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Iseult Project

Travel of the largest and most powerful MRI magnet in the world

On Thursday, May 4, a giant magnet weighing 130 metric tons left the assembly plants in Belfort on its journey to the NeuroSpin research facility at the CEA's Paris-Saclay Center (Essonne). The cutting-edge magnet, which will generate a magnetic field of 11.7 tesla[1], is the core component of the most powerful MRI (Magnetic Resonance Imaging) scanner in the world to be used for human brain imaging. To make such a powerful magnet, CEA research engineers had to design an instrument larger than any other. Before it can be placed under the structure awaiting it at NeuroSpin, this magnet will travel several hundred kilometers, by road, sea and inland waterways. It arrived in Saclay on May 18 2017.

Published on 2 May 2017

The story of this giant magnet began back in 2000, at the CEA, with the project to build a high-field neuro-imaging research center, NeuroSpin, which would become home to the 11.7 T magnet, and be used for exploring the human brain. This project was the brainchild of physicists, biologists and neuroscientists. It is the core component of an MRI scanner unlike any other which, thanks to its high magnetic field, will be used to obtain brain images a hundred times more detailed than current imaging machines, used in hospitals, which produce a magnetic field of 1.5 T or 3 T. 

An instrument larger than any other

Producing this magnet, which is five meters long, five meters in diameter, and weighs over 130 metric tons, has been an incredible feat. CEA research engineers working at the Institute of Research into the Fundamental Laws of the Universe (CEA-IRFU), had to use all their inventiveness to design a coil in which such a powerful current can circulate, of around 1,500 amperes, thereby generating a magnetic field of 11.7 T. The only way such high strength can be attained is to use the physical properties of superconductivity. To this end, 182 kilometers of niobium-titanium alloy superconducting wire are wound in 170 "double pancake" coils. These are then assembled to form a "tube" with a 90 cm diameter opening, within which the magnetic field will be 11.7 T. The space inside the magnet is large enough to enable whole-body imaging. 

The CEA engineers also had to create a winding system that generates an opposing field to confine the main magnetic field inside the examination room. These windings, known as active shield coils, surround the main magnet and limit the zone of exposure to the magnetic field to a few meters around the MRI machine.

Since superconductivity is involved, the material used must be continuously cooled to a temperature as close as possible to absolute zero (0 K) to ensure that the current can flow without friction or heating up. The magnet for the Iseult project[1] is maintained at 1.8 K (i.e. –271.35°C) using a superfluid liquid helium bath.   


VideoLes super-aimants

Designing this magnet has drawn on the expertise of CEA-IRFU research engineers and their experience in developing magnets for large-scale instruments in the field of high-energy physics, such as accelerators and particle detectors (e.g. the ATLAS detector at the CERN's Large Hadron Collider) and experimental nuclear fusion reactors (e.g. the West reactor at Cadarache). 


The magnet's journey from Belfort to Saclay

Given the magnet's great size and weight, as well as to minimize vibration, most of the journey will be made by sea and waterways. The convoy will leave the assembly plants in Belfort on May 4 and travel by road to Strasbourg where it will be transferred to a barge. It will then head up the Rhine River to the Port of Rotterdam in the Netherlands, where it will be loaded onto a ship and sail to Le Havre. It will then again be loaded onto a barge and taken up the Seine as far as Corbeil-Essonnes. The final stage of the journey to Saclay will be by road.    

What is MRI? 

Magnetic Resonance Imaging (MRI) is used to obtain 2D or 3D images of soft tissue (e.g. muscles or the brain). It is based on the magnetic properties of hydrogen nuclei present in water molecules in the human body. Once a patient is placed in the MRI machine, hydrogen atoms behave like magnets and align themselves in the direction of the magnetic field. The antenna placed over the area of the body being studied can be used to change the orientation of the atoms which, as they return to their initial position, emit a radiofrequency signal in the form of a wave. The images obtained are based on these signals, which provide information on the nature of the body tissue. MRI is a non-invasive technique and does not require the use of a radioactive source, unlike x-rays and scanners. 


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MRI at 11.7 T and what it may tell us about the brain

Apart from the incredible technological challenges involved in building this high-field MRI machine, it also promises to help us make major advances in the neuroscience and medical research. The higher resolution of the MRI images obtained will be invaluable in improving what can be observed and, therefore, how much we can learn about the workings of the brain. Below is an example of a study on the hippocampus, the area of the brain 

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As for anatomical images, observation of the areas involved in other neurodegenerative diseases, such as Parkinson's, will be improved and thus enable earlier diagnosis. Very high-field MRI will also produce more precise images of the brain structures and networks involved in cognitive function (speaking, reading, etc.) in healthy subjects, which will improve our understanding of brain dysfunction that causes, for example, psychiatric disorders such as schizophrenia and autism. 

NeuroSpin: a large-scale facility for high-field neuro-imaging

 NeuroSpin, the neuro-imaging center for very high magnetic field Nuclear Magnetic Resonance Imaging (nMRI), is a major research facility opened in 2007 with a view to pushing the current limits of brain imaging as far as possible. The new level of performance will make it possible to observe the brain and its pathologies with extreme precision, at a scale more representative of brain processes at cellular and molecular level. NeuroSpin brings together physicists specializing in MRI and MEG (magnetoencephalography), experts in signal processing and data processing, neurobiologists and doctors, all in one place. NeuroSpin is part of CEA's Fundamental Research Division, within the Institut Joliot.


IRFU, Institute of Research into the Fundamental Laws of the Universe

IRFU carries out scientific and technological research, spanning three disciplines: Astrophysics, Nuclear Physics and Particle Physics, together with all the related technical departments. These three disciplines have many experimental methods in common because exploring the Universe, whether on the very small or the very large scale, relies on radiation detection. IRFU is part of CEA's Fundamental Research Division.

[1] The tesla is the SI unit for magnetic field strength. Compare this with the Earth's magnetic field in Paris, which is 0.00005 T. 

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