Why Are EEG Rooms Shielded? Interference-Free Measurement in Hospitals
Brain waves are very weak signals. How hospital interference affects EEG measurements and what a shielded room brings.
3 min readSeptember 9, 2026
Why Is an MRI Scanner Shielded?
An MRI scanner forms images by receiving very weak radio-frequency signals from the body. These signals are so weak that noise from a nearby radio transmitter, a lift or another medical device shows up in the image as lines and artifacts.
The RF cage isolates the MRI room from outside radio signals so the scanner receives only the signal from the patient. Without a cage, scanner manufacturers usually won't accept the installation.
RF Cage vs Magnetic Shielding
The RF cage stops radio-frequency signals; it is usually built from copper or galvanized steel panels. Limiting the strong static magnetic field of the MRI magnet from extending outside the room is a separate matter and may require magnetic shielding made of steel.
Which measure is needed depends on the scanner's field strength and how the areas around the room are used. This is calculated together with the manufacturer's site plan.
Doors, Windows and Penetrations
MRI rooms use a shielded window so the technician can see the patient. A fine metal mesh between two panes blocks signals without obstructing the view. The door, opened and closed often, is the most carefully designed part.
Special waveguide penetrations are used for gases, oxygen, contrast media and cables. Every penetration into the room is checked individually during the shielding measurement.
Acceptance and Periodic Measurement
Before installation, the scanner manufacturer requires a test report showing the cage achieves a set attenuation. The measurement is usually made around the scanner's operating frequency.
Door gaskets can wear over time; if unexplained artifacts start appearing in images, the door is the first place to check. Annual maintenance and measurement catches these problems early.
Frequently Asked Questions
Are MRI rooms and EEG rooms shielded the same way?
No. An MRI room is shielded against high-frequency RF signals, while an EEG room is mainly shielded against low-frequency mains noise; materials and details differ.
Can the cage of an existing MRI room be renewed?
Yes. When the scanner is replaced, the cage is measured; if needed, the door, gaskets and penetrations are renewed to meet the new scanner's requirements.
How long does a cage measurement take?
Depending on room size, it is usually completed within one working day.
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