Effects of physical parameters on high temperature ultrasound hyperthermia

The purpose of this research was to investigate the feasibility of inducing perfusion independent, predictable therapeutic thermal dose using high power ultrasonic pulses. Computer simulations were used to study the effects of blood perfusion, tissue properties, transducer characteristics, and treatment geometry on the temperature elevation and thermal dose delivered by short ultrasonic pulses. Experiments were conducted in vitro and in vivo to investigate the effects of blood perfusion changes. Results show that short pulse lengths (less than or equal to 2 s) and small focal diameters (approximately 3 mm) give temperature elevations and thermal doses which are nearly perfusion independent. Normal fluctuations in tissue properties should not have a significant effect on the treatment provided that proper choice of transducer is made for each individual application.