Stanford Advisors


All Publications


  • Increasing the transmission efficiency of transcranial ultrasound using a dual-mode conversion technique based on Lamb waves. The Journal of the Acoustical Society of America Kang, K. C., Kim, Y. H., Kim, J. N., Kabir, M., Zhang, Y., Ghanouni, P., Park, K. K., Firouzi, K., Khuri-Yakub, B. T. 2022; 151 (3): 2159

    Abstract

    Transcranial focused ultrasound (FUS) is a noninvasive treatment for brain tumors and neuromodulation. Based on normal incidence, conventional FUS techniques use a focused or an array of ultrasonic transducers to overcome the attenuation and absorption of ultrasound in the skull; however, this remains the main limitation of using FUS. A dual-mode conversion technique based on Lamb waves is proposed to achieve high transmission efficiency. This concept was validated using the finite element analysis (FEA) and experiments based on changes in the incident angle. Aluminum, plexiglass, and a human skull were used as materials with different attenuations. The transmission loss was calculated for each material, and the results were compared with the reflectance function of the Lamb waves. Oblique incidence based on dual-mode conversion exhibited a better transmission efficiency than that of a normal incidence for all of the specimens. The total transmission losses for the materials were 13.7, 15.46, and 3.91dB less than those associated with the normal incidence. A wedge transducer was designed and fabricated to implement the proposed method. The results demonstrated the potential applicability of the dual-mode conversion technique for the human skull.

    View details for DOI 10.1121/10.0009849

    View details for PubMedID 35364946

  • Patterned Interference Radiation Force for Transcranial Neuromodulation. Ultrasound in medicine & biology Kim, Y. H., Kang, K. C., Kim, J. N., Pai, C. N., Zhang, Y., Ghanouni, P., Park, K. K., Firouzi, K., Khuri-Yakub, B. T. 1800

    Abstract

    Compared with the conventional method of transcranial focused ultrasound stimulation using a single transducer or a focused beam, the compression and tensile forces are generated from the high-pressure gradient of a standing wave that can generate increased stimulation. We experimentally verified a neuromodulation system using patterned interference radiation force (PIRF) and propose a method for obtaining the magnitude of the radiation force, which is considered the main factor influencing ultrasound neuromodulation. The radiation forces generated using a single focused transducer and a standing wave created via two focused transducers were compared using simulations. Radiation force was calculated based on the relationship between the acoustic pressure, radiation force and time-averaged second-order pressure obtained using an acoustic streaming simulation. The presence of the radiation force was verified by measuring the time-averaged second-order pressure generated due to the radiation force, by using a glass tube.

    View details for DOI 10.1016/j.ultrasmedbio.2021.11.006

    View details for PubMedID 34955292