Arrays of multielement ultrasound applicators for interstitial hyperthermia

Arrays of multielement ultrasound applicators for interstitial hyperthermia have been developed and tested both in vitro and in vivo. The system inclu des multielement applicators, a 64 channel RF driving unit, a power measuri ng unit, a 112 channel multisensor temperature measuring unit, and a water cooling unit. Ninety-five arras of single-element and nine arrays of three- element ultrasound applicators were designed, built, and characterized by m easuring transducer efficiency and ultrasound held distribution. Improved u niformity in the azimuthal direction was achieved by using multiple driving frequencies. In addition, production of ultrasound in a desired sector of the transducer was possible by selecting a suitable frequency. Both in vitro and in vivo experiments showed that 92% of monitored temperat ure points within the target volume of 30 mm x 30 mm x 35 mm achieved a the rapeutic temperature rise (above 5 degrees C) when an array of five three-e lement applicators were used. These results indicated that the arrays of mu ltielement ultrasound applicators hare distinct advantages over present int erstitial hyperthermia modalities in terms of the capability to control the temperature distribution with a large catheter spacing. ris a conclusion, the feasibility of a practical arrays of multielement ultrasound applicator s for interstitial hyperthermia was demonstrated.