A phased array antenna for simultaneous thermotherapy and sonography

The application of ultrasound for therapeutical treatment necessitates the control of the surgery process by means of an imaging system. A new type of linear phased array antenna, which is capable to generate high power therapy sound and also exhibits a pulse echo mode for imaging, was presented previously (T. Sheljaskov et al., 1996). Meanwhile, utilizing finite element simulations, boundary element simulations and experiments on prototypes, this concept could be improved in respect to the power transfer efficiency in therapy mode and the pulse shape in sonography mode. The novel antenna consists of three sectors: two of them are used only for producing 1.7 MHz sine burst therapy ultrasound, and the third is used for both, 5.1 MHz pulse-echo imaging as well as generating therapy ultrasound. The multifunctional elements of this sector cause 1.4 dB sine burst intensity loss compared to the pure therapy elements of the other sectors, as well as 7.3 /spl lambda/ pulse length, corresponding to -20 dB ringdown time.