Acoustic properties across the human skull

Transcranial ultrasound is emerging as a noninvasive tool for targeted treatments of brain disorders. Transcranial ultrasound has been used for remotely mediated surgeries, transient opening of the blood-brain barrier, local drug delivery, and neuromodulation. However, all applications have been limited by the severe attenuation and phase distortion of ultrasound by the skull. Here, we characterized the dependence of the aberrations on specific anatomical segments of the skull. In particular, we measured ultrasound propagation properties throughout the perimeter of intact human skulls at 500 kHz. We found that the parietal bone provides substantially higher transmission (average pressure transmission 31 +/- 7%) and smaller phase distortion (242 +/- 44 degrees) than frontal (13 +/- 2%, 425 +/- 47 degrees) and occipital bone regions (16 +/- 4%, 416 +/- 35 degrees). In addition, we found that across skull regions, transmission strongly anti-correlated (R = -0.79) and phase distortion correlated (R = 0.85) with skull thickness. This information guides the design, positioning, and skull correction functionality of next-generation devices for effective, safe, and reproducible transcranial focused ultrasound therapies.

Automated summary

The study characterized the impact of different anatomical segments of the skull on transcranial ultrasound propagation. Parietal bone showed higher transmission and smaller phase distortion compared to frontal and occipital bone regions. Across skull regions, transmission was strongly anti-correlated with skull thickness, while phase distortion was correlated with it.