Ultrasound imaging system for high resolution wideband harmonic imaging

An ultrasound system for producing high resolution wideband harmonic images comprising:

• an ultrasound probe comprising an array transducer adapted to transmit ultrasound beams and receive echo signals from along directions of transmitted ultrasound beams;
• a transmitter, coupled to the ultrasound probe, and adapted to control the probe to transmit first and second differently modulated transmit waveforms in a common beam direction, each waveform comprising two major frequency components;
• a buffer adapted to store echo signals received in response to transmission of at least the first transmit waveform;
• a summer coupled to the buffer and adapted to additively combine echo signals on a spatial basis which are received in response to transmission of the first and second transmit waveforms;
• a subtractor coupled to the buffer and adapted to subtractively combine echo signals on a spatial basis which are received in response to transmission of the first and second transmit waveforms;
• wherein the summer is further adapted to produce nonlinear echo signal components at an output and the subtractor is further adapted to produce linear echo signal components at an output;
• and further comprising:
• a first time-varying filter coupled to an output of the summer and adapted to vary from a high pass filter characteristic to a lower band filter characteristic as nonlinear echo signals are received from increasing depths;
• and a second time-varying filter coupled to an output of the subtractor and adapted to vary from a high pass filter characteristic to a lower band filter characteristic as linear echo signals are received from increasing depths;
• and an image processor adapted to produce an ultrasound image, and characterized in that:
• the summer and the subtractor are further adapted to produce four different major frequency components, each of which is either a fundamental frequency component, a harmonic frequency component, a sum frequency component, or a difference frequency components, and all of which are below the major frequency of the second harmonic component of the transmit waveform of the highest frequency.