Combined ultrasound image guidance and therapy using a therapeutic phased array

Ultrasonic imaging has been suggested for guidance of high intensity focused ultrasound therapy (HIFU). This is typically implemented using two different ultrasonic transducer systems. However the need for two transducers may pose practical difficulties such as alignment and different coordinate systems. In this paper we investigate the possibility of using the same physical transducer array for performing both therapy and imaging. A spherically shaped 1-D 64-element high intensity focused ultrasound transducer capable of operating in therapeutic and imaging modes was designed and fabricated. In vitro experiments were conducted to show that this transducer is capable of creating well defined lesions 30-50 mm deep into bovine muscle samples. Furthermore, an experimental pulse-echo system was designed to collect full synthetic aperture data using this transducer. Images of multiple-wire and speckle-generating phantoms are shown to illustrate the imaging capability of this transducer. Although the image quality achieved with this array is inferior to that obtained by conventional diagnostic imaging transducers, it is sufficiently high to produce image features suitable for guidance.