Attenuation mapping for monitoring thermal therapy using ultrasound transmission imaging

The use of an ultrasound (US) transmission imaging system to monitor attenuation changes during tissue heating was investigated. This. paper presents preliminary results of images obtained from an acoustic camera before, during and after heating tissue phantoms using a heated needle. Two types of tissue-mimiciking phantoms were used, agar and polyacrylamide-based. Regions of interests were chosen in images obtained from the real-time imaging system, and the pixel intensity values before, during and after heating were compared. In both phantoms, a decrease in image intensities was observed during heating, indicating an increase in tissue attenuation. Additionally, an irreversible change in image intensity was observed in regions close to the heat source. The reversibility of the intensity change was shown to be a function of the distance from the heating needle to the selected region. Initial results indicate that US transmission imaging can be used to monitor thermal therapy.