A linear phased array for prostate therapy

A linear phased array for thermotherapy of the prostate with rectal access has been developed. The curved transducer elements with a radius of curvature of 56 mm provide a prefocus in a first plane at a distance of 10 mm in the tissue. The 125 transducer elements can be steered to scan the tumor area in the other plane, while the first plane is being scanned by rotation of the array around its axis. The transmission efficiency of the transducer elements is 47% at 1.7 MHz with a -3 dB bandwidth of 100 kHz due to single matching layer and air backing. The low electrical cross-coupling (-30 dB) enables broad angle single element transmission with a -3 dB angle of more than 50/spl deg/. A simulation program incorporating the element's curvature and different fluids demonstrates the array electronic focusing property in one plane in conjunction with the mechanical prefocus in the other plane.