Magnetic resonance imaging (MRI), already an very effective technology, could soon become even more precise. The MCube H2020 project is working toward more accurate diagnoses.
We tend to forget that magnetic resonance imaging (MRI) is one of the greatest technological advances of the past thirty years. Implementing it wasn’t easy given the many complex physical phenomena involved. Generating an MRI requires two steps inside a tunnel:
- creating a static magnetic field that magnetises the proton in the nucleus of hydrogen atoms present throughout the human body;
- creating a high-frequency electric field, which stimulates each magnetised proton to spin like a top and emit a signal commensurate with the density of its surrounding tissue. The signal is measured and ‘translated’ into an image from which an anomaly, such as a tumour, can be spotted.
‘It’s a fantastic machine that generates precise images. Creating it required the input of experts in many fields’, explains Christophe Craeye, who leads the ‘aerial team’ at the Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM).
High-value magnetic fields
But researchers are never satisfied. An international team of scientists is forging ahead to make MRIs even more precise. To do so, the H2020 MCube project aims to make MRIs function at higher values of the magnetic field. ‘In principle, the stronger the magnetic field, the greater the resolution and sensitivity, but in practice it’s not so simple, because if we increase the magnetic field’s value, we also have to increase the strength of the electric field. This produces a wavelength comparable to the tunnel’s diameter, which results in standing waves that are reflected by the tunnel walls and distort the reception of proton signals.’ It also results in a distorted image.
The solution: metamaterials
Committed to overcoming this problem, project scientists turned to metamaterials. ‘These materials, which don’t exist in nature, have a structure that gives them interesting properties, such as the negative refractive index and the collimation effect, which can prove useful to MRIs.’
Today, three potentially relevant metamaterials exist:
- linear metamaterials;
- surface metamaterials;
- mass density metamaterials
‘We don’t yet know which are best for MRIs, so that’s the first thing we have to determine, then we’ll concentrate on those with the greatest potential. Our goal is to arrive at a medical application by the project’s end in four years.’
More precise images
Prof. Craeye’s team is responsible for volume metamaterials research. ‘Our work focuses on their value in terms of their negative refraction and collimation effect. The latter, for example, allows for measuring areas with a weak magnetic field, which in turn allows for using amplifiers most appropriate to the signal. These are made of metallic components that interfere with the magnetic field; in standard MRIs, the field is strong, resulting in a poor-quality image. In a weaker magnetic field interference decreases, resulting in a sharper image.’ The project is a collaboration between Utrecht University, the Institut Fresnel (Marseille), the French Alternative Energies and Atomic Energy Commission (Commissariat à l'énergie atomique et aux énergies alternatives, CEA, Paris) and Saint Petersburg University.
A glance at Christophe Craeye's bio
1994 Master’s Degree in Civil Electrical Engineering, UCL
1998 Doctorate, specialised ocean radar observation radar (UCL, collab. ESA, NASA), UCL
1999-2001 Research Fellow, TU/Eindhoven (NL), ASTRON (NL), Univ. Massachusetts (USA),
Square Kilometer Array radio telescope project
2002- 2009 Associate Professor, UCL, creation of ‘aerial team’ (digital methods, beam formation, metamaterials)
Since 2009 Professor (same subjects), UCL