Fast field-cycling magnetic resonance imaging

Abstract

Fast-field cycling magnetic resonance imaging FFC-MRI Earth-field MRI Pre-polarised MRI Free-radical imaging Magnetisation-transfer contrast Mots-clés : IRM en champ cyclé FFC-IRM IRM en champ magnétique terrestre IRM prépolarisée Imagerie par radicaux libres Contraste par transfert de magnetisationMagnetic resonance imaging (MRI) and fast field-cycling (FFC) NMR are both welldeveloped methods. The combination of these techniques, namely fast field-cycling magnetic resonance imaging (FFC-MRI) is much less well-known. Nevertheless, FFC-MRI has a number of significant applications and advantages over conventional techniques, and is being pursued in a number of laboratories. This article reviews the progress in FFC-MRI over the last two decades, particularly in the areas of Earth's field and prepolarised MRI, as well as free radical imaging using field-cycling Overhauser MRI. Different approaches to magnet design for FFC-MRI are also described. The paper then goes on to discuss recent techniques and applications of FFC-MRI, including protein measurement via quadrupolar cross-relaxation, contrast agent studies, localised relaxometry and FFC-MRI with magnetisation-transfer contrast. r é s u m é L'imagerie par Résonance Magnétique (IRM, ou MRI en anglais) et la RMN avec cyclage de champ rapide (« fast field cycling », FFC) sont toutes deux des méthodes bien développées. La combinaison de ces techniques, c'est-à-dire l'imagerie par résonance magnétique avec cyclage de champ rapide (FFC-MRI en anglais) est beaucoup moins bien connue. Cependant, la FFC-MRI a un nombre d'applications et d'avantages significatifs par rapport aux techniques conventionnelles, et son étude est poursuivie dans un certain nombre de laboratoires. Cet article passe en revue les progrès de la FFC-MRI au cours des deux dernières décennies, en particulier dans les domaines de l'imagerie en champ terrestre avec pré-polarisation, de même que l'imagerie des radicaux libres en utilisant la FFC-MRI avec effet Overhauser. Diverses approches à la conception des aimants pour FFC-MRI sont également décrites. L'article continue en discutant des techniques et applications récentes de la FFC-MRI, telles que la mesure des protéines par relaxation croisée quadrupolaire, les études d'agents de contraste, la relaxométrie localisée et la FFC-MRI avec contraste par transfert d'aimantation.

Quantification and localization of contrast agents using delta relaxation enhanced magnetic resonance at 1.5 T

“…This combination of MRI and fast field-cycling (FFC) has experienced little attention so far, but is promising for many new R 1 specific applications [4,6,9]. The offset coil is placed at the isocenter of a scanner and superposes its field parallel or antiparallel to the B 0 field.…”

Longitudinal gradient-coil with improved uniformity within the volume of interest

“…This essential feature is a consequence of enhanced differences between the relaxation times associated to the diverse components of the sample [6]- [8]. Relaxationweighted images obtained by this technique are otherwise impossible [9]- [10].…”

Comparative study of helical-cut notch–coil magnets for fast-field-cycling nuclear magnetic resonance

“…If needed, a prepolarization step can be added before the evolution part of the experiment to set up a nuclear magnetization [1,3]. Apart from relaxometry, FFC has also been successfully used for the indirect detection of quadrupolar resonances [6] and fieldcycling magnetic resonance imaging [7]. A major challenge today concerns the evolution of the associated hardware.…”

“…Fast-field-cycling nuclear magnetic resonance (FFC-NMR) has become a useful technique for scientific research [1][2][3][4][5][6][7]. It enables diverse experiments at low magnetic fields to be carried out when conventional NMR methods present severe limitations due to degradation of the signal-to-noise ratio of the free induction decay (NMR signal).…”