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Biopsies, although invasive and unpleasant, are typically the best way to diagnose the health of human tissue, especially the liver. A group of researchers and physicians at the Mayo Clinic in Rochester, Minn., is hoping to change this through a relatively new approach known as magnetic resonance elastography (MRE), which they developed to measure the stiffness or elasticity of tissue and organs without the need for a scalpel.
Through MRE, a device placed on the body near the tissue being tested uses vibration to generate low frequency sound waves that pass through organs that have varying degrees of elasticity. These data are measured and analyzed to determine when tissue is stiffer than it should be, often a sign that it is unhealthy.
In addition to biopsies, doctors often make disease diagnoses by feeling the skin and tissue surrounding an organ with their fingers to determine the level of elasticity (a process called palpation). The goal with MRE is to eliminate the need for painful biopsies and offer a sort of virtual palpation that could even be used to examine organs including the heart and the brain, which doctors cannot reach without major surgery.
Thus far, the most common application of MRE since it was first used at the Mayo Clinic in 2007 has been diagnosing liver disease. The demand for a better way of diagnosing this disease is greater than most people think, says Richard Ehman, a Mayo Graduate School professor of radiology and leader of the Mayo Clinic team that developed MRE. Nearly 170 million people worldwide have hepatitis C infections and one quarter of those cases can lead to liver disease that leaves the organ scarred and otherwise damaged, he says, adding, "The latest estimate is that in the U.S. five million people have hepatitis C infections and many people don't even know it."
More than 15 years ago, Ehman began experimenting with mechanically produced seismic waves—called shear waves—that could travel through human tissue. As these waves pass through the body, they displace tissue by a matter of a micron or less. Ehman and his colleagues modified a magnetic resonance imaging (MRI) system to be able to detect these incredibly subtle changes and found that by applying a mathematical algorithm to the data produced by the scan researchers could generate an image that quantified the stiffness or elasticity of an organ. "I was inspired by the power of palpation as a diagnostic tool for physicians," he says. "Simple touch can find things that highly sophisticated equipment can miss."
It took the ensuing decade and a half to develop the technology that could make MRE practical in the human body. GE Healthcare on Monday introduced its MR-Touch device, the first commercial application of MRE technology, which the company has licensed from the Mayo Clinic.
The MRE sequence takes about 15 seconds and can be performed at the end of a standard 45-minute MRI liver exam. If doctors could more easily diagnose liver fibrosis (scarring caused by the hepatitis C virus) or cirrhosis (characterized by the replacement of liver tissue with fibrous scar tissue), they could "treat, halt and in many cases reverse the disease," Ehman says. The technology, he adds, also holds out the possibility of early detection of liver cancer.