Up-to-date coils add clarity to 3T spine imaging

Difficulties in maintaining field homogeneity over a wide area have traditionally restricted 3T MRI studies to small fields-of-view. Increasing the magnetic field strength means more eddy currents, more distortion, and less field uniformity. These problems can, in theory, be countered by increasing the scanner's bore and diameter.

Back in the real world, however, issues of patient size, comfort, and possible claustrophobia prevent development of long, tubelike magnets.

As with so many other MR applications, the answer to this conundrum appears to lie with better coil technology. Centers using the most up-to-date coils are being rewarded with higher quality images of large anatomic regions they had previously struggled to see clearly at 3T.

"Up until a year or two ago, spine imaging was particularly challenging," said Dr. Meng Law, an associate professor of radiology and neurosurgery at New York University Medical Center. "Because you are scanning over such a large area, it is much harder to obtain the same field homogeneity at 3T as at 1.5T. Generally, artifacts are also exaggerated at 3T, though some of these effects can be countered. For instance, using thinner slices can reduce some of the susceptibility."

As yet, no published evidence exists that 3T spine MRI with advanced coils is any better than imaging at 1.5T. Anecdotally, however, centers are reporting better visualization of disc herniations and annular tears in the spinal canal, Law said. Some radiology departments also claim to see more multiple sclerotic plaques when imaging at 3T.