Acoustic coupling pads for the control of ultrasound neuromodulation exposure

Abstract

We have developed acoustic coupling pads that facilitate single-blind and double-blind neuromodulation experiments by selectively transmitting ultrasound without affecting the audible sound. The pads were made from a skin-safe two-part silicone with little to no ultrasonic attenuation, that also provided the necessary acoustic properties, stability and flexibility. To inhibit the transmission of ultrasound, a foam disk was imbedded into the pad during the manufacturing process. The design goal for acoustic attenuation was −40 dB. 20 sets of transmit pads and non-transmit pads were fabricated. Acoustic transmission loss was measured in a water tank with a 60 mm diameter, 80 mm focus circular disk transducer operated at 650 kHz and a standard hydrophone (Reson TC4038). Transmit pads had an average of −0.4 dB loss; non-transmit pads met the required −40 dB loss (average: −47.4 dB). An operator experienced with ultrasound treatments was unable to distinguish them by visual inspection or casual physical manipulation. An experienced subject exposed to a typical treatment regimen was not able to distinguish any audible difference. The acoustic coupling pads create identical testing situations for single-blind and double-blind studies for neuromodulation treatments so that neither the patient nor the operator administering the treatment can distinguish which patient group received the ultrasound treatment and which did not.