Shear wave elastography is a new 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
Ultrafast™ imaging system, and measured using tissue Doppler techniques. 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 wave
propagation speed into the tissue. Thus the technique permits a quantitative mapping of
liver tissue viscoelasticity.
The technique is 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. Preliminary
results showed a real value of this method for liver stiffness estimation in patients with
chronic hepatitis.
Keywords: Shear wave elastography, liver stiffness, viscoelasticity.