Distinguish the September correction from the July rewrite
MHRA describes its September 30, 2026 update as diagram changes and other corrections. The fifth-edition rewrite was introduced on July 30, followed by an August 13 update to the cover, UKAS information and other minor details. September should not be presented as establishment of an entirely new MRI safety regime.
The current guidance addresses procurement, installation, clinical use and maintenance. MRI manufacturers, accessory suppliers and application teams can use it to understand the information needed at the point of use. Its technical explanations are not all newly imposed legal obligations in September.
RF heating, implant conditionality and quench venting concern scan parameters, device evidence and installation systems respectively. Combining them into a uniform new high-field room rule obscures those distinctions.
A 1.5 T or 3 T label does not establish 7 T suitability
Section 4.5.4 explains additional considerations at 7 T and above. Higher RF frequencies shorten wavelengths in tissue and can increase field inhomogeneity and localized heating. Local hotspots can remain limiting even where global SAR is within accepted thresholds.
Global SAR and local heating therefore answer different questions. A satisfactory global indicator alone does not establish control of every local thermal risk. Nor does higher field strength alone establish that a particular implant is necessarily more dangerous; the guidance calls for attention to factors including device geometry.
MR Conditional information must be read with its conditions. Evidence for 1.5 T or 3 T does not automatically support 7 T use. The guidance notes that many such devices are not approved, or have not been assessed, for 7 T. Whether evidence covers the proposed field strength, device model and scanning conditions is a specific question about the claim.
The guidance distinguishes MR Safe, MR Conditional and MR Unsafe and uses MR Unlabelled for items without those labels. Lack of a label does not establish safety. For accessories, positioning devices or emergency supplies, a generic statement of MRI compatibility does not replace the classification and associated conditions.
Those conditions are information manufacturers need to communicate accurately. They identify the circumstances supported by safety evidence rather than merely adding an MRI symbol to a product.
Hearing protection and quench venting need different information
Alternating currents cause gradient coils to vibrate in the magnetic field, producing acoustic noise. The guidance addresses manufacturer characterization of expected maximum noise and distinguishes measures such as maximum gradient acoustic noise and maximum clinical acoustic noise. Protection needs the equipment information and relevant scanning conditions.
SNR and NRR protection ratings are not interchangeable. Entertainment headphones without an appropriate protection rating or conformity marking should not be assumed to protect hearing. Receiving audio through headphones is distinct from having adequate hearing protection.
Accessory protection capability needs the relevant labeling, and scanner instructions need to support selection of appropriate protection. A statement simply to wear headphones may omit the information required to make that selection.
Quench venting concerns the magnet and installation. Cryogenic-gas release from superconducting systems can create risks including oxygen deficiency. The fifth edition includes basic quench-pipe installation and specification guidance; the assessment extends beyond a control button to the actual discharge arrangement.
Manufacturer requirements and installation conditions need to be considered, with distinctions between magnet types and cryogen arrangements. The guidance does not support a claim that one particular venting interlock became uniformly mandatory in September.
Field-strength claims, acoustic parameters, protection labels and installation instructions support different safety decisions at the point of use. A generic high-field safety statement does not convey those conditions.
Sources
- Primary official sourceMagnetic resonance imaging equipment in clinical use: safety guidelines (opens in a new tab)Medicines and Healthcare products Regulatory Agency
- Supporting sourceSafety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use — fifth edition (opens in a new tab)Medicines and Healthcare products Regulatory Agency