High Yield MRI

MRI Screening, Patient Prep & Positioning

MRI Screening, Patient Prep & Positioning: A Practical Guide

For radiographers / technologists, nurses and students. Practical workflow from door to bore — screening, triage, coil setup, comfort, and Zone IV emergencies.

⚠ The magnet is ALWAYS ON. The static field does not switch off between patients, overnight, or during a power cut. Ferromagnetic objects (O₂ cylinders, poles, scissors, wheelchairs, crash carts, hair pins) become lethal projectiles the moment they cross the 5 gauss line. Every person and object entering Zone IV must be screened, every time.
Educational use only. This is a teaching aid. Local departmental policy, the manufacturer’s Instructions for Use (IFU), the MR-conditional labelling for each device, and your MR Safety Officer / MR Medical Director / MRSE guidance always govern actual practice.

1 · The Four Safety Zones ACR-defined access control I → IV

Zone I

Zone I — Free public access

What it isAll areas freely accessible to the general public — outside the MR environment (car park, general corridors, waiting areas).
Who / whatAnyone. No screening required. No field hazard here.
Zone II

Zone II — The interface

What it isThe buffer between public Zone I and controlled Zone III. Patients are greeted, screened, changed and gowned here, under general supervision of MR personnel.
Who / whatPatients (supervised); screening happens here — the last chance to catch hazards before the controlled area.
Zone III

Zone III — Restricted / controlled

What it isArea where free access by unscreened people or ferromagnetic objects can cause serious injury — control room, computer room. Physically restricted by locked doors / access control, supervised by Level 2 MR personnel.
Who / whatOnly screened patients and MR personnel. Non-MR personnel must be screened AND escorted at all times.
Zone IV

Zone IV — The magnet room

What it isThe scanner room itself — definite, potentially lethal projectile risk. Marked with warning signage / lights.
Who / whatOnly screened patients under direct Level 2 MR-personnel supervision. Nothing ferromagnetic enters — ever. The room is never left with an unmonitored patient or open access.
MR personnel levels & escort rules (who’s allowed to supervise)
  • Level 1 MR personnel — passed minimal safety education for their own safety in the MR environment.
  • Level 2 MR personnel — more extensively trained (RF heating, projectiles, quench). Only Level 2 personnel supervise Zone III/IV.
  • Non-MR personnel — anyone not recently/frequently working in the MR environment. Must be screened and continuously escorted, never left alone in Zone III/IV.
  • Accompanying persons (parents, carers, interpreters) are non-MR personnel — same screening as the patient before entering Zone IV.

2 · Patient Screening & Its Pitfalls the form is a start, not the answer

Golden rule: the screening form is a prompt for a conversation, not a substitute for one. Verbally verify high-risk answers — patients under-report, mis-remember and misunderstand. When a device is declared, confirm exact model & MR conditions against the manufacturer IFU. Use the site’s Implant Safety Checker to look up device-specific conditionality.
Under-reporting

“I don’t have anything metal”

PitfallPatients forget old implants, don’t consider stents/clips/coils “metal”, or omit dental/orthopaedic hardware.
DoAsk open questions: “Have you ever had ANY operation, anywhere on your body?” Probe visible scars. Cross-check old records/prior imaging. When in doubt, don’t scan — escalate.
Unknown implant

“I had surgery but don’t know what”

PitfallThe classic unknown implant — scanning could subject an unlabelled/legacy device to unsafe fields, RF heating or torque.
DoObtain the operative note / implant card / registry entry, or radiograph to identify hardware. Escalate to the MR Safety Officer / radiologist for a documented decision.
Language / comprehension

Language barriers & capacity

PitfallA patient who nods “yes” to everything, a form completed by a relative, or health-literacy gaps make the form meaningless.
DoUse a professional interpreter (not family) and translated forms. Confirm by teach-back. Document who screened and how.
Unconscious / paediatric

Unable to self-report

PitfallUnconscious, sedated, intubated, confused or very young patients cannot answer.
DoScreen via notes, next of kin, GP records and radiographs. Treat as unscreened until proven otherwise. Account for every line, pump, lead and ferromagnetic ITU item before entry.
Cosmetic

Tattoos, permanent make-up & patches

PitfallSome tattoo/PMU inks contain iron-oxide pigment → heating. Transdermal patches (nicotine, GTN, fentanyl, HRT) may have a metallic backing → RF burn AND altered drug delivery.
DoAsk about all patches — remove and replace after the scan per policy. Advise on cosmetic risk; monitor tattooed areas; ask the patient to report heating immediately via the call bell.
The people, not just the patient

Screen staff & accompanying persons

PitfallCarers, interpreters, porters, cleaners, other clinicians and students carry their own hazards (pacemakers, aneurysm clips, pockets of pens, keys, phones, O₂ cylinders).
DoEveryone crossing into Zone IV is screened to the same standard and empties pockets / removes ferromagnetics. No exceptions for staff.
Pre-entry screening checklist (verify verbally, then again at the door)
  • Identity confirmed & correct patient / correct examination
  • “Any operation ever, anywhere?” — implants, clips, coils, stents, valves, hardware
  • Cardiac device / pacemaker / ICD / loop recorder / leads (present or removed)
  • Cochlear implant, neurostimulator, programmable shunt, infusion/insulin pump
  • Aneurysm clip; metallic foreign body; shrapnel/bullet; occupational metal exposure
  • Orbital FB risk — metalworker / grinding / welding history (→ orbital radiograph if any doubt)
  • Pregnancy status / possibility (esp. first trimester); breastfeeding for contrast counselling
  • Renal function / eGFR if gadolinium contrast planned
  • Tattoos / permanent make-up noted; transdermal patches identified & removed
  • All external metal removed: jewellery, piercings, watch, phone, keys, coins, hair clips, hearing aids, dentures, glasses, underwired bra, metal-containing clothing
  • Accompanying person / escorting staff separately screened
  • Device conditionality confirmed against IFU (field strength, SAR/B1+RMS, gradient, positioning, wait-time)

3 · Contraindication Triage stop · verify · proceed under conditions

Stop
Cardiac implantable devices (legacy pacemaker / ICD) — older non-conditional devices are a relative-to-absolute contraindication (lead heating, inhibition, reprogramming, arrhythmia). MR-conditional systems may be scanned ONLY with cardiology involvement, device in MR-mode, and every labelled condition met. Confirm both generator AND leads are conditional.
Stop
Cochlear & active auditory implants — many are conditional only after magnet handling / at specific field strength; some have an internal magnet needing removal; risk of demagnetisation, torque, pain, artefact. Verify the exact model IFU.
Stop
Aneurysm clips — a ferromagnetic intracranial clip can torque and cause catastrophic haemorrhage. Requires documentary proof the specific clip is non-ferromagnetic / MR-conditional. Unknown clip = do not scan.
Verify
Neurostimulators (DBS, SCS, VNS, sacral) — conditional under strict, often complex limits (transmit coil, SAR/B1+RMS caps, device off/settings). Involve the managing team.
Stop
Metallic foreign body — the orbit. The classic scenario: a metalworker / grinder / welder with possible intra-ocular fragment. A ferromagnetic orbital FB can move and blind the patient. Orbital radiograph (or CT) to exclude before scanning if any occupational history or symptoms.
Verify
First-trimester pregnancy — MRI is not known to harm the fetus, but scan only when the benefit justifies it and the question can’t wait. Avoid gadolinium unless essential. Follow local policy and radiologist authorisation.
Often OK, conditionally
Most modern orthopaedic hardware, coronary/peripheral stents, heart valves, sternal wires, joint replacements — usually MR-safe/conditional, but still confirm the model and any post-implant wait-period. Expect artefact; plan metal-artefact-reduction sequences.
Escalation: any “Stop” or unresolved “Verify” is a documented decision for the radiologist / MR Safety Officer / MR Medical Director — not a decision made alone at the console.

4 · Coil Selection & Positioning Basics SNR, comfort & RF-burn prevention

Coil

Choose the right coil

  • Match the coil to the anatomy; the smallest coil that covers the ROI → best SNR.
  • Coil element over the target, plugged into the correct port, elements enabled.
  • RF heating is driven by the transmit coil — mind the transmit field when an implant sits within it.
Isocentre

Centre the anatomy at isocentre

  • Place the ROI at isocentre using the laser landmark — best B0 homogeneity, gradient linearity and fat-sat.
  • Off-isocentre → distortion, failed spectral fat suppression, lower signal.
  • Straighten and support the part; avoid rotation off-centre.
RF burns

Prevent skin-to-skin & cable loops

  • No crossed limbs — uncross ankles, keep hands off flanks/thighs. Skin-to-skin contact forms a conductive loop → burn.
  • Pad between calves, between hands and body, and any bare-skin contact.
  • Route coil cables straight — no loops; keep cables off the skin.
  • Pad the patient off the bore wall — no bare skin against the bore.
  • Remove wet clothing / dry the skin; watch ECG & pulse-ox cables.
Immobilise & comfort

Immobilisation & comfort

  • Pads, straps, foam wedges to reduce motion — comfortable patients hold still.
  • Support lumbar spine, knees, neck; blanket for warmth (cold → shivering → motion).
  • Call bell / squeeze-ball in hand and explained before the door closes.
Hearing

Ear protection (acoustic noise)

  • Gradient switching can exceed 99 dB(A). Ear protection is mandatory every patient, every sequence.
  • Ear plugs AND/OR MR-safe headphones, fitted correctly. Extra care in children & the sedated.
  • Accompanying persons in Zone IV also need hearing protection.
Final checks

Before you leave the room

  • Landmark set, coil connected & over anatomy, padding in place, cables straight.
  • No skin-to-skin loops, patient off the bore wall, call bell in hand, hearing protection on.
  • Patient briefed on breath-holds / stillness / scan durations.

5 · Claustrophobia & Anxiety Management most failed scans are anxiety, not physics

Communication

Talk them through it

  • Explain the whole journey before positioning — the noise, the tunnel, how long, that you can hear/see them.
  • Two-way intercom, reassurance between sequences, the squeeze-ball is their control.
  • Calm, confident manner; never rush the anxious patient onto the table.
Positioning tricks

Prone, feet-first, mirrors

  • Feet-first entry where anatomy allows keeps the head near the bore opening.
  • Prone positioning feels less enclosing for some.
  • Prism mirror / periscope to see out; eye-mask for others.
  • Wide-/short-bore or open MRI if available; a screened companion in the room.
Sedation

Mild sedation policy

  • Sedation is a clinical / policy decision, not routine — prescription, monitoring, MR-safe equipment, recovery.
  • A sedated patient can’t report heating → extra vigilance on positioning & SAR.
  • Follow local conscious-sedation / anaesthetic protocols and fasting rules.
Paediatrics

Play prep for children

  • Play specialists, mock scanners, video goggles / music, parent present (screened).
  • Feed-and-wrap for infants; “listen to the space-ship noises” framing.
  • Good prep reduces the need for GA and repeat scans.

6 · Emergencies in Zone IV the rules are counter-intuitive — know them cold

⚠ Cardiac arrest in the magnet: REMOVE THE PATIENT FROM THE MAGNET ROOM. Do the initial check, then get the patient out to a safe area (Zone III/II) and run the arrest there. NEVER bring a ferromagnetic crash cart, defibrillator or O₂ cylinder into Zone IV — they will fly into the bore and kill someone.
Arrest

Cardiac / medical arrest

  • Call for help, hit the emergency alert. Start basic manoeuvres, then evacuate the patient out of Zone IV onto an MR-safe trolley to the designated resus area.
  • Crash team & ferromagnetic kit stay outside Zone IV.
  • Know your arrest pathway and the location of MR-safe/conditional resus equipment.
Quench

Quench — what it is & what to do

  • A quench is sudden loss of superconductivity → cryogen (liquid helium) rapidly boils off to gas.
  • Helium should exhaust outside via the quench pipe — a failure vents into the room, displacing oxygen (asphyxiation) and dropping temperature.
  • If gas enters the room: evacuate immediately, get everyone out, do NOT re-enter. Over-pressure can jam the door.
  • The emergency-run-down / quench button is a last resort (destroys the magnet, vents helium) — used only to save a life, e.g. a person pinned by a projectile.
Fire

Fire in the MR suite

  • Get the patient out; raise the alarm. Only non-ferromagnetic (MR-safe) extinguishers may enter Zone IV.
  • Fire crews must be told the magnet is always on and briefed before entry; the magnet may need quenching by trained staff for safe entry.
Contrast reaction

Contrast reaction

  • Recognise anaphylaxis / acute reaction early; remove the patient from Zone IV to manage it with emergency drugs and monitoring (which live outside the magnet room).
  • Have the contrast-reaction pathway, weight-based doses and trained support to hand.

7 · Acoustic Noise, SAR / Heating & Monitoring the physics that touches the patient

Noise

Acoustic noise

  • Rapidly switched gradients vibrate → loud knocking/buzzing, worst on EPI/DWI, fast GRE, high-resolution sequences.
  • Ear protection every time; note cumulative exposure on long studies; consider quiet-sequence options if available.
SAR

SAR / heating

  • SAR (specific absorption rate, W/kg) measures RF energy deposited as heat. The scanner limits SAR by patient weight — enter the correct weight.
  • Higher field, high-flip-angle FSE/TSE, short TR, many slices → higher SAR. The system may extend TR or drop slices to stay within limits.
  • Prevent RF burns (Section 4) — SAR limits protect whole-body heating, not local hot-spots from loops/contact.
  • Watch febrile, pregnant, sedated, neonatal and impaired-thermoregulation patients closely.
Monitoring

Physiological monitoring

  • Only MR-conditional monitoring (ECG, SpO₂, NIBP, capnography) in Zone IV; route cables to avoid loops & skin contact.
  • Maintain visual + audio contact; the squeeze-ball is the patient’s alarm.
  • For sedated/unstable/ITU patients, ensure trained staff and MR-safe equipment throughout.
Key references & further reading: American College of Radiology, ACR Manual on MR Safety (2024) & Greenberg TD et al., “ACR Manual on MR Safety: 2024 Update and Revisions,” Radiology 2024 (doi:10.1148/radiol.241405). MHRA, Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use. Institute for Magnetic Resonance Safety, Education, and Research (IMRSER / Shellock R&E). Westbrook & Talbot, MRI in Practice, 5th ed (Wiley, 2018). IEC 60601-2-33 operating-mode / SAR limits. Always defer to each device’s manufacturer IFU and your local MR Safety Officer / MR Medical Director. Educational content — not a substitute for departmental policy.