Magnetic resonance elastography (MRE) is a non-invasive medical imaging technique that measures the mechanical properties (stiffness) of soft tissues by introducing shear waves and imaging their propagation using MRI. Diseased tissues are often stiffer than the surrounding normal tissue. For instance, breast cancers are much harder than healthy fibroglandular tissue. This characteristic has been used by physicians for screening and diagnosis of many diseases, through palpation. MRE calculates the mechanical parameter as elicited by palpation, in a non-invasive and objective way.
Magnetic resonance elastography works by using an additional gradient waveform in the pulse sequence to sensitize the MRI scan to shear waves in the tissue. The shear waves are generated by an electro-mechanical transducer on the surface of the skin. Both the mechanical excitation and the motion sensitizing gradient are at the same frequency. This encodes the amplitude of the shear wave in the tissue in the phase of the MRI image. An algorithm can be used to extract a quantitative measure of tissue stiffness from the MRI in an elastogram.
Magnetic resonance elastography was first introduced by Muthupillai et al. in 1995 and is being investigated to be used for a multitude of diseases that affect the tissue stiffness. It has been used clinically for the assessment of liver fibrosis.
Liver fibrosis is a common result of many chronic liver diseases and if progressive leads to cirrhosis. Magnetic Resonance Elastography of the liver provides quantitative maps of tissue stiffness over large regions of the liver. This non-invasive technique is able to detect increased stiffness of the liver parenchyma, which is a direct consequence of liver fibrosis. It helps to stage liver fibrosis or diagnose mild fibrosis with reasonable accuracy.
Magnetic Resonance Elastography of the brain was first presented in the early 2000s and its measures have been correlated with memory tasks, fitness measures and various neurodegenerative conditions: Alzheimer’s Disease and Multiple Sclerosis to name a few. It has been found that as the brain ages, it loses its viscoelastic integrity due to degeneration of neurons and oligodendrocytes.
Brain MRE has only just begun for use in adolescents, and it shows potential towards understand adolescent pathology, recently it has found that adolescents have regionally different brain viscoelasticity than adults.
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