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.

Combining activatable nanodelivery with immunotherapy in a murine breast cancer model

“…Hyperthermia was performed using a programmable US system combining imaging and therapy (Vantage 256, Verasonics, Kirkland, WA). A custom 128-element 1.5 MHz therapeutic array was used to heat the tumor [35]. Heating was performed with bursts of 2.5 MPa peak negative pressure, with a pulse repetition frequency of 100 Hz and burst duration ranging from 0 to 7 ms as controlled by a proportional integral derivative (PID) controller (duty cycle ranging from 0 to 0.7) set to maintain the tumor temperature at 42 °C.…”

Nonviral ultrasound-mediated gene delivery in small and large animal models

“…Use option A for small animal models (e.g., rodents) or in the case that the targeted area for gene delivery is superficial (<3 cm from the skin). This option requires the use of the Siemens Antares ultrasound system with a colinear array transducer or an equivalent multifrequency array and system, as well as a spacer (refer to Steps 1–5 for instructions on how to prepare the spacer) 34–36 . Use option B for large animal models (e.g., canine, feline, equine and bovine).…”

Acoustical structured illumination for super-resolution ultrasound imaging

“…This is achieved by controlling the phase and apodization of each individual transducer element, providing the method with the distinct advantage of being dynamic and reconfigured in real-time. In ultrasound, multi-foci patterns have been used previously to generate a uniform temperature field for hyperthermia treatments 14 – 16 , for ultrasonic neuro-modulation 17 , for the generation of acoustic holograms 18 , 19 , and for multiline cardiac imaging 20 , 21 . To our knowledge, they have not been used for ultrasound super-resolution imaging.…”