Description:
Background
Functional ultrasound imaging is a promising neuroimaging technology with potential to unlock next-generation brain-computer interfaces (BCI). However, ultrasound imaging through the skull is limited by the impedance mismatch between bone and brain tissue, causing reflection, scattering, and signal loss, resulting in poor transmission and distorted wavefronts. Existing correction methods recover only part of the lost energy, while microbubble injection-based techniques are impractical for functional imaging and BCIs. These challenges hinder high-resolution, brain-wide neuroimaging through the skull and the development of noninvasive BCI.
Innovation
USC researchers have developed a method to achieve noninvasive, functional ultrasound imaging of the brain by chemically modifying the skull to become acoustically transparent. The process involves topically applying a chelating agent, such as ethylenediaminetetraacetic acid (EDTA), to the intact skull surface. Removal of calcium ions from the bone matrix reduces its acoustic impedance and sound speed to values closely matching those of soft brain tissue. This acoustic property matching minimizes ultrasound reflection, scattering, and wavefront distortion, providing near-lossless transmission of ultrasound waves. By enabling high-resolution, functional ultrasound imaging of brain microvasculature and neural activity through an intact skull, this technology opens new avenues for noninvasive BCI, neuroscience research, clinical diagnostics, and therapeutic interventions.
Advantages
- Noninvasively image brain-wide neural activity with spatial resolution (~20 μm) comparable to no-skull conditions
- Achieves highly sensitive and specific single-trial functional ultrasound imaging
- Safe and reversible treatment using FDA-approved calcium chelators, such as EDTA
Stage of Development
- Ex vivo feasibility experiments performed on human skull samples
- In vivo functional ultrasound imaging and safety experiments performed in mice