Transcranial focused ultrasound (tFUS) is a rapidly emerging non-invasive technology capable of selectively targeting specific brain regions. It has demonstrated significant therapeutic potential in the treatment of movement disorders such as essential tremor and Parkinson’s disease tremor. However, despite its promise, the precision and overall effectiveness of tFUS are currently limited by fundamental physical constraints arising from ultrasound propagation through the skull.
When ultrasound waves impinge on the cranial bone, they excite guided elastic modes known as leaky Lamb waves. These waves travel along the skull and radiate acoustic energy into the brain at uncontrolled and often arbitrary angles. The resulting wavefront distortions produce aberrations that degrade the quality of the acoustic focus, reducing targeting accuracy and limiting treatment efficacy. This phenomenon is particularly problematic when attempting to reach peripheral or otherwise difficult-to-access brain regions.
To mitigate these effects, current state-of-the-art tFUS systems rely on patient-specific aberration compensation strategies. These approaches typically involve advanced imaging techniques—such as MRI guidance and X-ray computed tomography—to reconstruct the patient’s skull geometry and compute tailored phase corrections. While effective, such procedures increase cost and complexity, require sophisticated infrastructure, and restrict accessibility. As a result, tFUS remains expensive and not readily available to smaller clinical centers or research laboratories.
LUMEN (Leaky-wave focused Ultrasound through Metamaterial Engineering) proposes a radical shift in this paradigm. Instead of correcting aberrations after they form, the project seeks to control—and potentially exploit—the physical mechanism responsible for them. The central idea is to “dress” the patient with acoustic metasurfaces: engineered, biocompatible structures specifically designed to manipulate wave propagation in a predictable and programmable manner.
By carefully designing these metasurfaces, LUMEN aims to regulate the leaky-wave radiation process directly at its source. In doing so, it becomes possible to reshape how ultrasound energy is transmitted through the skull, enabling more accurate focusing without systematic reliance on complex imaging-based corrections. This approach redefines the focusing mechanism of tFUS, transforming it from a reactive compensation strategy into a proactive wave-control strategy.
The anticipated benefits are substantial. First, reducing dependence on MRI- and CT-based guidance has the potential to make tFUS more affordable and broadly accessible. Second, enhanced control over wave propagation may improve the ability to reach peripheral brain regions that are currently difficult to target. Third, the proposed focusing mechanism is designed to remain effective across diverse skull geometries, making it suitable for a wide range of patients.
Beyond its immediate therapeutic impact, LUMEN will advance fundamental research in wave physics, guided-wave radiation, and acoustic metamaterials. By bridging physics-driven innovation and clinical translation, the project has the potential to reshape non-invasive therapeutic technologies.
Ultimately, LUMEN could transform the treatment landscape for millions of patients suffering from tremor disorders, neuropathic pain, and cancer-related pain. By enabling more inclusive, precise, and cost-effective non-invasive therapies, it promises significant improvements in patient quality of life while contributing to the long-term sustainability of healthcare systems worldwide.
Emanuele Riva, researcher, is the project coordinator.