural targets. This article presents the theoretical foundation and optimization (through a wave-propagation simulator) of crossed-beam formation using two US phased arrays. 

Ultrasonic (US) neuromodulation has emerged as a promising therapeutic means by delivering focused energy deep into the nervous tissue. Low-intensity ultrasound (US) directly activates and/or inhibits neurons in the central nervous system (CNS). US neuromodulation of the peripheral nervous system (PNS) is less developed and rarely used clinically. The literature on the neuromodulatory effects of US on the PNS is controversial, with some studies documenting enhanced neural activities, some showing suppressed activities, and others reporting mixed effects. US, with different ranges of intensity and strength, is likely to generate distinct physical effects in the stimulated neuronal tissues, which underlies different experimental outcomes in the literature. In this review, we summarize all the major reports that document the effects of US on peripheral nerve endings, axons, and/or somata in the dorsal root ganglion. In particular, we thoroughly discuss the potential impacts of the following key parameters on the study outcomes of PNS neuromodulation by US: frequency, pulse repetition frequency, duty cycle, intensity, metrics for peripheral neural activities, and type of biological preparations used in the studies. Potential mechanisms of peripheral US neuromodulation are summarized to provide a plausible interpretation of the seemly contradictory effects of enhanced and suppressed neural activities of US neuromodulation.