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All Together Now
Magnetic Resonance Elastography (MRE)
The premise: "The trick here is that things that are really stiff, when you move them, they all move together," says JohnWeaver, the MRE project leader. A well-known property of cancerous tissue is that it is stiff—as any woman who has found a lump in her breast knows.
Imaging researchers will often invent a way to capture a picture of a certain property, explainsWeaver, and then try to figure out whether it offers any useful information.With MRE,Weaver began with something known—the fact that cancer is stiff—and is working backwards to capture an image of it.
In MRE, very-low-frequency waves pass through the breast and vibrate the tissue. An MRI scanner with specialized software measures that motion and estimates what distribution of stiffness within the breast would cause those measurements. Until a couple of years ago, DHMC did not have an MRI scanner designated exclusively for research. So in order for women to participate in the MRE study, they often had to come in for the investigational exam late at night, when the clinical MRI machines were not in use. This scheduling hurdle made it difficult to develop the technology as quickly as the other modalities. Now, however, DHMC has an Advanced Imaging Center, so Weaver is making much faster progress.
The Dartmouth team is not the only group in the world looking at MRE for breast imaging, but its findings are among the most developed, according to Weaver. He anticipates MRE being used to better diagnose abnormal tissue and to avoid unnecessary biopsies, as well as to monitor the success of chemotherapy treatments.
The procedure: From the patient's perspective, an MRE exam is very similar to a standard MRI. The main difference is that the woman lies face down, with her upper torso on a sliding apparatus that looks like a rolling cart or tray. The tray has two holes for her breasts, and the breast being examined rests on a vibrating plate. The low-frequency
The MRE apparatus (pictured in the lower left photo) consists of coils—which surround the breasts and interact with the MRI machine (pictured on the bottom right)—plus a plate (pictured in a close-up view above) that uses piezoelectric crystals to create controlled vibrations in the breast tissue.
vibrations can be felt by the patient but are not uncomfortable.
Inside the device are coils that sense the vibrations in the tissue and interact with the MRI magnet to actually create the images.
Jennifer Durgin is Dartmouth Medicine's senior writer.
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