An ultrasound method and system are provided for producing three dimensional images. During an imaging session, a transducer, in response to a transmit beamformer, transmits ultrasonic energy at a first frequency band into a subject. The subject may be kept free of added ultrasound contrast agent throughout...http://www.google.de/patents/US5924991?utm_source=gb-gplus-sharePatent US5924991 - Ultrasonic system and method for harmonic imaging in three dimensions
