Study of fast temperature estimation during hyperthermia using ultrasound digital images

Abstract

The temperature change estimation method is based on the thermal dependence of the ultrasound speed and the thermal expansion of the medium. Local changes in the speed of sound due to change in the temperature produce apparent displacements of the scatterers. In our study a new technique is proposed in which the axial physical displacements are obtained form digital ultrasound images. The axial speckle pattern displacement is determined using a cross-correlation algorithm. The displacement data is then used for computing the temperature changes. Experiments are performed on tissue mimicking (TM) phantoms. The temperature changes during heating are measured invasively by NTC thermistors. There is good agreement between ultrasonic temperature estimations and invasive temperature measurements. The average error is 0.2degC, the maximum error is 0.53degC, and the standard deviation is 0.19degC. It is proven that, the proposed algorithm is capable of extracting the temperature information from ultrasound digital images with high accuracy.