Elastography is a medical imaging modality that maps the elastic properties of soft tissue. This modality emerged in the last decade. It includes Ultrasound Elasticity Imaging, Magnetic Resonance Elasticity Imaging and Tactile Imaging.
Ultrasound Elasticity Imaging
The Ultrasound Elasticity Imaging can be subdivided into strain and shear wave Elasticity Imaging.
Transient elastography is a 1D medical imaging modality based on mechanical tissue excitation and ultrasound measurements. Transient elastography uses a special probe that consists of an ultrasound transducer array mounted on the axis of a motor vibrator. The vibrator generates shear wave within the tissue, which is detected by pulse-wave ultrasound imaging in a manner similar to M-mode Doppler imaging. It is used for liver assessment, for example, to diagnose cirrhosis.
Ultrasound Elasticity Imaging is used for breast examination with a number of high-resolution linear transducers. A large multi-center breast imaging study has demonstrated both reproducibility  and significant improvement in the classification of breast lesions when shear wave elastography images are added to the interpretation of standard B-mode and Color mode ultrasound images.
Acoustic Radiation Force
Acoustic Radiation Force Impulse (ARFI) Imaging is another imaging modality being researched to non-invasively characterize liver stiffness. The key difference from transient elastography is that ARFI makes use of ultrasound beams to push the target tissue (called pushing beams), in additional to the conventional ultrasound beams for imaging (called tracking beams). 
Supersonic Shear Imaging
SuperSonic Imagine Real-Time ShearWave(TM) Elastography has demonstrated clinical benefit in breast, thyroid, liver, prostate and MSK imaging.
Magnetic Resonance Elasticity Imaging
Tactile Imaging is a medical imaging modality that translates the sense of touch into a digital image. Tactile Imaging is used for imaging of the prostate, breast, vagina and pelvic floor support structures, and myofascial trigger points in muscle.
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