Thermoacoustic Analysis of Cortical Bone Phantom by Ultrasonic Longitudinal Critically Refracted Waves

Ultrasound, a widely used technique in medical applications for its non-ionizing properties, low cost, and ease of handling, proves its practicality in hyperthermia. High-intensity focused ultrasound (HIFU) is a prime example, as it has been extensively employed to concentrate all its energy at a specific point with millimetric precision. When used in conjunction with other treatment techniques, HIFU can alleviate the pain caused by cancer, thus improving the quality of life for patients with bone metastases. However, monitoring the temperature rising at the target remains a challenge. Here, we propose a new method supported by ultrasonic longitudinal critically refracted (LCR) waves to estimate the temperature at the soft tissue and bone boundary. We tested our model using polymethylmethacrylate (PMMA) to mimic cortical bone tissue. We can monitor the temperature in real-time through ultrasonic waves, providing a practical solution to a longstanding challenge in hyperthermia treatment. The results showed that temperature strongly influences the speed of sound and the time of flight of the propagating wave. The work demonstrated the practical and straightforward use of the ultrasonic method to obtain material constants, which are essential in various fields.