Determining material stiffness using multiple aperture ultrasound

An ultrasound imaging system, comprising:

• a multiple aperture ultrasound transducer array;
• a shear-wave-initiating transducer;
• and
• a processor configured to control the multiple aperture ultrasound transducer array to transmit a first circular waveform into a region of interest, receive echoes of the first circular waveform, and form a baseline image of the region of interest;
• the processor being further configured to:
• control the shear-wave-initiating transducer to transmit an ultrasonic pulse configured to induce a propagating shear wave in the region of interest;
• control the multiple aperture ultrasound transducer array to transmit a second circular waveform into the region of interest, receive echoes of the second circular waveform, and form a first image frame that includes a first speckle pattern caused by the propagating shear wave as it moves through the region of interest;
• control the multiple aperture ultrasound transducer array to transmit a third circular waveform into the region of interest, receive echoes of the third circular waveform, and form a second image frame that includes a second speckle pattern caused by the propagating shear wave as it moves through the region of interest;
• subtract the baseline image from the first image frame to obtain a first difference frame;
• subtract the baseline image from the second image frame with the electronic controller to obtain a second difference frame;
• calculate a first distance between an init line of the multiple aperture ultrasound transducer array and the first speckle pattern of the first difference frame to determine a first position of the propagating shear wave;
• calculate a second distance between the init line of the multiple aperture ultrasound transducer array and the second speckle pattern of the second difference frame to determine a second position of the propagating shear wave;
• and
• calculate a propagation speed of the propagating shear wave in the region of interest from the first and second positions in the first and second difference frames.