Ultrasound Thermometry Using Echo Stretching for Microwave Hyperthermia.IEEE Trans Biomed Eng 2026 May 05; PP. [Online ahead of print]IT
This study presents an echo-stretching-based ultrasound technique for estimating temperature rise during hyperthermia therapy, eliminating the need for low-pass filtering and gradient computation used in conventional methods. The algorithm was evaluated using multiphysics simulations for thermal gradient of 0-0.1 °C using consecutive frames, and 0-6 °C using initial frame as reference. Inadequate up-sampling of radio frequency (RF) beamformed data resulted in spikes in the temperature estimates on echo stretching, which was reduced using adaptive up-sampling and median filtering. The average temperature estimation error relative to the peak temperature rise was less than 5% for 6 °C temperature gradient using 10λ sliding window, where, λ is the wavelength of ultrasound excitation in soft tissue. Window length of 40λ could resolve temperature gradient < 0.1 °C at the cost of spatial resolution. Axial resolution of 2.5 to 5 mm was achieved in hyperthermia temperature rise of 6 °C. Temperature estimation deteriorated with decline in signal to noise ratio (SNR) and depth. Experimental verification of echo stretching algorithm is tissue mimicking phantom and ex-vivo bovine tissues subjected to microwave hyperthermia at 434 MHz for 6 minutes using water loaded microstrip patch antenna indicated estimation error < 5 and 20% in phantoms and heterogeneous ex-vivo tissues, respectively. It is concluded that temperature rise estimated using the echo stretching of ultrasound RF data could be used for microwave hyperthermia treatment monitoring.
