By Michael Profeta

Radio Frequency Shielding is one of the most important factors to consider when planning an MRI suite because it has a direct impact on image quality. The RF shield is built to keep electrical, or RF noise found in our everyday environment from getting onto the images. Like the foundation of a building, everything else depends on the structural soundness and long term reliability of the shield.

The shielding consists of a metal layer installed in the structure of the MRI exam room, including walls, floor, and ceiling. All the seams need to be continuous and tight. Even a short slice will compromise the shield performance. Anything that enters or exits the MRI exam room such as air conditioning, electrical wires, and plumbing lines need to pass through special filters or waveguides.

In the early design stages:
Interview architects and construction companies to be certain they have prior experience in the design and construction of MRI suites. There are many special requirements and guidelines that vary between manufacturers. Having experienced professionals familiar with the brand MRI machine you are considering is a huge plus.

When considering the RF shielding vendor there are several factors to focus on.

Materials, construction styles, and long term reliability should be understood. Get educated on how each vendor builds the shielding. Understand why some materials and methods are better than others. There are reasons for variations in quotes beyond the bottom line. It is important to understand what RF vendors offer in regards to cost, products, quality, warranty, technical support, and on site construction crews. Remember that often times the shielding vendor is more familiar with the MRI requirements than the architect and construction companies. So ask questions and find a shielding vendor that not only has in house expertise, but who also sends expert installation technicians.

After the dust settles
RF shield testing is completed directly after the magnet is installed. Make sure all major construction is completed before the final test. Typical warranties are five years on the shielding and one year on the MRI door and filters. Schedule a follow-up test before the door warranty is up. It may cost you a little extra, but any repairs outside normal wear and tear are covered.

RF shielding needs maintenance
RF shield compromises can cause very subtle to extreme changes in image quality. Elevated levels of background noise or coherent line artifacts can run through the images. Often times the artifacts are intermittent and dismissed as random glitches. A properly maintained MRI shielding system eliminates these artifacts insuring the highest quality image all the times.

There are many reasons why the shielding degrades over time. Accidental punctures, air pressure, temperature variations, condensation, vibration…, the list is endless. Most importantly, the door seal needs scheduled inspections, cleaning, and adjustment.

Implement a planned maintenance program
Planned Maintenance offers increased confidence and assurance of artifact-free MRI imaging. Include periodic door service with yearly RF shield recertification tests. A certificate of compliance should be issued and displayed in the MRI suite area. It does not have to be the original shielding vendor who provides this service. There are companies who specialize in MRI shielding and the maintenance and repairs of all types of MRI shielding. Confirm that field technicians are very experienced properly trained.

What to do if a shielding compromise is detected
When an MRI shield compromise is suspected, a test can be executed to quantify the performance of the shielding. This testing is much different than a compliance test. Finding leaks is an art and a science. Experience is crucial to a successful outcome. Field technicians use state of the art equipment to test your MRI shield. But the test equipment only measures, it has no cognitive skills. Interpreting measurements and finding leaks effectively, is at times a very difficult task. Multiple compromises are not uncommon in old shields adding to the complexity of the problem. Be certain you are paying an individual who has credentials, training, and many years of experience.

About the author: Michael Profeta has an Electronic Engineering Degree and was part of a group of scientists that pioneered the development and installation of the first Whole Body Cryogenic MRI system in North America. He has spent more than 31 years in the MRI field and now owns and operates Magnetic Resonance Technologies, Inc. an Ohio-based corporation that provides turnkey solutions to MRI projects including MRI shielding and testing.