| 摘要 |
A system for the inspection of the internal nature of a material utilizes an exciting ultrasonic field which is directed at a focal point to be inspected and heats that focal point. An ultrasonic sensing beam is directed through the material and through the heated focal point and is received by a transducer. A differential measurement of a propagation parameter of the sensing beam is accomplished by comparing a burst of its ultrasonic waves through the focal point without the heating effect of the exciting field, with an identical burst of the same duration, amplitude and frequency, but immediately after the heating effect has been accomplished by the exciting field. This system may be used to determine tissue characteristics, internal blood flow, and for other medical diagnostic functions.
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