Keeping an eye on pre-scan metal detection

The NHS is poised to test adapted mine detection technology as a way of checking for tiny pieces of metal in patients’ eyes.

The UK National Health Service (NHS) is poised to test adapted mine detection technology as a way of checking for tiny pieces of metal in patients’ eyes.

A handheld device called MagPeye will be used to find microscopic metallic fragments in the eyes of patients about to undergo MRI scanning. If missed, these can cause injury during the MRI procedure itself.

Roke Manor Research, a Hampshire-based R&D division of Siemens, built MagPeye by refining ultra-sensitive metal detection technology originally developed for mine clearance systems.

MagPeye radiates an extremely low-power electromagnetic field over a narrowly-defined search range. It is able to detect fragments smaller than 0.1mm3 at a distance of 5cm and to distinguish between ferromagnetic and non-ferromagnetic fragments.

Pre-screening for metal in the body is a vital part of the MRI process, as the powerful magnetic field generated by the scanners can cause injury by shifting unidentified material.

The eyes have long posed a problem for radiologists. Currently they have to screen patients via a lengthy questionnaire, often backed up an x-ray, which delays the scan, adds to costs and exposes the patient to unnecessary x-ray radiation. By using MagPeye the results are instant, allowing patients to proceed through the MRI process immediately.

Colin Richardson, a principal consultant engineer at Roke Manor, said delays caused by checks for metal in the eyes and the resulting x-rays are believed to cost the NHS millions of pounds a year.

‘It is important to know the whereabouts of any metal in the body before a scan. What we have developed has the required sensitivity to do the job but is extremely cost-effective and convenient to use.’

Roke Manor eventually hopes to apply similar technology to handheld devices suitable for other specialist applications, such as detection of concealed syringe needles.

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