The propagation speed of a shear wave can be proven to be proportional to the Young's Modulus of tissue. A Shear wave is generated by an Acoustic Radiation Force Push (ARFI) which is generated at a point by transmitting focused to that point for several hundred microseconds. This will cause the tissue to move away from the transducer a few microns. When the transmission ends the tissue will return to its original position but in doing so in the non critically damped conditions it will overshoot and then osculate several times before coming to rest. The osculation will propagate at right angles to the transmitting vector as a shear wave. The characteristics of this shear wave are that its speed of propagation is between one and ten meters per second (proportional to the modulus of the tissue it passes through) it has a lower attenuation than the compression waves used to image in ultrasound. By creating B-Mode acoustic lines and examining the shear wave as it passes at several positions an estimate of the shear waves propagation speed or the modulus of the tissue may be estimated.
The display below is of the UltraVision estimating the modulus in a green box positioned by the user. The FDA approval for this mode and the shear imaging mode has not been submitted to the FDA for a 510K qualification at this time and so is not available in the Clinical system at this time.
UltraVision Corporation: 11770 US Highway 1, Suite 302E, Palm Beach Gardens, Florida, 33408-3054 Tel: (561) 626-4405 Info@winprobe.com
UltraVision Corporation is an accredited ISO13485:2003 / ISO 9001: 2008 manufacturer of medical ultrasound systems