Session: 16-02-01: Poster Session: NSF Research Experience for Undergraduates (REU), NSF Posters

Paper Number: 99682

99682 - Investigation on Acoustic Holographic Lenses for Low Intensity Transcranial Neuromodulation 

Chronic pain is a debilitating condition that is an enigma for both doctors and their patients. The CDC estimated that 20.4% of US adults experience chronic pain which imposes tremendous burdens on the healthcare system and can severely affect a patient's quality of life. The most common form of treatment is medication, though it often comes with undesired side effects. Desperate patients may also turn to drastic and irreversible surgical procedures even if such procedures are prone to fail. Neuromodulation is an emerging tool for the treatment of chronic neuropathic pain by altering the nerve activity through the targeted delivery of a stimulus. Current neuromodulation techniques like transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are limited due to poor spatial resolution and high attenuation when targeting tissue deep within the brain. This presentation will discuss the alternative therapy known as tFUS, or transcranial focused ultrasound. tFUS is a new and promising non-invasive technique for safely inducing transient plasticity deep within the brain by sending ultrasound pulses with high spatial precision and depth. In this work, a 3D printed holographic lens is designed using time-reversal and phase conjugation techniques to compensate for skull aberrations as well as target the ventral posterolateral nucleus (VPL). We verify our work using numerical simulations and submerged experiments using a 3D printed skull phantom. Firstly, computed tomography (CT) and magnetic resonance (MR) images are used to obtain the geometry and the acoustic properties of the skull. Simple thresholding is used to infer the skull geometry from the CT images. On top of the previously established skull domain, additional segmentation is done on MR images to derive the geometry of the skin, cerebrospinal fluid, and brain tissue. Secondly, by utilizing the acoustic simulations toolbox “k-wave” the lens is designed using time-reversal techniques that account for the inhomogeneities in the propagation medium and the skull. Developing accurate physical models is essential for providing patients with fast and personalized therapeutic procedures without the need for any invasive interventions. To this end, 3D multiphysics finite element simulations (FEM) using COMSOL 5.4 were also implemented to study the effects of elastic waves propagation, i.e. shear effects, and attenuation of the skull on the spatial distribution of the sound field in the skull. Finally, experiments in a water tank are performed to verify our numerical and computational findings. We will also discuss focused ultrasound (FUS) as a promising noninvasive therapeutic technology with applications beyond neuromodulation. These applications include items like focused ultrasound-induced heating for non-invasive tissue ablation. In addition, using FUS and microbubbles to break down the blood-brain barrier for enhanced drug delivery. Lastly, FUS can be utilized as non-invasive "tweezers" to manipulate various objects including blood clots or nanoparticles.

Presenting Author: Eric Hoffmann Virginia Tech

Presenting Author Biography: Eric Hoffmann is an undergraduate senior at Virginia Tech. Currently, he works as a NSF REU Researcher in the Multiphysics Intelligent and Dynamical Systems Lab.

Authors:

Eric Hoffmann Virginia Tech
Ahmed Sallam Virginia Tech
Shima Shahab Virginia Tech