Evaluation of experimental methods for assessing safety for ultrasound radiation force elastography

¹ Department of Medical Physics and Bioengineering, Royal United Hospital, Bath BA1 3NG, UK
² Department of Clinical Measurement, Royal National Hospital for Rheumatic Diseases, Upper Borough Walls, Bath BA1 1RL, UK
³ Joint Department of Physics, Institute of Cancer Research and Royal Marsden Hospital NHS Trust, Sutton, Surrey SM2 5PT, UK
⁴ INSERM and Université de Lyon, U556, Lyon, F-69003, France

	Abstract

Standard test tools have been evaluated for the assessment of safety associated with a prototype transducer intended for a novel radiation force elastographic imaging system. In particular, safety has been evaluated by direct measurement of temperature rise, using a standard thermal test object, and detection of inertial cavitation from acoustic emission. These direct measurements have been compared with values of thermal index and mechanical index, calculated from acoustic measurements in water using standard formulae. It is concluded that measurements using a thermal test object can be an effective alternative to the calculation of thermal index for evaluating thermal hazard. Measurement of the threshold for cavitation was subject to considerable variability, and it is concluded that the mechanical index still remains the preferred standard means for assessing cavitation hazard.