ACR Manual on MR Safety

Published by the ACR Committee on MR Safety, this is the successor to the ACR Guidance Documents on MR Safe Practices (a 2002 white paper, updated in JMRI in 2007, 2013, and 2019). The 2024 edition was considerably expanded — to 146 pages across 16 chapters and 5 appendices — and was formally published in Radiology (Pedrosa et al., 2025). The March 2026 revision added a patient pre-appointment guide, refined the Zone III and IV definitions, updated terminology to peripheral nerve stimulation, rewrote the SAR section, and tightened guidance on unconnected coils and hearing protection.

• Four safety zones (I–IV). Zone III is the MR controlled access area, covering the console and any region where the fringe field extends beyond the scanner room; Zone IV is the scanner room itself. Access is supervised by Level 2 MR personnel.
• A defined personnel hierarchy: an MR Medical Director (MRMD), supported by an MR Safety Officer (MRSO) and MR Safety Expert (MRSE), with staff stratified as Level 1 and Level 2 MR personnel and a standing MR Safety Committee to review incidents and near-misses.
• The supervising radiologist makes the risk–benefit decision and may delegate a function but not the underlying responsibility.

• Screening of patients and staff, ferromagnetic detection, pocketless attire, and the exclusion or tethering of MR-unsafe equipment from Zone IV.
• A “full stop and final check” — a pre-scan time-out with routine and augmented checklists.
• Implant and device management under the ASTM MR Safe / MR Conditional / MR Unsafe framework, with an appendix for unclear conditions.
• Emergency response covering the emergency stop, power-off, and quench controls, mock-code drills, and removal of the patient from Zone IV before a resuscitation.
• Policies for remote scanning (a Level 2 technologist onsite is recommended) and for special populations, including pregnancy, sedation and claustrophobia, and large body habitus.

MHRA — Safety Guidelines for MRI Equipment

Issued by the UK’s medical device regulator, the current version is 4.3 (February 2021). It is non-statutory good-practice guidance but carries regulatory weight, sitting alongside UK device regulation and the Control of Electromagnetic Fields at Work Regulations 2016. It covers procurement, installation, and clinical use.

• Static magnetic field — projectile risk, biological effects, and implant and peripheral-equipment compatibility.
• Gradient fields — dB/dt, peripheral nerve stimulation, and acoustic noise.
• Radiofrequency fields — tissue heating, burns, and SAR.
• Cryogens and quench — asphyxiation risk and quench-pipe integrity.

• Named roles: an MR Responsible Person, an MR Safety Expert, MR Authorised Persons, and Operators.
• A controlled access area defined by the 0.5 mT (5-gauss) contour, with restricted entry and signage at all entrances.
• The referrer is responsible for identifying implants and contraindications before referral, supported by local screening.
• Adverse incidents are reportable to the MHRA.

IEC 60601-2-33

The IEC particular standard for the basic safety and essential performance of MR equipment for medical diagnosis. It is a design standard — it governs how scanners are built, labelled, and constrained — and is the source of the exposure limits that clinical guidance references. National adoptions include EN IEC 60601-2-33.

• Normal — routine operation, with no setting expected to cause physiological stress.
• First-Level Controlled — may cause physiological stress; requires deliberate operator action and medical supervision.
• Second-Level Controlled — significant risk; requires ethics-committee approval for research use.

• Whole-body SAR (6-minute average): 2 W/kg in Normal mode, rising to 4 W/kg in First-Level; head SAR is limited to 3.2 W/kg, with higher limits for local and extremity exposure.
• Static field: up to 3 T in Normal mode; above 3 T and up to 8 T in First-Level; above 8 T is Second-Level.
• Gradient output (dB/dt): limited to roughly 80% of the peripheral-nerve-stimulation threshold in Normal mode, and 100% in First-Level.
• Core temperature rise: no more than 0.5 °C in Normal mode and 1 °C in First-Level.
• Acoustic noise: hearing protection is required, and scanners must warn where noise may exceed about 99 dB(A).

ISMRM / ISMRT Consensus Statements

Produced by the ISMRM Safety Committee with the ISMRT and published mainly in the Journal of Magnetic Resonance Imaging. Rather than a single manual, these are focused recommendations that complement the ACR and MHRA documents:

• Cardiac implantable electronic devices: practical protocols for imaging patients with pacemakers and defibrillators, both MR Conditional and, in selected non-conditional cases, at 1.5 T (Vigen et al., 2021).
• 7 T safety: best-practice recommendations for ultra-high-field clinical imaging.
• MR safety management: recommended responsibilities and governance roles.
• Radiographer and technologist practice issues in MR safety.
• Gadolinium deposition in the brain: a summary of the evidence and recommendations.
• Scanning during a pandemic: operational guidance from the COVID-19 period.