A theoretical and experimental study of the feasibility of high temperature ultrasound hyperthermia

Abstract

The purpose of this research was to investigate the feasibility of using high temperature ultrasonic pulses to administer therapeutic hyperthermia treatments independent of changes in blood perfusion and tissue properties. The use of a computer simulation program was 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 high temperature ultrasonic pulses. Experiments were conducted in vitro and in vivo to investigate the effects of blood perfusion changes. Other experiments were carried out in dog thigh muscle to determine the effects of changes in tissue properties. A final study was done where murine melanoma in mice were treated with high temperature ultrasound. Results show that shorter pulse lengths (≤ 2 s) and smaller focal diameters (≤ 3 mm) give practically perfusion independent temperature elevation and thermal dose. 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. High temperature ultrasonic pulses have also been shown to induce tumor responses. Based on this research, this technique is a feasible means of administering hyperthermia for cancer therapy.