Subject(s)
Dental Porcelain , Metal Ceramic Alloys , Technology, Dental/methods , Humans , Tooth, ArtificialABSTRACT
A system for applying local hyperthermia employing ultrasonic transducers with annular focusing lenses gave better temperature uniformity in small fibrosarcomas than conventional unfocused transducers. The lenses were designed for ultrasonic frequencies of 3, 4, 5 and 9 MHz for tumors approximately 6 mm dia. Tests in degassed water indicated that the focusing lenses concentrated approx. 80% of the ultrasonic energy into an annular-shaped focus of 6 mm dia. located at a distance of 3 cm in front of the lens. These transducers were used to heat subcutaneous PARA-7 fibrosarcomas in hamsters. Steady-state temperature measurements indicated temperature gradients within tumors of 0.5-1.0 degree C when transducers employing annular-focused lenses were used, versus gradients of 2.0-2.3 degree C with 10 mm dia. unfocused transducers.
Subject(s)
Fibrosarcoma/therapy , Hot Temperature/therapeutic use , Lenses , Soft Tissue Neoplasms/therapy , Ultrasonic Therapy/instrumentation , Animals , Cricetinae , Mesocricetus , Neoplasm Transplantation , Sarcoma, Experimental/therapy , TransducersABSTRACT
A minicomputer-based system was designed to control the microwave (2.45-GHz) power to four local hyperthermia applicators. Errors in temperature measurement, due to electromagnetic field interactions with small thermocouple probes, are minimized by sampling the temperature only when the microwave power is off. The programmable controller can regulate the temperature in tumors in 0.1 degree C increments from 30 to 60 degrees C. This technique reduces temperature differences throughout the tumor at steady state to less than 0.4 degrees C and prevents skin burns.