Average dose absorbed by biological specimens in a diffuse ultrasonic exposure field

A reverberation method has been investigated for determining the total acoustic energy absorbed by biological specimens exposed to ultrasound at clinical frequencies. The specimen is exposed to a diffuse ultrasonic field created in a small water‐filled tank by a 1.0‐MHz carrier signal, frequency modulated with white noise. Measurements of the total acoustic input power and the decay rate, both with and without the specimen, are used to determine average dose. Three different methods for measuring input power and one method for measuring decay rate have been investigated. Numerous performance tests have been used to assign uncertainty limits for the measurement of average dose. This new reverberation exposure method has been compared to the more traditional free‐field exposure method by recording the temperature rise within anesthetized mice for both methods. These results will be used to estimate the exposure conditions for each method needed to produce the same average temperature rise within an animal.