Noninvasive temperature measurement during High Intensity Focused Utrasound (HIFU) treatments; What are the problems, and is it really necessary?

Gail ter Haar , Victoria Bull , John Civale , Ian Rivens

Real-time measurement of temperature is the holy grail of HIFU treatment monitoring as it allows calculation of the delivered thermal dose, an indicator of successful ablation. Much HIFU treatment monitoring research concentrates on improving MR and ultrasound thermometry, although many factors fundamentally limit measurement accuracy for both modalities. Temporal and volumetric averaging of highly localised rapid heating can underestimate peak temperatures. In MR, any attempt to improve temporal or spatial resolution results in lower contrast and compromises temperature resolution. While US imaging offers higher temporal resolution, the relatively low signal to noise ratio is problematic. In both cases, cavitation can significantly impair measurement. In MR thermometry, temperature resolution depends on accurate knowledge of the proton resonance frequency coefficient. Whilst this is easily obtained for water, measurement in tissue is harder. Current ultrasound guided clinical HIFU treatments rely on visualising bubbles created in tissue. Ultrasound thermometry requires accurate knowledge of the temperature dependent speed of sound for the tissue, which is known to be highly variable. Given these confounding factors, it is questionable as to whether it is really temperature we require, or whether improvements in the ability to detect coagulation in tissue might lead to greater success in ablative therapies.

Mots clés: Therapeutic ultrasound; HIFU

Domaines: Acoustique [physics.class-ph]

Gail ter Haar, Victoria Bull, John Civale, Ian Rivens. Noninvasive temperature measurement during High Intensity Focused Utrasound (HIFU) treatments; What are the problems, and is it really necessary?. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00810936⟩