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Efficient transcranial ultrasound delivery via excitation of Lamb waves

Transcranial focused ultrasound is being researched as a noninvasive means of ablating brain tumors and of increasing delivery of cancer therapeutics through the blood-brain barrier. However, the current techniques are implemented by means of a large-aperture spherical transducer. The geometric focus of these transducers limits the treatment envelope to the center of the brain, whereas the majority of cancers, especially metastases, occur along the periphery of the brain. In addition, these transducers create waves that impinge perpendicularly on the skull, which is inefficient. A normal incident transmission also sets up standing waves in the skull, which along with high attenuation leads to excess heating and a requirement for active cooling. We have developed an array of ultrasound wedge transducers capable of efficiently delivering focused ultrasound energy into the brain with minimal heating of the skull and the ability to address regions in the brain that are close to or far from the skull.