Mag-Guard › Technology & Cooling
Background

How does MRI cooling work?

To generate the extremely strong magnetic field, coils are located inside the magnet. For these to be resistance-free — a property called superconducting — the coils must be extremely cold. This is achieved using liquid helium, which has a temperature of −269 °C (4 Kelvin). This temperature inside the magnet is maintained by a cold head and a helium compressor. Together, they produce the characteristic rhythmic sound in the magnet room.

The Cooling Circuit

Structure of the Cooling Circuit

The helium compressor itself requires cooling to operate. It is part of a water cooling circuit that also includes the MRI electronics. This circuit is cooled via a heat exchanger by an external air conditioning unit — typically located on the roof.

The compressor supplies the cold head inside the magnet via a separate circuit with highly compressed helium gas. The cold head keeps the magnet at 4 K (−269 °C), enabling superconductivity in the magnet coils.

If the AC unit fails, the water in the cooling circuit warms up. The MRI electronics and the compressor are then automatically shut down.
The window from AC failure to the shutdown of MRI components is only a matter of minutes.
MRI Cooling Circuit MRI COOLING CIRCUIT Air Conditioning external cooling source Supply Return Heat Exchanger coupling of circuits Supply Return Supply Return MRI Electronics Compressor Helium Pump HELIUM GAS CIRCUIT (SEPARATE CIRCUIT) Magnet Cold Head inside magnet · 4 K high pressure relaxed (return) Supply (Circuit 1) Return (Circuit 1) Supply (Circuit 2) Return (Circuit 2) He gas
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