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Scientific result | Article | MRI
A collaboration led by a METRIC team (BAOBAB/NeuroSpin) has undertaken to measure the signal-to-noise ratio (SNR) in MRI at the centre of a spherical phantom at different magnetic field strengths (B0). Their data confirm the theories that SNR increases with approximately the square of B0.
MRI scanners with very high magnetic fields (B0 > 7 Tesla) for humans are becoming increasingly common around the world. The most powerful to date (nominal field of 11.7 T) is at NeuroSpin. Exploiting these high fields for biomedical research requires, among other things,
understanding and quantifying the expected gains in signal-to-noise ratio (SNR)
and contrast-to-noise ratio (CNR)
Calculations and simulations have been developed over the years
to determine what gains can be achieved with increasing B0. However, to date, no experiment has been able to evaluate the contribution of B0 to SNR alone.
In a study carried out in collaboration with the universities of
Minnesota, the METRIC team of
BAOBAB (NeuroSpin department)
measured the SNR at the centre of a single spherical phantom in different devices, at several field strengths: 3 T, 7 T, 9.4 T, 10.5 T and 11.7 T. The set-ups and experimental conditions were all otherwise almost identical (antennas, electrical properties and MRI sequence protocols). The researchers
compared their data with expected theoretical values (ultimate intrinsic SNR theory).
After eliminating the influence of tilt angle excitation inhomogeneity, the measurements revealed that
the SNR increase is a function of
B01,94±0,16, a value reasonably close to the theoretical value of B02,13.
As the ultimate intrinsic SNR is a measure of the performance of a radio frequency antenna, this result will help to determine the available room for improvement.
Caroline Le Ster, next to NeuroSpin's 3T MRI scanner and holding the phantom used to measure and compare the signal to noise ratio between different MRI scanners during the study. © NeuroSpin/CEA
Le Ster, Andrea Grant, Pierre-François Van
deMoortele, AlejandroMonreal-Madrigal, Gregor Adriany, Alexandre Vignaud, Franck Mauconduit, Cécile Rabrait-Lerman,
Benedikt A. Poser, Kâmil U˘gurbil, Nicolas Boulant. Magnetic field strength dependent SNR gain at the center of a spherical
phantom and up to 11.7T. | Magn. Reson. Med.,
2022 DOI: 10.1002/mrm.29391
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.