New applications and perspectives of fast field cycling NMR relaxometry

Abstract

The field cycling NMR relaxometry method (also known as fast field cycling (FFC) when instruments employing fast electrical switching of the magnetic field are used) allows determination of the spin-lattice relaxation time (T1 ) continuously over five decades of Larmor frequency. The method can be exploited to observe the T1 frequency dependence of protons, as well as any other NMR-sensitive nuclei, such as (2) H, (13) C, (31) P, and (19) F in a wide range of substances and materials. The information obtained is directly correlated with the physical/chemical properties of the compound and can be represented as a 'nuclear magnetic resonance dispersion' curve. We present some recent academic and industrial applications showing the relevance of exploiting FFC NMR relaxometry in complex materials to study the molecular dynamics or, simply, for fingerprinting or quality control purposes. The basic nuclear magnetic resonance dispersion features are outlined in representative examples of magnetic resonance imaging (MRI) contrast agents, porous media, proteins, and food stuffs. We will focus on the new directions and perspectives for the FFC technique. For instance, the introduction of the latest Wide Bore FFC NMR relaxometers allows probing, for the first time, of the dynamics of confined surface water contained in the macro-pores of carbonate rock cores. We also evidence the use of the latest field cycling technology with a new cryogen-free variable-field electromagnet, which enhances the range of available frequencies in the 2D T1 -T2 correlation spectrum for separating oil and water in crude oil. Copyright © 2015 John Wiley & Sons, Ltd.

Compact NMR relaxometry of human blood and blood components

“…The field dependence of T 1 , T 2 and T 1ρ offer insights into the mechanisms that contribute to nuclear spin relaxation. Some of these experiments utilize specialized hardware for fast-field-cycling NMR [9]. …”

Nuclear magnetic resonance at millitesla fields using a zero-field spectrometer

“…At present, the electromagnetic coils within the shielded chamber supply DC magnetic fields up to several millitesla, providing a means to study spin phenomena around the "crossover zone" between the regimes of dominant spin-spin coupling and Larmor precession (1-100 µT), including relaxation dispersion [36,37,38] and also parahydrogen induced hyperpolarization, [5,6,39,40,41,42,43,44,45], which is strongly influenced by field-dependent level anticrossings and could be advantageously used in ZULF NMR. In future, we expect many opportunities for multidimensional experiments that correlate spin phenomena between the two regimes and make use of the large catalog of existing high-field pulsed NMR methods.…”

Comparison of fast field-cycling magnetic resonance imaging methods and future perspectives

“…Repeating this sequence with different evolution times allows finding T 1 at the evolution field, so that repeating the overall method for different evolution fields provides a measurement of the dispersion of R 1 (an example of a 1 H R 1 NMRD profile is shown on Figure 2). As R 1 relaxation mostly depends on characteristic times of microscopic motions (such as translation and rotation) and possible energy dissipation through matching energy levels of some molecular structures (such as interactions with quadrupole nuclei), R 1 NMRD profiles give insight into the molecular dynamics and structural order of a wide range of complex systems such as organic solids, metals, polymers, liquid crystals, porous media, exogenous contrasts agents or biological systems [3][4][5][6]. While used for a long time as a tool in the development phases of MRI contrast agents, over the last decade FFC-NMR has gained interest in the characterisation of biological tissues and diseases [7][8][9][10] by either exploiting the endogenous 1 H R 1 NMRD profile itself, or its modifications produced by exogenous contrast agents.…”