Implementation of a Skull-Conformal Phased Array for Transcranial Focused Ultrasound Therapy.

Objective: To implement a skull-conformal phased array for ultrasound-guided transcranial focused ultrasound therapy with improved patient comfort.

Methods: Using patient-specific computed tomography and MRI neuroimaging data, tightly-conforming helmet scaffolds were designed computationally. The helmet scaffolds were designed to hold reusable transducer modules at near-normal incidence in an optimal configuration for the treatment location(s) of interest. Numerical simulations of trans-skull ultrasound propagation were performed to evaluate different conformal array designs and to compare with hemispherical arrays similar to those employed clinically. A 4096-element phased array was constructed by 3D printing a helmet scaffold optimised for an ex vivo human skullcap, and its performance was evaluated via benchtop and in vivo experiments.

Results: Acoustic field measurements confirmed the system's ability to focus through human skull bone using simulation-based transcranial aberration corrections. Preliminary in vivo testing demonstrated safe trans-human skull blood-brain barrier (BBB) opening in rodents.

Conclusion: Patient-specific conformal ultrasound phased arrays appear to be a feasible and safe approach for conducting transcranial BBB opening procedures.

Significance: Skull-conformal phased arrays stand to improve patient comfort and have the potential to accelerate the adoption of transcranial FUS therapy by improving access to the technology.