Supra-linear SNR Gain with Surface Receive Coils

Magnetic resonance imaging (MRI) has long been used to investigate the human brain, but as researchers continue to push the boundaries of current MRI applications, there is a push for ultra-high field instruments that will provide deeper insights. Advanced human brain research is supported by a rise in field strengths of MRI instruments. With 7 Tesla (T) now being a standard field strength for ultra-high field MR in humans, the industry is seeing demand for instruments operating at 9.4 T or above, driven by the hunger for an even greater gain in intrinsic signal-to-noise ratio (SNR).

While this SNR demand exists, other parameters that are affected by field strength must be considered. To investigate this, researchers from the Max Planck Institute for Biological Cybernetics in Tübingen, Germany and the Otto-von-Guericke University in Magdeburg, Germany compared the impact of magnet strength on parameters such as relaxation times, B1 homogeneity, and parallel imaging g-factor using 3 T, 7 T, and 9.4 T.

The Ultra-high Field Advantage 

In addition to the expected increase the longitudinal relaxation time, T1, and the decrease of T2 and T2*, their results show experimental evidence of a supralinear increase in SNR with field strength pared with a g-factor that did not decrease as expected. This supralinear SNR increase and lack of g-factor decrease are attributed to the coils that were chosen for this study design. For reception, multi-channel surface coils were employed and the authors propose that these positive SNR and g-factor outcomes are a result of this coil selection. With ideal coil choice, the advantages of ultra-high field MRI can even be compounded.

Read the full paper here.

Pohmann R, Speck O, Scheffler K. Signal‐to‐noise ratio and mr tissue parameters in human brain imaging at 3, 7, and 9.4 tesla using current receive coil arrays. Magnetic Resonance in Medicine. 2015;75(2):801-809. doi:10.1002/mrm.25677.