Design and evaluation of phased array transducers for deep brain stimulation in nucleus accumbens region of the rat brain

Transcranial focused ultrasound (tFUS) is a novel noninvasive neuromodulation method that has many potential application in the treatment of neuropsychiatric and neurologic disorders. One such application is addiction control through neuromodulation. It is hypothesized that proper stimulation of the nucleus accumbens can help in controlling or suppressing addictive behavior such as alcohol, drug and internet addiction. In this paper, we show the design and characterization of 2.5 MHz and 5 MHz transducer arrays for rat models. Designing and manufacturing an ultrasound probe for such an application presents several challenges: limited acoustic aperture in the skull, strong reflectance and attenuation of the skull, and focal size limitations due to the depth and size of the nucleus accumbens. We show with simulations and ex-vivo skull experiments that we can target nucleus accumbens in rats with reasonable accuracy and deliver enough acoustic energy across the rat skull while targeting both nucleus accumbens sites simultaneously.