The Work is the Next Step Forward in Focused Ultrasound Therapy for Essential Tremor

In 2011, the University of Virginia's Dr. Jeffrey Elias, a neurosurgeon at UVA Health, was among the first in the world to use focused ultrasound technology to treat patients with essential tremor, a condition akin to Parkinson’s disease that affects up to 10 million Americans.

Ten years later, UVA has become an epicenter for focused ultrasound technology, which uses concentrated, high-intensity soundwaves to generate heat so that a physician, guided by an MRI machine, can target specific areas without damaging surrounding tissue. It is less invasive than traditional surgical options, with fewer side effects and shorter recovery times.

UVA neurosurgeons are sounding out the future of focused ultrasound to treat tremor, epilepsy, cancer and more—but it’s magnetic resonance imaging experts like professor Craig Meyer who are expanding the capabilities of the MRI guidance systems used to manage the surgical procedure. Meyer, a professor in UVA’s Department of Biomedical Engineering, will use a grant from the National Institutes of Health to increase the speed and enhance the safety of focused ultrasound therapy for the treatment of essential tremor.

“Through our clinical experience, we have identified several critical areas for improvement,” Meyer said. “In the process of achieving these goals, we will be applying MRI in ways that have not been attempted before.”

Professor Craig Meyer who is developing magnetic resonance imaging (MRI) techniques for rapid acquisition and processing of image data.

Craig Meyer, a professor of biomedical engineering at the University of Virginia, develops magnetic resonance imaging (MRI) techniques for rapid acquisition and processing of image data in the setting of cardiovascular disease, neural diseases, and pediatrics, using tools in physics, signal processing, image reconstruction, and machine learning.

In focused ultrasound therapy for essential tremor, an acoustic lens is used to concentrate multiple intersecting beams of ultrasound energy on the thalamus tissue in the brain responsible for the tremor. The process is analogous to burning a hole in a piece of paper with a magnifying glass. Magnetic-resonance imaging is used to guide clinicians to the precise location to be ablated, monitor intensity of the application, and make adjustments as needed to obtain the best patient outcomes. 

One issue with current approaches is that clinicians are limited to using two-dimensional MRI images to ensure the focused ultrasound is targeted at the damaged tissue. In the course of zeroing in on the precise location, they have to generate a series of images in different planes. This is a time-consuming process.

One aim of the grant is to find ways to create real-time three-dimensional imaging, which in addition to saving time, will help clinicians determine how close the target is to sensitive areas of the brain. “Having a 3D image is one way to reduce the possibility of inadvertent side effects,” Meyer said.

During the procedure, patients get immediate relief from essential tremor as the ablation proceeds, but surgeons do not have a way to independently determine whether they have achieved the most possible benefit without damaging healthy tissue. Meyer and his colleagues will develop a technique to provide interim assessments between sonications to help clinicians fine-tune their results.

Another challenge using focused ultrasound to treat essential tremor is that a portion of the ultrasound energy is absorbed by the skull on its way to the thalamus. As a result, there is the danger that the skull can heat up sufficiently to damage nearby tissue.

Currently, there is no way to directly measure the skull’s temperature during the procedure. Clinicians use information from a CT scan taken the day before to determine a safe wait time between sonications. Meyer proposes to use the spiral MRI techniques his lab has pioneered to deliver virtually real-time, three-dimensional thermography images in a very difficult imaging environment.

“No one has ever combined skull and brain thermometry,” Meyer said. “This will be a really exciting problem to solve that could have broad application.”

The U.S. Food and Drug Administration has approved focused ultrasound as a therapy for Parkinson’s disease, uterine fibroids, bone metastases, prostate cancer, and benign prostatic hyperplasia as well as for essential tremor—and researchers are investigating its use for scores of other conditions. “Our goal is not just to improve the speed and efficacy of essential tremor treatment,” Meyer said. “Our hope is that the new techniques we develop will provide the groundwork for employing focused ultrasound more broadly.”

The research team includes Meyer, Elias, Wilson Miller (UVA Radiology and Medical Imaging), William Grissom (Vanderbilt University Biomedical Engineering), Steven Allen (UVA BME) and Xue Feng (UVA BME).  Allen and Feng are former trainees in Meyer’s group and now research assistant professors at UVA. The group’s work is supported by the National Institutes of Health grant R01EB028773.