Optimal configuration of multiple-focused ultrasound transducers for external hyperthermia

External ultrasound hyperthermia is considered to be a very flexible modali ty for heating deep-seated tumors owing to its penetration and focusing abi lity, However, using this flexibility requires that many complicated, inter acting decisions be made to obtain optimal treatment. This paper presents t he feasibility of arranging multiple-focused ultrasound transducers to prod uce an appropriate heating pattern for a specific treatment, based on the o ptimal scan parameters obtained from an optimization algorithm. The variabl e scan parameters of the heating system optimized are the transducer tilt a nd rotation angles, focal depth, scan radius, and output acoustical power. After obtaining the optimal scan parameters, multiple transducers are syste matically arranged according to these scan parameters. Three-dimensional ul trasound power deposition and temperature distribution for a specific treat ment are calculated for this multiple ultrasound transducer system. A more uniform temperature distribution in the treatment region for a large, highl y perfused tumor can be achieved by scanning the system with respect to the central scan axis and/or swinging the transducers inwards and outwards. Th e maximum heating depth of focused ultrasound transducers used in this heat ing system is also studied. Simulation results demonstrate that the optimal arrangement of this multiple-focused ultrasound transducer system is highl y promising for heating deep, large, and highly perfused tumors. (C) 1999 A merican Association of Physicists in Medicine. [S0094-2405(99)02109-4].