3T head coil offers advanced clinical capabilities in MRI

A new breed of MR coil, developed by Minneapolis-based MR Instruments, has entered the 3T marketplace. The TEM (transverse electromagnetic) 3000 coil delivers up to 30% more signal and uses 40% to 60% less energy than the head coils now shipping with 3T scanners, according to Oded Gonen, Ph.D., a professor of radiology, physiology, and neuroscience at New York University School of Medicine.

The improved performance translates into shorter scan times, better images, and improved safety for patients, Gonen said. But its greatest value could be its implications for the future.

Vendors are promoting 3T as the new gold standard for routine clinical scanning. To win acceptance, they proclaim the clinical advantages of 3T as demonstrated at luminary sites. But many of these are research applications achieved using custom-made coils. That's where TEM 3000 comes in.

About a dozen of the new coils have been produced since January, mostly for luminary sites. The work these early adopters are doing represents the leading edge of 3T applications, but the technology they are using is available to any site in the world.

The first batch of coils was built with an interface to Siemens equipment. An interface compatible with GE's 3T systems should be ready by midsummer, and a Philips-compatible version is expected next year.

Gonen has used the TEM 3000 coil to assess patients with multiple sclerosis and head trauma. The goal is to reveal information that can help predict these patients' clinical course. He uses the coil to perform routine 3D spectroscopy of the brain-not just points in the brain or even a slice of it, as is done at many luminary sites, but a large slab of it.

"We excite large volumes in the order of more than a half-liter," he said. "We can look at most of the white matter and a fair amount of the gray matter in the brain."

This mass of tissue can be subdivided into thousands of voxels, each about the size of a small fingernail. Spatial resolution is less than 1 cc, Gonen said.

The NYU approach to spectroscopy is unique in that it precedes imaging studies. Spectroscopy is performed first to search for chemical signs of pathology, which serve as points of interest to be examined visually. This is the only practical way to perform MRS, he said.

"If you already know where the damage is based on MRI, doing spectroscopy doesn't provide much added value," Gonen said.

The prospect that a production-line head coil might open new opportunities in spectroscopy may be of less interest to the general imaging community, which is focused on imaging. But TEM 3000 offers advantages for routine imaging as well, according to Gonen. When used for MRI, the coil delivers improved sensitivity that can be traded for shorter examination protocols. It requires less power and is therefore safer because it deposits less energy in the patient, and it generates better signal to noise. It is also "patient friendly."

"TEM 3000 is not only a more effective antenna, which is what a good coil is, but it is packaged so it won't scare people away," he said.

Research coils often are more functional than esthetic and can be intimidating to the uninitiated. TEM 3000 has the same "refined" look as production-line coils and is more spacious than many competing models. Its size reduces patient discomfort and offers greater flexibility in use. The coil can accommodate the bandages of postsurgical patients, for example, and ancillary equipment such as headphones and oxygen masks needed for functional MRI.

TEM 3000 is the first of what MR Instruments expects to be a long line of high-performance 3T coils. With relatively minor modifications, it can be turned into a knee or an elbow coil. Engineers at the company are also working on a multinuclei coil that will allow spectroscopy not only of hydrogen metabolites, as is now possible with TEM 3000, but of other elements, such as fluorine, phosphorus, or oxygen. A production-line version of the multinuclei coil is scheduled for release later this year.