Development of a spherically focused phased array transducer for ultrasonic image-guided hyperthermia

• Published in: Physics in medicine & biology Vol. 61; no. 14; pp. 5275 - 5296
• Main Authors: Liu, Jingfei, Foiret, Josquin, Stephens, Douglas N, Le Baron, Olivier, Ferrara, Katherine W
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 21.07.2016
• Subjects: Animals; Equipment Design; focused ultrasound therapy; Humans; Hyperthermia, Induced - instrumentation; Hyperthermia, Induced - methods; Image Interpretation, Computer-Assisted; Models, Theoretical; Phantoms, Imaging; phased array transducer; Therapy, Computer-Assisted - methods; Transducers; ultrasonic image-guided hyperthermia; Ultrasonography - instrumentation; Ultrasonography - methods; ultrasound hyperthermia
• ISSN: 0031-9155; 1361-6560
• DOI: 10.1088/0031-9155/61/14/5275

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.