Preclinical Study Confirms Safety of Focused Ultrasound Across Three Brain Regions
Repeated low-intensity transcranial focused ultrasound (FUS) is safe for neuromodulation — that is the conclusion of a preclinical study that used magnetic resonance imaging to monitor potential damage in primate brains. Published in the Neuromodulation Journal, the research demonstrated that repeated FUS sessions combined with MR acoustic radiation force imaging (MR-ARFI) produced no detectable tissue damage.
For those working at the intersection of radiology and neuroscience, this result is significant. Transcranial focused ultrasound has been gaining traction as a non-invasive neuromodulation tool, but safety concerns around repeated applications remained unresolved. This study provides robust evidence to advance clinical applications.
Study Design and Targeted Brain Regions
Researchers conducted repeated neuromodulation sessions in six macaque monkeys, targeting three distinct brain regions:
- Ventroposterior lateral (VPL) nucleus of the thalamus — a subcortical target
- Anterior cingulate cortex (ACC) — a cortical target
- Periaqueductal gray (PAG) — a brainstem target
The strategic selection of these three regions spans cortical, deep brain, and brainstem targets, covering a broad spectrum of potential therapeutic applications. Professionals familiar with medical image viewing in radiotherapy will appreciate how standardized protocols enable evaluation of novel techniques like this.
MRI Safety Monitoring: Assessment Tools
Safety assessment employed specific MRI sequences designed to detect potential damage:
- SWI (Susceptibility-Weighted Imaging) — to detect microbleeds
- FLAIR (Fluid-Attenuated Inversion Recovery) — to identify edema and structural injury
These sequences are particularly sensitive to subtle tissue changes, lending robustness to the safety evaluation. MRI proved to be the ideal tool for this type of monitoring, reinforcing the role of advanced medical imaging in translational research.
Results: No Evidence of Damage
MRI signal variability remained within two standard deviations across all sessions, meeting the study’s threshold for no detectable damage. Follow-up intervals ranged from two weeks to over one year, evaluating both short-term and longer-term effects.
Histologic analysis of one PAG target using Hematoxylin and Eosin stains showed “evenly distributed staining without evidence of tissue damage or neuroinflammation.” Notably, no imaging or histologic evidence of injury was found even when MR-ARFI pulses exceeded guideline limits.
Clinical Practice Implications
These results pave the way for developing clinical applications of low-intensity focused ultrasound across various neurological conditions, including chronic pain, treatment-resistant depression, and movement disorders. Confirmed safety in repeated sessions is an essential prerequisite for human clinical trials.
For radiology departments, integrating MRI-guided focused ultrasound represents a promising frontier that could expand the specialty’s scope beyond diagnostics to incorporate non-invasive therapeutic interventions.
Source: Applied Radiology