Figure 1.

Technique and principles of ultrasound elastography. A. The technologies currently used and commercially available in ultrasound [US] machines are divided into two main types: strain [SE] and shear wave elastography [SWE]. In SE, the induced tissue displacement is traced between pairs of echo frames, then the strain is calculated from their gradient. Technically, two SWE methods can be distinguished: the point-SWE [pSWE] and the 2-dimensional-SWE [2D-SWE]. In the p-SWE, the speed of shear wave is measured in a single specific location [ROI]; the 2D-SWE produces a quantified colour map of the distribution of shear wave velocities in a wider region. B. An example of SE applied to bowel wall is shown. SWE: shear wave elastography.