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Updated: Mar 9, 2026

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy
Published on: October 9, 2020
Nuclear paramagnetism-induced MR frequency shift and its implications for MR-based magnetic susceptibility
Jinil Park1,2, Jeongtaek Lee1,2, Jang-Yeon Park1,2
1Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea.
Purpose:
To investigate the 1 H spin contribution (0.004 parts per million (ppm)) to the water magnetic susceptibility and discuss its implications for high-precision phase mapping and tissue susceptibility measurement.
Methods:
Free induction decay (FID) signals were acquired at 3 Tesla (T) and 9.4T from thin square phantoms at a range of tip angles. The FID frequency shift was examined at a high resolution ( < 0.01 Hz) for different phantom orientations relative to the main magnetic field (B0 ). B0 maps on an axial and a coronal slice of a spherical phantom were obtained at 3T to examine the tip angle and orientation dependence at the 0.001 ppm level.
Results:
A frequency shift of about 0.3 Hz was observed between tip angles of 10 ° and 90 ° when the thin phantom was normal to B0 at 3T, whereas the shift changed sign and was halved in magnitude when the phantom's face was parallel to B0 . At 9.4T, the effect size increased proportionately. The orientation-dependent frequency shift was also observed in the B0 map experiment. These observations agree with theoretical frequency shift due to longitudinal 1 H spin polarization.
Conclusion:
Magnetic susceptibility contribution from the nuclear paramagnetism should be taken into account in the interpretation of high-precision phase and susceptibility mapping in MRI. Magn Reson Med 77:848-854, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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