Swiss Rolls get a new image

A novel magnetic material developed by British researchers may lead to dramatic improvements in the performance of Magnetic Resonance Imaging (MRI) systems.

Known as microstructured magnetic materials and dubbed ‘Swiss rolls’ by Imperial College researcher John Pendry, they help obtain images by guiding radio-frequency magnetic flux from the body to the receiver coils of an MRI scanner with very little leakage.

To demonstrate the potential of the new material, the team from Imperial College, the Medical Research Council and Marconi Caswell, placed their ‘Swiss rolls’ between the object they were trying to image – a researcher’s thumb – and a small receiver coil in a standard MRI device.

In control experiments where the Swiss rolls were replaced by a piece of inert plastic, the thumb was not detected with the small coil. But with the Swiss rolls in place, helping to direct the radio-frequency magnetic flux from the thumb to the receiver coils, a clear image of the thumb’s internal structure resulted.

The researchers claim that the new class of materials shows great potential to optimise existing MRI scanners, which are used extensively in hospitals around the world. Exploiting this class of materials could fundamentally change existing approaches to magnetic resonance imaging and spectroscopy.

The special properties of the flux-guiding device were formed by winding sheets of aluminised Mylar film, about 50 micrometers thick, around a cylindrical rod of Glass Reinforced Plastic. The aluminised Mylar film has an insulating backing which prevents any electrical contact between the layers of film. Nineteen of these bundles were arranged in a closely packed hexagonal array to form the bulk test material.

A complete technical description of the material is available at http://www.sst.ph.ic.ac.uk/photonics/pdf/mripap.pdf.

This research itself was the result of a collaboration between researchers in the department of physics at Imperial College, Marconi Caswell, and the Medical Research Council Clinical Sciences Centre, a division of Imperial College School of Medicine. It was jointly funded by Marconi Medical Systems and Marconi Caswell.