Planning for Transcranial Focused Ultrasound Neuromodulation

One of the aspects of safely and accurately targeting brain regions with transcranial focused ultrasound is estimating the trajectory and intensity of the ultrasound waves through the skull. Our projects in this theme include synthesising individual skull maps for each study participant and using computer simulations to estimate the acoustic field through the skull.

Estimating individual skull geometry

The skull accounts for the bulk of transcranial ultrasound attenuation and aberration. To make sure our simulations are as accurate as possible, we plan to create individual skull maps for our research participants. The best way to do this is to obtain a computed tomography (CT) image of the head, however, this involves a CT scan at the hospital. We are working on a deep learning method to synthesise a pseudo-CT from a structural magnetic resonance image (MRI) of the head. This will allow us to estimate skull images in-house using the 3T MRI scanning facility at the Brain Research & Imaging Centre at Plymouth University.

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Clockwise from top left: Structural T1-weighted MR image, actual CT image, pseudo-CT image synthesised from T1-weighted MRI, difference image between pseudo-CT and real CT.

Acoustic simulations

We can estimate and visualise the path of the acoustic pressure wave generated by the ultrasound transducer through the skull using computer simulations. We use a Matlab-based toolbox, k-Wave (Treeby and Cox, 2010), to perform acoustic simulations based on individual skull anatomy and transducer positions to get a better picture of where the ultrasound wave is going and how much pressure is being applied.

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Left to right: Structural T1-weighted MR image, CT image, simulated ultrasound focus in the dorsal anterior cingulate cortex (in colour) on the structural MR image.