Vendors showcase coil quality control at ISMRM meeting

Identifying individual coil elements and channel failures is getting more difficult as the number of channels in commercial MR scanners increases, according to Ceylan C. Guclu, a development engineer at GE Healthcare. The repeatability of quality checks is also a problem. For sites struggling with these difficulties, GE has a solution.

In a presentation May 10 at the International Society for Magnetic Resonance in Medicine, Guclu reported on the development at GE of an automated software tool for identifying element failure in multielement coils. The technique was developed to be "immune" to external field disturbances, he said, thereby making the results more repeatable.

The test is relatively simple. Using a multichannel head coil, for example, images are acquired at 256 x 64 pixels from each channel, while a spin-echo sequence is applied. The radiofrequency is then turned off to allow the coil to acquire only noise. The software integrates the signal and noise from each channel and subtracts the noise. Results are then analyzed according to pass/fail criteria.

"You can automatically test the coils one by one," Guclu said. "This tool gives a noise correlation matrix for further troubleshooting and analysis."

The technique, which is designed for use at installed sites, has proven to be "quite robust" in routine assessments of coil performance, he said.

The need to ensure quality coil operation has also spawned independent solutions. One, a family of coil analyzers called Bravo MRI, is available from AEA Technology. Another, Via Echo, will be available from the company in late summer.

Both feature handheld designs, shown on the ISMRM exhibit floor, that deliver data during coil testing in the magnet that can be compared against technical specifications accompanying the coils. The analyzers hook into connectors on the backs of MR scanners. Operators select the frequency they want to test, and the palm-sized devices do the rest.

"It will work for all kinds of coils," said George Naber, president and CEO of AEA Technology.

Data can be displayed on the handheld product or downloaded to a PC for archiving or display on a larger screen.

The three members of the Bravo family cost between $2000 and $2500, span a frequency range up to 200 MHz, and work in field strengths up to 3T. The Via Echo, which will cost about $3000, will handle up to a gigahertz and work in field strengths including 11.7T, Naber said.

Further distinguishing the Via Echo is a nonmagnetic design that allows the unit to operate in close proximity to the magnet. The Bravo must remain a meter or more away.