Warning on longer exposure to tomography

Study into health impact of MRI

Wednesday, 21 May 2008 12:44 UK
http://news.bbc.co.uk/1/hi/health/7412563.stm


Experts are to investigate whether magnetic resonance imaging (MRI) scanners can damage health.

The Health Protection Agency (HPA) study is likely to focus mainly on the impact on health workers who regularly operate the machines.

MRI scans have been hailed as a significant step forward in the diagnosis of medical conditions.

But there is concern exposure to the magnetic fields they create may produce adverse long term health effects.

Sir William Stewart, HPA chairman, said: "MRI scanning has some undoubted benefits in medicine, especially as an aid to accurate clinical diagnosis.

"However we need to bear in mind that the magnetic fields produced by the machines are quite substantial and that these fields are increasing in order to achieve improved clarity of image.

"The exposures to patients and medical staff from the magnetic fields can be high and there is a shortage of information on possible adverse long term health effects."

The announcement follows a recommendation by an independent board of experts, which said there was a pressing need to investigate whether regular exposure to the magnetic fields produced by MRI scanners could raise the risk of cancer and other diseases.

Clear images

MRI, first developed 30 years ago, is based on a well established scientific technique, nuclear magnetic resonance, which uses the interaction of magnetic fields with the spin of the nuclei of atoms to provide detailed information on the constituents of chemicals and biological materials.

The technique can provide excellent, detailed images of the body's soft tissue and is an alternative to using X-ray techniques such as computed tomography (CT).

MRI does not use ionising radiation and this can be a distinct advantage for examinations of children or for abdominal examinations where radiation doses can be high.

However, MRI requires large magnetic fields for successful scanning - bigger than those commonly used in industry.

The European Parliament was due to vote on new rules to limit exposure to powerful electromagnetic fields earlier this year.

But following advice from doctors, who said the proposed limits were so low they could prevent the use of MRI scanners, the issue was placed on the back burner.