A 64-Element Phased Array System for Transcranial Ultrasound Delivery in Small Animal Models

Saba Rahimi (1,2), Kullervo Hynynen (1,2,3)

  1. Institute of Biomaterials & Biomedical Engineering (IBBME), University of Toronto

  2. Physical Sciences Platform, Sunnybrook Research Institute, Toronto, ON, Canada

  3. Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada

There has been long standing interest in using noninvasive focused ultrasound (FUS) to precisely target selective regions in rodent brain without further damage or exposure to surrounding and vital brain tissues. The use of high frequency ultrasound is one potential approach for generating small focal volumes and thus target smaller brain features. In this paper we present the design, fabrication, and characterization of a 64-element 3.3 MHz phased array for pre-clinical FUS experiments. Designed to focus at 15-mm depth and 10-V peak-to-peak AC excitation, the peak negative pressure was measured 2.45 MPa, which is expected to open the blood-brain barrier (BBB). The following ex-vivo experiments successfully demonstrated the array’s capability to reconstruct the focus. The rat skull attenuated, distorted and destroyed the field; however, a sharp focal spot was created by phase corrections. In summary, the results showed that transcranial delivery of therapeutic ultrasound with small focal spots is feasible. 

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