Ultrasound Thermometry Using Echo Stretching for Microwave Hyperthermia

Area of Science:

• Medical Physics
• Biomedical Engineering
• Ultrasound Imaging

Background:

• Hyperthermia therapy requires precise temperature monitoring.
• Conventional methods for temperature estimation have limitations, including the need for low-pass filtering and gradient computation.

Purpose of the Study:

• To develop and evaluate an echo-stretching-based ultrasound technique for estimating temperature rise during hyperthermia.
• To eliminate the need for conventional filtering and gradient computation in temperature estimation.

Main Methods:

• Utilized multiphysics simulations to evaluate the algorithm for thermal gradients from 0-0.1 °C and 0-6 °C.
• Employed adaptive up-sampling and median filtering to mitigate spikes in temperature estimates caused by inadequate RF data up-sampling.
• Validated the echo stretching algorithm using tissue-mimicking phantoms and ex-vivo bovine tissues subjected to microwave hyperthermia.

Main Results:

• Achieved average temperature estimation error less than 5% for a 6 °C temperature gradient using a 10λ sliding window.
• Demonstrated the ability to resolve temperature gradients below 0.1 °C with a 40λ window length, albeit with reduced spatial resolution.
• Attained an axial resolution of 2.5 to 5 mm for a 6 °C hyperthermia temperature rise.
• Experimental verification showed estimation errors below 5% in phantoms and 20% in heterogeneous ex-vivo tissues.

Conclusions:

• The echo-stretching ultrasound technique provides a viable method for estimating temperature rise in hyperthermia treatments.
• This technique can be effectively used for monitoring microwave hyperthermia therapy.
• The method shows promise for improving the precision and efficiency of thermal monitoring in clinical applications.