Method and apparatus for improving contrast-to-tissue ratio in ultrasound contrast imaging with subharmonic imaging

A method for imaging a patient using diagnostic ultrasound, comprising:

• generating first and second signals having first and second frequencies, respectively, said second frequency being a subharmonic frequency with respect to said first frequency;
• combining said first and second signals to create a first transmit pulse;
• generating third and fourth signals with said first and second frequencies, respectively, said third and fourth signals being phase inverted with respect to said first and second signals;
• and
• combining said third and fourth signals to create a second transmit pulse.

A system for improving a contrast-to-tissue ratio while imaging contrast infused tissue and blood vessels, the system comprising:

• a seeded waveform generator generating first and second transmit pulses comprising basic and seed signals combined with one another for each of said first and second transmit pulses, said basic signal having a first frequency, said seed signal having a second frequency, said second frequency being a subharmonic frequency of said first frequency, said first and second transmit pulses being phase inverted with respect to each other;
• a transmitter transmitting said first and second transmit pulses into a patient having tissue and blood vessels infused with contrast agent, said contrast agent comprising microbubbles;
• a receiver receiving first and second sets of echoes based on said first and second transmit pulses, respectively;
• and
• a filter having said second frequency, said filter filtering said first and second sets of echoes to create filtered signals representing a response from said microbubbles.