Shear waves elastography is a technique designed to overcome some of the
disadvantages of other elastographic techniques. It is based on supersonic share
imaging, an ultrasound-based technique used for real-time visualization of soft tissue
viscoelastic properties. This technique is based on the combination of a radiation force
induced into the tissues by focused ultrasonic beams and a very high frame rate
ultrasound imaging sequence able to capture in real time the transient propagation of
the resulting shear waves. Shear waves’ propagation induces small tissue displacements
which are recorded by the imaging system, and measured using tissue Doppler
techniques. 2D-SWE offers as major innovations the ability to measure area and
distance ratios, a high spatial resolution and real-time capabilities. The technique
produces an image where true local tissue elasticity is displayed in a color map in “real
time”. Elasticity is displayed using a color coded image superimposed on a B-mode
image. The true elasticity is assessed based on Shear Waves propagation speed into the
tissue. Thus the technique permits a quantitative mapping of liver tissue viscoelasticity.
The technique was first available on the Aixplorer® system (SuperSonic Imagine,
France) and initially was used for the evaluation of breast nodules, of prostate
elasticity, for the evaluation of muscle and tendon stiffness and for thyroid disease
diagnosis. Published data showed a real value of this method for liver stiffness
estimation in patients with chronic hepatitis. It has the advantage that it can be also
used in patients with ascites. A similar technique is now available on the Logiq E9
system (General Electric) with promising results.
Keywords: Liver stiffness, Shear waves elastography, Viscoelasticity.
