Ultrasonic temperature monitoring in tissue phantoms by locally resolved measurement of longitudinal and transverse wave speed

Abstract

To optimize hyperthermia in cancer therapy, a monitoring of temperature and tissue properties inside the tumor and in the surrounding tissue is necessary during the therapy. As the use of computed tomography (CT) or Magnetic resonance imaging (MRI) during the operation is very expensive, ultrasonic measurements are a very good alternative.This contribution presents a method to measure the longitudinal wave speed spatially resolved by analyzing the ultrasonic signals reflected from small scatterers in a tissue phantom. Thus no additional reflectors at known positions are necessary. The measurements are carried out using a 10 MHz prefocused annular-array and the recorded signals are focused synthetically. Measurements are carried out on a tissue phantom synthesized by polyacrylamide. Algae are added to gain natural scattering in the phantom. The capabilities of the method are demonstrated by monitoring the temperature distribution during local heating of a phantom. Additionally, the reachable accuracy as well as reachable temporal and local resolution are discussed. Due to increasing heat supply denaturation occurs, a second measurand is necessary. Therefore, the transverse wave speed is determined by transient elastography.To optimize hyperthermia in cancer therapy, a monitoring of temperature and tissue properties inside the tumor and in the surrounding tissue is necessary during the therapy. As the use of computed tomography (CT) or Magnetic resonance imaging (MRI) during the operation is very expensive, ultrasonic measurements are a very good alternative.This contribution presents a method to measure the longitudinal wave speed spatially resolved by analyzing the ultrasonic signals reflected from small scatterers in a tissue phantom. Thus no additional reflectors at known positions are necessary. The measurements are carried out using a 10 MHz prefocused annular-array and the recorded signals are focused synthetically. Measurements are carried out on a tissue phantom synthesized by polyacrylamide. Algae are added to gain natural scattering in the phantom. The capabilities of the method are demonstrated by monitoring the temperature distribution during local heating of a phantom. Additionally, the reachable accuracy as we...