Medical Imaging With "Swiss Rolls"

Writing in the journal Science today they describe initial experiments confirming the exotic nature of the material produced.

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.

The crucial feature of the material is that it consists of a periodic array of structures each of which is much smaller than the wavelength of the radio-frequency fields it operates with.

To demonstrate the potential of the new material, the team from Imperial College, the Medical Research Council and Marconi Caswell Ltd., 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,” they write.

The idea of using microstructured magnetic materials in a swiss roll structure came to the research team when they examined the potential of ‘photonic band gap’ materials.

Such materials can manipulate electromagnetic radiation of a certain frequency band and prevent it escaping from the material in any direction.

Materials that can manipulate radio-frequency magnetic flux, but do not disturb static or audio frequency fields are ideal for MRI systems, which require highly uniform static fields in order to produce undistorted images.

Conventional magnetic materials affect both static and radio-frequency fields, so that they cannot be used to manipulate radio-frequency flux without degrading image quality.

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

The research was jointly funded by Marconi Medical Systems and Marconi Caswell Ltd.