Figure 3: 7T clinical MRI manufactured by Siemens Healthcare with a table of its main technical specifications | MAIN FEATURES
|
Operating frequency | 298 MHz |
Magnet inner diameter
| 60 cm |
B0 shielding
| passive
|
Gradient strength
| 50 mT/m |
Gradients slewrate | 333 (T/m)/s |
In 2008, NeuroSpin's 7T MRI has been the first scanner of its kind installed in France (Figure 3). The magnet passive shielding is made of third hundred tons of steel set around the system (Figure 4). It has been manufactured by Siemens Healthcare and runs under SyngoMR VB17 user interface.
Figure 4: A view of the clinical 7T MRI passive shielding installation.
The scanner includes two distinct radiofrequency (RF) transmission chains. One single channel RF transmitter capable to emit up to 8kW. For this mode, we have got a transceiver Circular Polarized (CP) In Vivo Corporation birdcage coil, and a Nova Medical one including a birdcage for transmission purposes and 32 channel coil array for reception (Figure 5). We own two copies to deal with potential unexpected events. A second transmission multi-channel transmission system allows to emit on 8 separate channels. To ensure a secure Specific Absorption Rate management for volunteer experiments, the system is equipped with the latest Step 2 SAR supervision system. In this mode we use RF home-mode coils and one Rapid Biomedical transceiver coil (Figure 6).
Figure 5: Nova Medical single transmission channel in transmission and 32 channel coil array in reception |
Figure 6: Parallel transmission (ptx) coils available in « Step 2 » on NeuroSpin 7T MRI : For left to right our first home-made transceiver 8Tx/8Rx, another coil developed in-house distributing 8 transmitter channels on 12 coils. For reception purposes 22 coils are used to maximize Signal to Noise Ratio. On the right side is displayed our 8Tx/8Rx Rapid Biomedical coil. |
This MRI is used in the context of clinical, neuroscientific and methodological researches. Clinical research is carried on within a close collaboration between UNIACT and UNIRS in addition with leading university hospital services specialized on neurodegenerative diseases. NeuroSpin collaborates with APHP Lariboisière, Saint Anne, La Pitié Salpêtrière, Tours University Hospital, l'ICM, … Work on neurosciences is done mainly in-house throughout an partnership between UNICOG and UNIRS. So far, methodological developments focus on optimizing RF transmission homogeneity which is the main problem of UHF MRI. For this topics we work in collaboration with CMRR a laboratory of Minnesota University headed by K. Ugurbil and Fresnel Institute in Marseille headed by S. Enoch …