MRI pioneer struggles against conventional thought

New gradients could make scans safer

MRI pioneer Sir Peter Mansfield is developing a new generation of gradient coils that promise to allow faster, safer, quieter scans in very high field scanners. The coils are being built by General Magnetic, the private Nottingham, U.K., R&D company founded by Mansfield. The company has developed techniques that remove what Mansfield believes are the two main obstacles impeding ultrafast imaging--acoustic noise and induced currents in patients.

Mansfield claims his techniques reduce acoustic noise by up to 50 dB and significantly reduce induced currents. Despite such advantages, however, his company has had no success selling or licensing the related patents.

"Major companies have their own well-paid in-house research groups. I am guessing they feel they shouldn't have to buy ideas when they have their own ideas people," he said. "But the reality is we are able to reduce noise by an astronomical amount that others cannot get near."

Industry may not be listening, but the MR community is, at least in Europe. In a paper presented at the European Society for Magnetic Resonance in Medicine and Biology in August, Mansfield noted that problems with acoustic noise relate to the static field strength and the modulation frequency. For fast imaging in magnetic fields of 3T and more, noise levels can exceed 130 dB, which is well beyond permitted safety levels.

Mansfield's echo planar imaging (EPI) technique transformed MRI. Gradient coils typically generate induced currents, which produce tingling sensations and involuntary muscle twitch in patients. Neural stimulation could trigger epileptic seizures and/or cardiac fibrillation.

The induced currents in MR subjects are a result of the E-fields produced by the gradient coils. It is important to be able to measure and monitor these fields in order to document the effectiveness of the coils being developed by General Magnetic. To that end, the company has built specialized differential E-field probes and associated screened electronic circuits. Once the coils are proven clinically, Mansfield believes manufacturers will follow his lead.

"You can have a brilliant idea, but people are cautious until they see that it works, which is not unreasonable," he said. "We have a gap to bridge in terms of credibility, but I would put money on the bet that once it is shown in practice, it should be a winner."

General Magnetic was founded in 1994 as a vehicle for selling and licensing intellectual property, but Mansfield has since broadened his company's mission. Last year, the firm, which is funded entirely by Mansfield, began developing coils, with the aim of showcasing them in high-profile medical centers.

One coil, which offers acoustic noise reduction, is in development and could be ready by March 2003. A second coil, designed to dampen induced currents, should be developed in about 12 months, he said. General Magnetic plans ultimately to create one coil that will offer advantages in both areas.

Mansfield will custom-design coils for imaging facilities for demonstration purposes. The opportunity for such custom designing is limited, however, because most MR systems are compatible only with gradient coils made by the scanner's OEM.

"There are a few high-profile units out in the field that enable people to buy a coil and add it themselves," he said. "We will target them initially."

Mansfield emphasized, however, that his company is still focused on R&D and not manufacturing. Coil production, he said, is only a means to an end. He expects that once the new coils are in use, their design will catch the industry's attention. If not, he is hopeful that regulatory authorities will be persuaded to mandate their use. His confidence is rooted in his past experience as the developer of EPI.

"One of the big payoffs--not financially, but in terms of personal satisfaction--is that high-speed imaging has come of age," Mansfield said. "Now everyone wants to image faster and faster. I was saying this 20 years ago, and people pooh-poohed it and said it wasn't possible. Now everyone wants to do it in milliseconds.

High-speed imaging continues to spur major developments in applications addressing areas of the body susceptible to motion artifact, such as the heart and abdomen, and the brain, where ever faster imaging has allowed the study of normal and abnormal processes.

"This is a fantastic time to be in the imaging business," he said.