Open MRI

An open MRI is a scanner built with a much wider, open-sided design instead of the narrow tunnel of a conventional machine. The magnet sits above and below you rather than surrounding you completely, so there is open space on the sides. It exists mainly to make scanning possible for people who cannot manage a standard closed scanner — those who feel strongly claustrophobic, some larger patients, and occasionally children or anxious patients who are reassured by the open space.

The underlying physics is the same as any MRI: a magnetic field and radio waves are used to build detailed images of the spine's soft tissues, with no X-rays involved. The difference is the shape of the magnet. Because an open design cannot generate as concentrated a field, many open scanners run at a lower magnetic field strength than a high-field closed machine. Field strength is one of the things that determines image sharpness, so pictures from a lower-field open scanner can be slightly less detailed, and a scan may take a little longer to gather an equivalent amount of information.

The experience is designed to feel less enclosing. You lie on the table with open space around you, which many people who struggle in a tunnel find far easier to tolerate. As with any MRI, the scan is painless, you will be asked the same careful metal-safety questions beforehand, you will hear knocking and buzzing noises, and staying still remains important for clear images.

An open MRI means that people who would otherwise be unable to complete a scan can still have their spine imaged without radiation. The trade-off is image quality: for fine assessment of the spinal nerves and cord, a standard high-field closed scanner is generally preferred where a person can tolerate it. The choice between the two balances comfort against the level of detail the clinical question requires.

• —Royal College of Radiologists — iRefer: Making the Best Use of Clinical Radiology
• —MHRA — Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use
• —British Association of Spine Surgeons (BASS)

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.