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Transcranial focused ultrasound (tFUS) is ultrasound aimed through the skull, without surgery, onto targets at the brain's surface or deep inside it. At low intensity, with little heating, the pulses appear to act mechanically on nerve-cell membranes, altering pressure-sensitive proteins and the opening and closing of ion channels; a thermal action is unlikely at these intensities. At higher intensities, the ultrasound can damage or destroy tissue.
Transcranial focused ultrasound (tFUS) focuses ultrasound noninvasively onto cortical or deep neural targets. A review describes focusing by constructive interference with wavelength-scale spatial resolution, about 3 mm at 0.5 MHz, and reports strong skull scattering above 1 MHz. A 256-element helmet-shaped array operates at 555 kHz. Its CT-informed full-wave treatment-planning model predicts an average in-situ focus of 2.2 × 2.2 × 3.1 mm at −6 dB at the lateral geniculate nucleus target, compared with 2.0 × 2.3 × 2.6 mm in water; these dimensions follow the helmet axes. A reviewed pulsed protocol uses 0.50 MHz ultrasound, 0.36 ms pulses at 1 kHz for 500 ms, and a spatial-peak pulse-average intensity of 16.95 W/cm². Low-intensity ultrasound appears to act mechanically on neuronal membranes, modifying mechanosensitive proteins and ion-channel gating. The mechanistic account considers thermal action unlikely for its cited low-heating pulses. Higher intensities can damage or ablate tissue.
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