Ultrasound Elastography for Biomedical Applications and Medicine

15 Dynamic Elasticity Imaging

Kevin J. Parker

Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY, USA

15.1 Vibration Amplitude Sonoelastography: Early Results

Vibration amplitude sonoelastography entails the application of a continuous low‐frequency vibration (40–1000 Hz) to excite internal shear waves within the tissue of interest [1, 2]. A disruption in the normal vibration patterns will result if a stiff inhomogeneity is present in soft tissue surroundings. A real‐time vibration image can be created by Doppler detection algorithms. Modal patterns can be created in certain organs with regular boundaries. The shear wave speed of sound in the tissue of these organs can be ascertained with the information revealed by these patterns [3].

Figure 15.1 reproduces the first vibration‐amplitude sonoelastography image [1, 2], which marked the emergence of elastography imaging from the previous studies of tissue motion. The vibration within a sponge and saline phantom containing a harder area (the dark region) is depicted by this low resolution image. Range‐gated Doppler was used to calculate the vibration amplitude of the interior of the phantom as it was vibrated from below. By 1990, a modified color Doppler instrument was used by the University of Rochester group to create real‐time vibration‐amplitude sonoelastography images. In these images, vibration above a certain threshold (in the 2 µm range) produced a saturated color (