scholarly journals First measurements of surface nuclear magnetic resonance signals without an oscillating excitation pulse – exploiting non‐adiabatic prepolarization switch‐off

2021 ◽  
Author(s):  
Thomas Hiller ◽  
Stephan Costabel ◽  
Raphael Dlugosch ◽  
Mike Müller‐Petke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Excitation Pulse ◽  
Nuclear Magnetic

Optimal Broadband Pulse Design with Limited RF Amplitude in Nuclear Magnetic Resonance

2014 ◽  
Vol 543-547 ◽  
pp. 2288-2291
Author(s):  
Shu Lin Zhang ◽  
Yan Chang ◽  
Xiao Dong Yang
Keyword(s):  
Optimal Control ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Optimal Control Theory ◽  
Excitation Pulse ◽  
Design Criteria ◽  
State Transfer ◽  
Shaped Pulse ◽  
Broadband Pulse ◽  
Nuclear Magnetic

In this paper, we introduce an optimal control theory (OCT) based method for design of broadband excitation pulse with limited radio frequency (RF) amplitude in nuclear magnetic resonance (NMR). The capability of the optimized pulse was verified by the following design criteria: the state transfer of 1H fromtoover resonance offsets of, the pulse duration is 1ms with maximum RF amplitude of 10 kHz. The simulation result demonstrates that the optimal control-based shaped pulse is much more adaptable to broadband excitation, providing a better performance than traditional hard pulse.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

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