Ultrasound elastography: a new modality in routine practice.

t a fi d T t p n r r l fi w N of Diagnostic and Interventional Imaging, to an emerging technique: ultrasound elastography. This issue provides the readers with information necessary to understand this new modality on the eve of its clinical expansion. Analogies with the development of pulsed wave and color Doppler modes are important, especially for techniques providing two-dimensional color-coded elasticity maps in real time in a window superimposed on a B-mode image. As for Doppler, this new mode, ultrasound elastography, can be activated by pressing a single control on the ultrasound diagnostic imaging device. One dimensional shear wave elastography allows tissue stiffness measurements in a small region-of-interest that can be moved on a Bmode image, with quantitative measurements in kPa (pulsed wave Doppler allowing velocity measurements obtained from the Doppler gate moved on the B-mode image). Quasistatic elastography (qualitative) or shear wave elastography (quantitative) also allows tissue stiffness evaluation in a region-of-interest with a color map. While the displayed frame rates of real-time shear wave based techniques are still low (about 1 Hz), it compares with those of color Doppler imaging in its infancy. On this two-dimensional map, one can position a measuring region-of-interest, which provides quantitative information: it is the equivalent of pulsed Doppler mode. As for color Doppler, elastography imaging principles may seem complicated, but didn’t we say in the 1990’s that Doppler should be doomed to research university department only due to an increased examination time and to its complexity of implementation and interpretation? However, the difference that remains today between these two techniques is their level of clinical impact. For Doppler, the ability to have hemodynamic information was obviously sufficient. For elastography, several steps remain, which are linked to multiple factors: the diversity of existing techniques that do not produce similar results (qualitative, h t O