RF Shielding

Posted by Rachel Masey

Fri, Apr 4, 2014 @ 10:51 AM

RF (Radio Frequency) Shield_Noise Shielding plays a huge role in the MRI’s ability to provide quality images. It is a requirement for all MRI systems to be housed within a RF Shielded MRI scanning room. The RF Shield is used to keep RF noise from getting into the images.  Radio stations, electrical equipment and other radio frequency signals can all be responsible for potential image damage if they are not protected by the MRI exam rooms’ RF shielding. This particular shielding consists of layers of metal installed in the MRI exam rooms, covering all of the walls, ceilings and floors. The shielding must cover every window, door, even electrical circuits and other gaps that penetrate the room. One open seam, one small puncture or even a slight slice in a shield can cause image damage and poor shield performance. The metals most used to build these protective rooms are are copper, aluminum and galvanized steel. When it comes to price, most facilities will turn to galvanized steel before copper, since copper is well known for being more expensive.

Things to do BEFORE having a RF Shielding room built:

A step that is very important, but usually overlooked is to schedule an evaluation to discern whether or not your site has an electromagnetic interference (EMI) and vibration problem. EMI does not allow your MRI scanner to be utilized fully or properly. These sorts of issues can be generated by power lines, subway trains, nearby elevators and electrical systems, among other things. A solution to EMI issues is to include thick galvanized steel, in addition to your copper and aluminum shielding elements. A Vibration test is also necessary because even though magnets have been recently made lighter and faster, they also are more susceptible to vibrations, which too, can cause image irregularity. Having an evaluation allows you to know whether your MRI room needs a vibration pad or not, which could save you the hassle of having to do late modifications of your scanning room later.

Also before you have your Shield installed, check with your MRIs’ system manufacturer in order to confirm its’ specific requirements. Different Tesla’s require different shielding sense frequencies. For instance, a 1.0T system requires 42.6 MHz, while a 3.0T system requires 63.9 MHz.

Things to be aware of AFTER the RF Shield room is built:

Once the construction of the metal box is complete there are RF filters and waveguides that are also attached inside the MRI room so that everything that comes in will pass through these filters. The RF filters hold data cables but also generate a penetration point for powered outlets and electrical power for lighting. Waveguides are also a penetration within the RF shield. Waveguides allow fluid flow into the room. Examples of fluid flow are air conditioning, medical gases and water.

Safety should always be a concern. To ensure that no one accidently brings in magnetic materials into the MRI scan room, you should have adequate, readable and well distributed, easily seen signs indicating that they are entering into a potentially dangerous area. It’s always a good idea to make visitors and even hospital personnel well aware of their surroundings and environment.

Make sure you always receive a warranty with your purchased RF Shielding room. Warranties usually include 5 years for the shielding but only one year on the MRI door and filters. Make sure to always schedule a ‘follow-up” test way before the door and filter warranty is up. This way necessary cleaning and adjustments can be made. Just like a car needs regularly scheduled oil changes, the RF shielding also needs to have scheduled maintenance checks. Paying for a few repairs early could end up saving you a ton, especially if your warranty ends and you find that issues suddenly arise!