Shelan Mahmood Nov 2, 2026

When the Power Goes Off: Electrical Installation Safety in Nuclear Medicine and Diagnostic Radiology

Electrical installations are rarely the first thing we think about in radiation protection, but they deserve more attention. Over the past year, three developments have come together that every nuclear medicine and diagnostic radiology service should be aware of:

  • A coroner's Prevention of Future Deaths report following a patient death in 2020, where mains power to an interventional X-ray system was lost during a coronary procedure.
  • AXREM (the trade association for imaging equipment suppliers) publishing new guidance, Medical Device Installation Safety, and Version 2 of its Electrical Installation Checklist (April 2026).
  • BS 7671:2018+A4:2026 (IET Wiring Regulations), published in April 2026, which includes an extensive rewrite of Section 710 – Medical Locations.

What happened

During a coronary procedure, mains power to the X-ray system was lost as the radiographer moved the C-arm and table into the CPR position. Staff could not restore power from the room: the only "on" button was in a plant room outside the suite, and there were no status indicators showing the state of the mains contactor. It took around seven minutes to restore power and a further five minutes for the system to reboot. The cause was not conclusively established, although a faulty emergency power off (EPO) contact was found on testing.

Ian Chell MSc FSRP, who acted as an independent expert in medical locations, has written about the lessons learned for the Society of Radiographers and contributed to both AXREM documents.

What AXREM has published

Medical Device Installation Safety sets out the demarcation of responsibilities. The equipment supplier is responsible from the mains connection point onwards. Everything before it – the mains supply, UPS and batteries, switchgear, EPO circuits, indicators and the room environment – is the responsibility of the "responsible organisation", that is, the hospital or clinic. This remains the case after the warranty period, even for turnkey projects.

The Electrical Installation Checklist is intended for permanently installed equipment such as X-ray, CT and MRI. Suppliers are expected to ask the customer to complete and sign it before installation. The customer declaration states that clinical use of equipment in a non-compliant installation is at the customer's risk, and any departures from BS 7671 must be declared.

Why this matters in nuclear medicine

Nuclear medicine departments are not always considered alongside interventional suites, but several points apply directly:

  • Hybrid imaging: SPECT/CT and PET/CT systems include a permanently installed CT scanner, so the checklist applies – dedicated supply, line impedance, BS EN 61439 control panels, EPO arrangements, remote ON/OFF controls with power indication, and entrance warning lights.
  • Power loss mid-study: the patient has already been administered a radiopharmaceutical. With short-lived PET tracers, a lost scan often cannot be recovered on the day, and a repeat study means a further administration and additional patient dose, which must be justified under IR(ME)R. Contingency arrangements for power failure should be part of departmental planning.
  • Environmental conditions: gamma camera and PET detectors can be sensitive to temperature changes, and UPS batteries degrade if kept above around 25 °C. AXREM is clear that cooling, airflow and humidity sit with the responsible organisation and need periodic maintenance.
  • Radiopharmacy and hot lab: these are outside the scope of the AXREM documents, but the same thinking applies. Isolators, fume cupboards, extract systems and radiation monitors depend on a reliable supply. It is worth confirming what happens to containment and monitoring during a power failure, and how staff are alerted.

Why this matters in diagnostic radiology

  • Interventional and fluoroscopy rooms: IEC 60601-2-43 requires indication of emergency power supply status in the examination room. AXREM recommends separate indicator lights for mains, UPS and system power, so staff can tell whether an EPO has been operated.
  • CT and general radiography: dedicated supplies and low line impedance are needed to achieve full generator output. A shortfall may show up as poor image quality or equipment errors rather than an obvious fault.
  • Lower-power equipment (intraoral dental, OPG, DEXA): these may use a manual switch, such as a double-pole switched fused spur, instead of a contactor. The checklist states that the switch location should be approved by the local RPA.
  • Equipment replacement: AXREM advises that EPO buttons, contactors, relays and control panels should not be reused when equipment is replaced, as their reliability cannot be assured.

Where the RPA fits

This is the first time a supplier's electrical installation checklist has explicitly referenced the local RPA. Two items are relevant:

  • Approval of the switch (disconnector) location for low-power X-ray equipment such as dental and DEXA.
  • Approval of entrance radiation warning lights, including their suitability for the expected on/off frequency. The checklist also asks that warning light circuits are RCD protected and not derived from the supply feeding the medical equipment.

A practical point on terminology: "disconnector" is the agreed term for the isolating device, covering switched fused spurs and contactor switchgear. Using the same term as the electrical design team avoids confusion when commenting on drawings.

Legal requirement, good practice and recommendation

Legal requirement

  • IRR17: the RPA must be consulted on the prior examination of plans for installations (regulation 14 and Schedule 4), and suitable warning devices are expected where X-ray equipment is used (regulation 9 and the Approved Code of Practice, L121).
  • The Electricity at Work Regulations 1989, PUWER 1998 and the Health and Safety at Work etc. Act 1974 apply to the electrical installation and its maintenance.
  • IR(ME)R 2017: any repeat exposure following an equipment failure must be justified.

Good practice

  • BS 7671 (currently Amendment 4:2026), including Section 710. BS 7671 is not itself statutory, but is the accepted means of demonstrating a safe electrical installation.
  • HTM 06-01 (England) or SHTM 06-01 (Scotland) for NHS sites, including an Electrical Safety Group.
  • The AXREM guidance and checklist.

Recommendation

  • Involve estates, clinical staff, clinical engineering, the supplier and the RPA from the earliest design stage.
  • Train operators on mains ON/OFF controls, EPO reset and UPS indicators, and include this in local procedures.

Practical steps for imaging services

  1. Share the AXREM guidance and checklist with estates and project leads for any planned installation or equipment replacement.
  2. Specify compliance with the current edition of BS 7671 in project and installation contracts.
  3. Check where mains ON/OFF controls and status indicators are located, and whether staff can restore power from the control or examination room.
  4. Confirm EPO buttons are clearly labelled, shrouded where appropriate, and distinct from equipment motion stop buttons.
  5. Ask the RPA to review the disconnector location and warning light arrangements at the plans stage, not at the critical examination.
  6. Include the electrical installation, UPS and environmental systems in planned maintenance, not just the imaging equipment.
  7. Make sure staff know how to report faulty indicator lights or switchgear, and that these are fixed promptly.

Final thoughts

This incident is a reminder that patient safety depends on the room as well as the equipment. For RPAs, the change is modest but significant: our input on warning lights and isolation points is now written into the supplier's checklist. For services, the message is to involve the right people early and not to assume an existing installation is suitable for new equipment simply because it was compliant when built.

References

TAGS Diagnostic Radiology, Interventional radiology, IRR17, Medical Imaging, Nuclear Medicine, Patient Safety, PET/CT, radiation protection , Radiation protection advisor, AXREM, BS 7671, Electrical installation

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