DEVELOPMENT OF ULTRASONIC HYPERTHERMIA SYSTEM FOR MALIGNANT TUMOR IN SMALL ANIMALS

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Hyperthermia induced by ultrasound has been employed as a modality for cancer therapy because of the feasibility of penetration and focusing. Therefore, ultrasonic hyperthermia system for malignant tumor in small animals has been developed. This system consists of a ultrasonic generator, data accumulation system, temperature measurement system, a circulator with temperature controller and degassing system. This system has an applicator equipped with a non-focused ultrasound transducer or a focused one. Two dimensional temperature distributions for the phantom after heating were measured by using agar-graphite mixture phantom. Homogeneous heating pattern from 1 to 4 cm diameter with 2 cm depth was obtained when a frequency of 1.5 MHz was used. A chemical dosimeter utilizing the Weissler reaction (determination of iodine from potassium iodide due to ultrasonic cavitation) was improved with using trichloroacetic acid and the absorbed-dose distribution was estimated by using a "lattice" vessel consisting of 100 small containers. Enhancement of transdermal drug absorption by non-thermal effects of ultrasound has also been investigated.