¿Es 7-Tesla MRI donde estaba hace 10 años 3-Tesla?

por Brendon Nafziger, DOTmed News Associate Editor | January 12, 2012

Although it has not been clinically proven to be superior, 7T MRI offers a theoretical benefit over weaker magnets: an increased signal-to-noise ratio. This could lead to higher resolution or faster scans.

"You could get a better delineation of, for example, brain structures," White said. "So that allows you to visualize disease that's not as easily visualized, possibly cannot be visualized at 3T, and potentially allows earlier diagnosis and treatment."

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Neurology is, actually, one of the leading fields for the high-powered magnetic technology, especially functional magnetic resonance imaging. In 2010, researchers published an atlas of the brain using 7T MRI scans. And just last year, researchers used a 7T device to better detect the brain scarring that can trigger epilepsy.

Other promising applications include orthopedics and magnetic resonance angiography, especially non-contrast-based MRA.

New coils needed

But to take advantage of 7T MRIs, scientists need to first develop coils -- which help capture the patient images -- that can work with their much higher field strength.

This has been challenging, in part because when making coils for the new system, it's harder to achieve what's known as B1 homogeneity.

"B1 is the time varying magnetic field generated by the RF coil which is used to generate the image. Better B1 homogeneity contributes to better image quality," White explained.

At higher field strengths, such as in 7T MRIs, dielectric effects influence the homogeneity of the B1 field, White added. This can result in shading and other contrast effects. But scientists can mitigate this effect by using multiple transmit channels at the same time, with independent control of phase and amplitude to perform what's known as "B1 shimming."

Capturing the heart

Philips said it continues to develop new coils -- both in-house and with third parties. And progress is being made on the coil front, including for heart imaging.

For instance, Siemens and its academic collaborators said they've developed a multi-channel RF coil able to acquire heart images.

According to a study published last March in the Journal of Magnetic Resonance Imaging, researchers with the Berlin Ultrahigh Field Facility developed four-channel cardiac transceiver coils for the 7T MRI. The project was the result of a joint collaboration with scientists from Siemens and Charité-Universitätsmedizin Berlin, one of Germany's biggest university hospitals, and Max-Delbrück-Center for Molecular Medicine Berlin-Buch, a German research center.

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