Medical imaging with ‘Swiss Rolls’

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

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. (see notes to editors 1).

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.

For further information please contact:

Judith Moore Press Office Imperial College, London Tel: 44-0-20-7594-6702 Email: j.h.moore@ic.ac.uk

Notes to Editor:

Title: Microstructured Magnetic Material for RF Flux Guides in Magnetic Resonance Imaging.

Journal: Science Vol. 1291 No. 5505 - 2 February 2001

Authors: M.C.K. Wiltshire (a), J.B. Pendry (b), I. R. Young (b), D.J. Larkman (c) D.J Gilderdale (c), J.V Hajnal (c).

a) Marconi Caswell Ltd, Caswell, Towcester, Northants, NN12 8EQ

b) Department of Physics, Imperial College of Science, Technology and Medicine, Prince Consort Road, London SW7 2AZ.

c) Robert Steiner MR Unit, Clinical Science Centre, Imperial College School of Medicine, Hammersmith Hospital, Du Cane Road, London, W12 0HS, UK

1. 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.

2. Marconi Caswell Technologies is part of the exciting new optical components business created within Marconi plc. The new business brings together Essex based Marconi Applied Technologies and Marconi Caswell Technologies based in Northamptonshire. The organisation has the pace and edge of a start up operation but the credibility, technology portfolio and operational infrastructure of an established player. Marconi's optical components business brings together unique capabilities in materials sciences and in the design and development of optical components, which will be supported by expanded production capacity for optical amplifiers and active optical devices.

   Marconi Applied Technologies:
   Created in 1947, the Company provides innovative leading edge technology products. Currently employing 1400 people in the UK, the Company has annual sales exceeding UKP86.5M, of which 65 per cent is exported through wholly owned companies in the USA, France and a network of world-wide distributors. The Company designs and manufactures high technology products in areas of electro-optical products, RF power and microwave devices. It is a key supplier of strategic components into markets such as Space, Communications, Medical, Science, Commercial Sensing and Defence. The Company recently announced a major investment to establish a research and development group and volume manufacturing facility for optical amplifiers, which is already operational.

   Marconi plc is a global communications and IT Company with 49,000 employee worldwide and sales in over 100 countries. It supplies advanced communications solutions and the key technologies and services for the Internet. www.marconi.com

3. The Medical Research Council (MRC) is a national organisation funded by the UK tax-payer. Its business is medical research aimed at improving human health; everyone stands to benefit from the outputs. The research it supports and the scientists it trains meet the needs of the health services, the pharmaceutical and other health-related industries and the academic world. MRC has funded work which has led to some of the most significant discoveries and achievements in medicine in the UK. About half of the MRC’s expenditure of UKP345 million is invested in over 50 of its Institutes and Units, where it employs its own research staff. The remaining half goes in the form of grant support and training awards to individuals and teams in universities and medical schools. Web site at: http://www.mrc.ac.uk

4. Imperial College of Science, Technology and Medicine is an independent constituent part of the University of London. Founded in 1907, the College teaches a full range of science, engineering, medical and management disciplines at the highest level. The College is the largest applied science and technology university institution in the UK, with one of the largest annual turnovers (UKP330 million in 1998-99) and research incomes (UKP173 million in 1998-99). Web site at: http://www.ic.ac.uk