On the design of dual mode arrays for imaging and therapy

Dual Mode Ultrasound Arrays (DMUAs) represent a new paradigm in non-invasive image-guided surgery, offering the unique advantage of inherent registration between the imaging and therapeutic coordinate systems. Furthermore, complete synchronization between the imaging and therapy hardware allows real-time monitoring of tissue changes on a millisecond timescale. The sensitivity of diagnostic pulse-echo ultrasound to HIFU-induced tissue changes has been established. Currently, disparate requirements of imaging and therapeutic piezo-elements present an obstacle to DMUA implementation. High performance imaging requires wide bandwidth, yet most therapeutic piezo-elements are based on narrowband ceramic technology due to its high electro-mechanical coupling. In the current study, we describe a 5-step design approach for image-guided HIFU systems. DMUA prototypes will be optimized for therapeutic performance using continuous wave (CW) simulation tools. Once satisfactory performance in the therapeutic operating field (ThxOF) has been achieved, piezo-element bandwidth will be increased until imaging performance meets specifications in the imaging field of view (IxFOV). Therapeutic performance is quantified based on intensity (focusing) gain throughout the ThxOF, while imaging performance is assessed based on axial resolution in the IxFOV. In addition, a new 4-MHz cylindrical array design prototype will be presented.