Key result
Transcranial HIFU for ischemic stroke proves feasible at 1.1-1.5 MHz but requires higher element counts.
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High intensity focused ultrasound (HIFU) is capable of mechanically disintegrating blood clots at high pressures. Safe thrombolysis may require frequencies higher than those currently utilized by transcranial HIFU. Since the attenuation and focal distortion of ultrasound in bone increases at higher frequencies, resulting focal pressures are diminished. This study investigated the feasibility of using transcranial HIFU for the non-invasive treatment of ischemic stroke. The use of large aperture, 1.1-1.5 MHz phased arrays in targeting four clinically relevant vessel locations was simulated. Resulting focal sizes decreased with frequency, producing a maximum -3 dB depth of field and lateral width of 2.0 and 1.2 mm, respectively. Mean focal gains above an order of magnitude were observed in three of four targets and transducer intensities required to achieve thrombolysis were determined. Required transducer element counts are about an order of magnitude higher than what currently exists and so, although technically feasible, new arrays would need to be developed to realize this as a treatment modality for stroke.
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Pajek et al. (2012) studied Ischemic stroke. Transcranial high intensity focused ultrasound (HIFU) using 1.1-1.5 MHz phased arrays was evaluated on Feasibility, focal sizes, and mean focal gains at four clinically relevant vessel locations. Transcranial HIFU for ischemic stroke using 1.1-1.5 MHz phased arrays is technically feasible and achieves adequate focal gains, but requires the development of new arrays with higher element counts.
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