title: Development of a spherically focused phased array transducer for ultrasonic image-guided hyperthermia.
abstract: A 1.5 MHz prolate spheroidal therapeutic array with 128 circular elements was designed to accommodate standard imaging arrays for ultrasonic image-guided hyperthermia. The implementation of this dual-array system integrates real-time therapeutic and imaging functions with a single ultrasound system (Vantage 256, Verasonics). To facilitate applications involving small animal imaging and therapy the array was designed to have a beam depth of field smaller than 3.5 mm and to electronically steer over distances greater than 1 cm in both the axial and lateral directions. In order to achieve the required f number of 0.69, 1-3 piezocomposite modules were mated within the transducer housing. The performance of the prototype array was experimentally evaluated with excellent agreement with numerical simulation. A focal volume (2.70 mm (axial)  ×  0.65 mm (transverse)  ×  0.35 mm (transverse)) defined by the  -6 dB focal intensity was obtained to address the dimensions needed for small animal therapy. An electronic beam steering range defined by the  -3 dB focal peak intensity (17 mm (axial)  ×  14 mm (transverse)  ×  12 mm (transverse)) and  -8 dB lateral grating lobes (24 mm (axial)  ×  18 mm (transverse)  ×  16 mm (transverse)) was achieved. The combined testing of imaging and therapeutic functions confirmed well-controlled local heating generation and imaging in a tissue mimicking phantom. This dual-array implementation offers a practical means to achieve hyperthermia and ablation in small animal models and can be incorporated within protocols for ultrasound-mediated drug delivery.
authors.affiliation: Department of Biomedical Engineering, University of California, Davis, CA 95616-8686, USA.
authors.forename: Jingfei
authors.initials: J
authors.lastname: Liu
authors.forename: Josquin
authors.initials: J
authors.lastname: Foiret
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Stephens
authors.forename: Olivier
authors.initials: O
authors.lastname: Le Baron
authors.forename: Katherine W
authors.initials: KW
authors.lastname: Ferrara
mesh_terms: D000818:Animals; D004867:Equipment Design; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D013813:Therapy, Computer-Assisted / Q000379:methods*; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods