The Work is the Next Step Forward in Focused Ultrasound Therapy for Essential Tremor
In 2011, the University of Virginia’s 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 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.
While UVA neurosurgeons are pioneering the use of focused ultrasound to treat tremor, epilepsy, cancer and more, behind the scenes, experts like Craig Meyer are working to expand the capabilities of the MRI guidance systems used to manage the surgical procedure.
Meyer, a professor in UVA’s Department of Biomedical Engineering, has been awarded 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.
In focused ultrasound therapy for essential tremor, an acoustic lens is used to concentrate multiple intersecting beams of ultrasound energy on the brain’s thalamus tissue, which is responsible for the tremor. The process is analogous to burning a hole in a piece of paper with a magnifying glass. MRI technology 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 that 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 would 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 greatest benefit possible without damaging healthy tissue. Meyer and his colleagues are also working to develop a technique to provide interim assessments between sonications to help clinicians fine-tune their results.
Another challenge when 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. Instead, 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, benign prostatic hyperplasia and 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 consists of Meyer, Elias, Steven Allen of Brigham Young University, Xue Feng of UVA’s biomedical engineering department, William Grissom of Vanderbilt University and Wilson Miller of UVA’s radiology department.
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