Transcranial Ultrasound Using Leaky Lamb Waves by Wedge Transducer Array

The transcranial ultrasound technique has been researched as a non-invasive method for the treatment of brain tumors, neuromodulation, and the delivery of cancer therapeutics. Focused ultrasound is one of the most common methods for noninvasive treatments, but the present technology generally uses an array of transducers of normal incidence. The general focused ultrasound technique has high transmission loss and heating of the skull because of the normal incidence. In this study, we present the design, analysis, and implementation of a wedge transducer array consisting of piezoelectric (PZT) ceramic elements for the dual-mode conversion technique, which means that the longitudinal wave in the wedge is converted to the Lamb wave in the skull and the Lamb wave is converted to the longitudinal wave in the brain. This technique enables efficient transmission, reduces heating of the skull, and extends the focal spot range. We fabricated the partial wedge transducer and conducted the experiments to calculate the total transmission loss of this system.