When a static or dynamic force is applied in a region of interest deformations of the structures are proportional to the mechanical impedance of the environment. For example, when the ultrasonic transducer is pressed over the region of interest, the length of the path to be traversed by the ultrasonic pulse is modified and time delays, after deformation, will be proportional to the stiffness of the media with different acoustic impedances. The image formed by the ratio between the deformation caused in the different tissues acoustic means and the force applied on them has been historically known elastography image or deformation. Elastography dynamic generally makes use of non-contact force, such as ultrasonic radiation force, magnetic force, among others, to produce a mechanical disturbance in the region of interest.
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