Water is filled in a receptacle, and an ultrasonic-wave transmitting flexible membrane is attached to the receptacle in a watertight manner. An ultrasonic probe is provided in the receptacle for mechanical scanning. The receptacle is coupled with a pipe through which the water in the receptacle can circulate....http://www.google.es/patents/US4681120?utm_source=gb-gplus-sharePatente US4681120 - Ultrasonic diagnosing apparatus
