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Design and evaluation of broadband multi-channel ultrasound driving system for large scale therapeutic phased arrays

Therapeutic ultrasound phased arrays show great promise in the treatment of brain disorders and deep-seated tumors where precise beam steering and controlled power deposition are needed as stated in D. Daum et al. (1999) and G.T. Clement et al. (2000). In addition, cavitation and mechanical effects, which are fast becoming essential elements of these therapies, could potentially be better controlled with phased array systems that employ multi-frequency techniques according to S. Umemura and K. Kawabata (1996) and J.Y. Chapelon et al. (1996). However, these recent therapeutic ultrasound applications increase the demands on the phased array hardware, both the ultrasound transducer and the multi-channel electronic driving system. First, large scale (greater than 200 elements) high-density (elements on the order of 1/2 or less), broadband ultrasound phased array transducers capable of generating high power fields are required. Second, multi-channel amplifier systems that are capable of fully utilizing these large-scale, high-density, broadband arrays need to be developed. With the advent of high power piezocomposites according to T.R. Shrout et al. (1980) and T.R. Gururaja et al. (1980) broadband high-density transducers are now available for therapy; however, the current driving system technology still falls short. In this paper, we describe the design, construction, and evaluation for a multi-channel broadband phased array amplifier system capable of driving large-scale therapeutic phased arrays.