WE‐B‐220‐01: Ultrasound‐Guided Techniques for HIFU Monitoring

Abstract

HIFU is the only truly noninvasive and non‐ionizing tumor treatment method. Unlike RF ablation, HIFU does not require interstitial tissue incision or needle insertion, but instead induces heat extracorporeally. Several methods have been developed for efficient HIFU monitoring. In ultrasound‐guided methods, the HIFU lesion can be detected when cavitation or boiling occurs due to the high bubble concentration that causes high echo amplitudes. Tissue coagulation also results in the increase of tissue attenuation, which has also been shown to efficiently map the lesion size when attenuation is estimated. Another technique that combines the resulting well known optical opacity of the resulting lesion and ultrasound is the opto‐acoustic technique that has been shown to determine the lesion formation. Finally, tissue coagulation has been associated with significant changes (2–10 times) in tissue stiffness. Elastography uses a small external compression in the detection of HIFU‐induced lesions after formation ex vivo. Harmonic Motion Imaging (HMI) uses a focused ultrasound (FUS) beam to generate an oscillatory acoustic radiation force for an internal, non‐ contact palpation to simultaneously internally estimate relative tissue stiffness and induce thermal damage. HMI has been shown to be successful in monitoring and assessing the formation of a lesion both ex vivo and in vivo.