Broadband dual-mode HIFU array for therapy monitoring and 3D target motion estimation

This project implements previously developed techniques for guiding and monitoring thermal HIFU therapy using imaging arrays with a spherically shaped therapeutic array for dual-mode operation. Three-dimensional motion tracking, thermal strain measurement, and radiation force rebound measurement within the HIFU steering volume are performed using only the therapy array. The techniques have typically been studied for conventional ultrasound imaging using linear, curvilinear, or phased arrays which are usually placed coaxially in the center of the HIFU array. While the dual-mode approach does not provide the image quality and wide field of view of an imaging array, the perfect co-registration of the therapy array, and its 3D view of the region of interest present a valuable opportunity for ultrasound-guided focused ultrasound (USgFUS) therapy systems. A family of Sonic Concepts broadband spherically-focused HIFU array transducers, driven with the Verasonics HIFU-configured ultrasound system, is used to assess real-time performance of the dual-mode approach, in simulation and experiment. Simulations using the Verasonics acquisition software with a set of point scatterers produce the RF backscatter data used by the monitoring algorithms. The particles are displaced in time using motions that mimic the true or apparent displacements of tissue-like media either in translation, heated by a HIFU focus, or deformed by a radiation force beam. Preliminary experiments using a 128-element HIFU array and a scattering hydrogel phantom indicate that the simulations are effective for studying a range of tradeoffs in transducer design and therapy monitoring approaches.