Acoustic Coupling for Double-Blind Human Low-Intensity Focused Ultrasound Neuromodulation
Discuss this preprint
Start a discussion What are Sciety discussions?Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
Objective
Low-intensity focused ultrasound (LIFU) is a non-invasive neuromodulation technique with the potential for precise targeting of small and deep human brain circuitry. To ensure rigorous and reproducible effects, it is necessary to implement double-blinding to mitigate potential experimental biases. This study innovates on previous ultrasound coupling methods by embedding a 3D-printed thermoplastic disc in a high-density gel-polymer matrix to create identical gel-plastic coupling devices that either transmit (verum) or block (sham) ultrasound.
Methods
We evaluated varying thicknesses (1.5 mm, 2,0 mm, 2.5 mm) and infill densities (25%, 50%, 75%, and 100%) of Acrylonitrile Butadiene Styrene (ABS) for insertion loss and effects on beam characteristics across relevant human neuromodulation frequencies from 0.2 – 1 MHz.
Results
ABS at 1.5 mm thickness and 50 % infill had the lowest insertion loss at 0.50 MHz of 0.9 ± 0.04 dB demonstrating acoustic transparency suitable for a verum device. For the sham device, we introduced an internal air gap that produced 31 dB insertion loss at 0.50 MHz. The verum device demonstrated minimal effects on the beam shape with a radial peak shift of 0.3 ± 0.2 mm and an average axial shift of 0.5 mm.
Discussion
This novel gel-plastic coupling device can be tailored to most LIFU transducer shapes and is designed to support double-blind protocols by maintaining visual and tactile indistinguishability while controlling transmitted energy. This method provides a cost-effective and easily implementable solution for double-blinding in human LIFU studies to improve the reliability and rigor of experimental outcomes.
