MR Unsafe (crossed MR in a circle)
The definition FDA’s guidance adapts from ASTM F2503:
“An item which poses unacceptable risks to the patient, medical staff or other persons within the MR environment.”
ASTM F2503 (cited by FDA MR labelling guidance) · ASTM F2503, the practice FDA’s MR labelling guidance follows
What it means for you
The item must not go into the MRI scanner room. Tell the scanning team if you carry or wear a device with this mark.
Whether a device is right for you is a question for your pharmacist, nurse or doctor.
- What it looks like
- The letters MR inside a circle with a diagonal bar across it.
- Where you see it
- Ferromagnetic equipment such as steel oxygen cylinders, and wearable sensors or pumps whose makers say they must come off before a scan.
- Other names
- MRI unsafe; MR Unsafe
What it does not tell you
It does not say what to do instead (remove the device, choose another scan) — that is for the clinical team and the device instructions.
Often confused with
An item with demonstrated safety in the MR environment within defined conditions including conditions for the static magnetic field, the time-varying gradient magnetic fields and the radiofrequency fields.
More symbols in “MR”
Sources
Taken from 3 publishers’ public documents. Each was fetched and read on the date shown:
- US Food and Drug Administration: Testing and Labeling Medical Devices for Safety in the Magnetic Resonance (MR) Environment — guidance issued 10 October 2023 — Defines MR Unsafe as “a medical device which poses unacceptable risks to the patient, medical staff or other persons within the MR environment”; electrically active devices “should be designated either MR Conditional or MR Unsafe, but not MR Safe”. Checked 2026-09-25.
- Boston Scientific: Symbols Glossary — Lists ASTM F2503-20 7.3.3 “MR Unsafe — An item which poses unacceptable risks to the patient, medical staff or other persons within the MR environment.” Checked 2026-09-25.
- NE Scientific: Master Symbol Glossary (CTF-100011 Rev 01) — Shows MR in a circle with a diagonal bar for ASTM F2503 “(MR) Unsafe”. Checked 2026-09-25.
Plain-language parts are in our own words; quotations are the sources’ wording.