Honey, I shrunk the magnet: 7T MRI runs cryogen-free

2014 07 28 13 27 00 438 Mr Solutions 7 T Scanner 400 20140728202723

Looking to fill a void in the market for preclinical MRI and eliminate the need for labs to hunt down scarce supplies of liquid helium, MR Solutions has developed a new cryogen-free, compact 7-tesla scanner for research applications. The system generated great interest at the global MRI congress held in Milan, Italy, during May.

The company is touting the device's ability to provide enhanced soft-tissue contrast and molecular imaging capability, all while taking up roughly the same space as a large desk. The scanner also features an elliptical field-of-view that is more suitable for research purposes.

In addition, the scanner is designed to significantly reduce the adverse residual effect that its powerful 7-tesla magnet would have on nearby equipment, such as PET and SPECT devices.

The advantages of 7-tesla MRI include greater sensitivity and spatial resolution and faster scans, with particular utility for functional MRI (fMRI).

MR Solutions CEO Dr. David Taylor.MR Solutions CEO Dr. David Taylor.

"Basically, it is anatomical imaging that you can do comfortably at 3 tesla, but the functional MRI gets easier and easier as you go up in field strength, as does the spatial resolution," said physicist and MR Solutions CEO Dr. David Taylor.

In its current configuration, the 7-tesla preclinical scanner is designed primarily for imaging rats and mice, with a bore size of 17 cm. "The next magnet coming down the pike will be a larger bore that will allow us to image rabbits and monkeys at 7 tesla with a bore of 24 cm," Taylor said.

The genesis of the 7-tesla MRI project began last year, soon after Agilent Technologies exited the preclinical MRI market. Its departure left MRI developer Bruker as the primary company in the preclinical MRI arena and gave MR Solutions a potential opening.

"We saw this as a serious opportunity to develop a higher field, cryogen-free magnet rather than a conventional 3-tesla magnet in order to differentiate ourselves," Taylor said.

MR Solutions set a goal to develop a high-field compact preclinical MRI unit that, among other features, "would sit in an ordinary laboratory next to other preclinical modalities like PET and SPECT without a negative effect," Taylor said. "Most MRI systems are fairly hostile to other technologies because of the large magnetic field."

To eliminate the impact of the powerful 7-tesla magnet, MR Solutions installed a solenoid coil, which creates a uniform magnetic field around the device to control and reduce any stray magnetism to within a few centimeters.

Cryogen-free technology

The cryogen-free feature is made possible by the company's use of a superconducting wire, or cryocooler, which lowers the temperature of the 7-tesla magnet coils to 4 K (-269° C or -452° F). The cryocooler thus eliminates the need for liquid helium or liquid nitrogen.

"The real technical challenge is for that cryocooler to be able to cool those coils down to 4 K, hold them there, and fight any heat leaks into the magnet from the lab," Taylor said. "That requires a lot of innovation in the way the magnet is designed, the way it is fabricated, the use of materials, and so on."

The technology is also designed to help laboratories circumvent the helium shortage that has stymied hospitals, imaging centers, and research facilities around the world. Conventional preclinical MRI scanners generally require a few hundred liters of helium to operate.

MR Solutions' 7-tesla preclinical MRI scanner is about the size of a large desk.MR Solutions' 7-tesla preclinical MRI scanner is about the size of a large desk.

The shortage has forced some labs to shut down temporarily, because they were unable to buy the commodity.

"This is a worldwide problem," Taylor said. "The magnet has a quench, and if it loses the helium, you need several hundred liters of helium to cool it down again. You may have to wait six months" to get a supply.

Needless to say, Taylor predicted that the future of MRI is in "cryogen-free magnets, and even clinical magnets will eventually go cryogen-free."

Because conventional preclinical MRI scanners require liquid helium to cool coils, the devices themselves are large and can weigh approximately 3,000 lb (1,350 kg). With no need for a helium supply and related hardware, MR Solutions' cryogen-free 7-tesla system weighs less than 1,100 lb (500 kg).

The cryogen-free technology also eliminates the need for a facility to make infrastructure changes to accommodate pipes for the helium and ways to vent the gas, according to Taylor.

The future of 7T

Taylor believes the development of this 7-tesla technology opens the possibility of increasing magnet field strength to even greater levels for preclinical MRI scanners. "The electronics are already here waiting, so it depends purely on magnet development," he added.

As preclinical magnet strength increases, he also sees the potential for MRI's use in drug trials, if regulatory approval can be achieved.

"I imagine that would dramatically improve the efficiency of [drug] development in the preclinical world, but it would be a big regulatory effort," he added. "At the moment, we're into sequential sacrifice and histology. I think MRI could replace those [tests], but it has to go through this proving process for more inexpensive, compact MRI systems."

So far, MR Solutions has installed three systems in the U.S., Mexico, and France. The company, based in Surrey, U.K., has a subsidiary in Boston and another subsidiary in Australia.

The system was on display recently at the joint meeting of the International Society for Magnetic Resonance in Medicine (ISMRM) and European Society for Magnetic Resonance in Medicine and Biology (ESMRMB) in Milan and at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) annual meeting in St. Louis.

Page 1 of 549
Next Page