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11.7-tesla MRI: the Iseult magnet is fully operational

​At the CEA-Joliot's NeuroSpin neuroimaging center, the Iseult project's 11.7-tesla MRI produced its first images in September 2021, thanks to the extraordinary magnet developed by the CEA-Irfu. Read on for a look at the origins behind this world premiere.

Published on 10 November 2021

​The Iseult MRI has the most powerful superconducting electromagnet in the world, and the first to break into the high-availability category with an autonomy of ten years!

  • It weighs 132 tons, and measures 5 meters in length by 5 meters in diameter. An entire body can be imaged thanks to its central opening of 90 centimeters.
  • It is powered by a current of 1,500 amperes and permanently cooled with superfluid helium to 1.8 kelvin (-271.35°C). At this temperature, the conductor of the niobium-titanium alloy magnet is superconducting and carries a very large current without heating.
  • It includes a set of 170 coils creating the main magnetic field and two shielding coils minimizing the magnetic field outside the magnet. In total, there are 182 kilometers of superconducting wire!
  • It is equipped against power cuts and computer network failures, and has a cooling autonomy of seven days. Its protection is ensured by an automatic system.
2021: The first images

In March 2021, the magnet celebrated its second anniversary at 1.8 K without any interruption in service. This feat, remarkable for such a complex installation, has been recognized worldwide. In recent months, the teams have been testing the reliability of the cryogenic and electrical installations and preparing for future operations.

  • In particular, they have studied the impact of gradient coil operation, which can induce cryogenic losses and electrical voltages within the coils. This can result in a rapid discharge of the magnet that is supposed to protect the main magnet, and a potential shutdown of the installation for several months in order to get it back in service.
  • The effects of road traffic near the building and of external electromagnetic waves were also studied to confirm the effectiveness of the filtering systems developed specifically for the magnet.

 In July 2021, experts from Siemens brought the MRI into operation. A first MRI signal confirmed that the main magnet and its gradient coil work. The magnet has the required spatial homogeneity: 11.72 ± 0.00000293 teslas.

In September 2021 the first images of a pumpkin were obtained.

2019: A nominal field strength of 11.7 teslas is achieved in record time

In 2019, the increase in current used to reach the nominal magnetic field of 11.7 teslas was a world record. In fact, it required no more than five hours, instead of the several days needed for hospital MRI magnets.

 Previously, the 1,300 or so procedures intended to offset the appearance of potential defects had to be tested and validated, one after the other. 

2018: The first cool-down to 1.8 kelvin begins

The first cool-down of the magnet from room temperature, which began at the end of 2018, lasted 14 weeks. It required 250,000 liters of liquid nitrogen and 18,500 liters of liquid helium. 

2017: The delivery odyssey

After a highly exceptional five-week journey from Belfort to Saclay, the magnet was finally delivered to NeuroSpin in 2017. It took two more years for the teams to connect the magnet, installed in its arch, to all of its auxiliary equipment and to prepare for its commissioning. 

2010: The Irfu design is approved and the magnet manufacturing begins

In 2010, the design conceived by Irfu physicists, in collaboration with a handful of industrial and academic partners, was approved by a committee of international experts.

 Manufacturing of the magnet began in 2010 at Alstom (acquired by General Electric in December 2015) in Belfort, in close collaboration with CEA teams (weekly visits by members of the Irfu project team and the permanent presence on site of an Irfu representative for nearly six years).

 In parallel, the installation of a cryogenic plant and auxiliary equipment necessary for the operation of the magnet were prepared at NeuroSpin. The control-command systems, automatic systems, power supplies, and all of the cryogenic equipment were individually tested once they were in place. 

2004: The Iseult project to build a very high field MRI is launched

The Iseult project was launched on April 30, 2004 with the signing of a Franco-German agreement by President Chirac and Chancellor Schröder to develop molecular imaging by very high field MRI.

An international call for bids was launched for a technical feasibility study of the magnet, the central component of the imaging apparatus. Irfu, which has internationally recognized expertise in the construction of superconducting magnets (as demonstrated by its major contribution to the LHC magnets at CERN), was the sole respondent. After a long study phase, numerous prototypes were built and tested in order to develop and validate the technological developments necessary to create this exceptional instrument.

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