Imaging of Tissue Elasticity in Gastrointestinal Disorders
Elastography or strain imaging are ultrasonographic methods which detect the elasticity or stiffness of a tissue providing a visual display. The basis of every strain imaging technique is to measure tissue deformation caused by an external stimulus. The derivative of the tissue displacement is called strain, and can be calculated by cross-correlating the radio-frequency data before and after compression. The strain value in each point is color-coded and displayed in an elastogram. This elastogram can then be combined with the B-mode image to display the elastic properties of the tissue to the examiner through color information. Equipment using a quasi-static method of producing strain in the tissue through external compression with the US probe is now commercially available for clinical application. The quasi-static application of elastography of the small intestine represents special difficulties, as the pressure from the US transducer can cause several changes. When adding pressure, one not only deforms the GI wall, but also displaces the luminal content and the intestine itself. With refined technology and adapted transducers, sonoelastography may become an important imaging modality to supplement B-mode ultrasonography for the assessment of gastrointestinal diseases.
KeywordsStrain Ratio Transient Elastography Strain Imaging Shear Wave Speed Elasticity Imaging
We thank Dr. Jo Erling R. Waage for allowing us to include the images of Endorectal utrasound scanning with real-Time Elastography.
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