Real-time non-invasive control of tissue temperature using high-frequency ultrasonic backscattered energy

A real-time and non-invasive thermometry method is crucial for thermal therapies to monitor and control the treatment. Ultrasound can be used as an attractive thermometry modality for its relatively high sensitivity to change in temperature and fast data collection and processing abilities. In this work, an ultrasound thermometry method based on the change in backscattered energy (CBE) is used to control the tissue temperature using a closed-loop controller in real-time. A clinical high-frequency ultrasound scanner was used to acquire RF echo data from ex vivo porcine tissue samples while the tissue was being exposed to an interstitial laser heating source. The control system was used to rapidly increase the temperature from 37°C (baseline temperature) to 43 °C (target temperature) and maintain the target temperature for about 6 minutes. The results show that the ultrasound thermometry based on CBE generated by a high-frequency ultrasound scanner can be used to generate 2D temperature maps of a localized heating region in the hyperthermia temperature range (∼43°C). The estimated temperature varied by an average of ±0.8 °C compared to a calibrated fiber-optic measurement. Thus, a non-invasive ultrasound thermometry method based on the CBE technique can be used for real-time monitoring and control of hyperthermia treatments, using the interstitial laser heating source with acceptable accuracy.