Broche, Lionel M

Davies, Gareth R

Lurie, David J

Payne, Nicholas R

Ross, P James

Zampetoulas, Vasileios

Aberdeen University Research

AMPERE NMR School, Zakopane, Poland, June 2015 – p14 FAST FIELD-CYCLING MRI: A NEW IMAGING MODALITY  David J. Lurie, Lionel M. Broche, Gareth R. Davies, Nicholas R. Payne,  P. James Ross and Vasileios Zampetoulas  Aberdeen Biomedical Imaging Centre, University of Aberdeen, AB25 2ZD, Scotland, UK www.ffc-mri.org    The use of Fast Field-Cycling (FFC) in combination with magnetic resonance imaging (MRI) has been increasing in recent years [1].   One of the first uses of FFC-MRI was in conjunction with Proton-Electron Double-Resonance Imaging (PEDRI) to image the distribution of free radicals in biological samples. Irradiating the Electron Spin Resonance (ESR) of a free radical solute enhances the water NMR signal, through the Overhauser effect. Field-cycling allows the ESR irradiation to be applied at low field (hence relatively low frequency, and low non-resonant absorption), while NMR signal detection and imaging is carried out at higher field, to preserve SNR [2].   NMR relaxometry refers to the measurement of relaxation times (usually T1) as a function of magnetic field strength. It is usually accomplished using FFC, in which the magnetic field is switched rapidly between levels during the pulse sequence. In this way, a single instrument can be used to measure T1 over a wide range of magnetic field strengths. The aim of FFC-MRI is to obtain spatially-resolved T1-dispersion data, by collecting images at a range of evolution field strengths [1]. We have recently demonstrated methods for implementing relaxometry on localised regions defined on a pilot image [3]. We have also shown that FFC relaxometry can detect the formation of cross-linked fibrin protein from fibrinogen in vitro, in a model of the blood clotting process, via the measurement of 14N-1H cross-relaxation phenomena [4], and we have demonstrated that FFC-MRI can detect changes in human cartilage induced by osteoarthritis [5]. Recent work has focussed on speeding up the collection of FFC-MRI images by incorporating rapid MRI scanning methods and improved pulse sequences and algorithms [6,7].  In our lab we have built a range of FFC-MRI equipment, including two whole-body human sized scanners, operating at detection fields of 0.06 T [8] and 0.2 T. The 0.06 T scanner uses a double magnet, with field-cycling being accomplished by switching on and off a resistive magnet inside the bore of a permanent magnet; this has the benefit of inherently high field stability during the detection period. We have also demonstrated technology for localised field switching within a clinical MRI system [9]. Our newest whole-body human sized scanner (0.2 T) uses a single resistive magnet, giving increased flexibility at the expense of greater complexity and susceptibility to magnetic field fluctuations.  This presentation will cover the main techniques used in FFC-MRI and will summarise current and potential bio-medical applications of the methods. [1] Lurie D.J., Aime S., et al., Comptes Rendus Physique 11, 136-148 (2010). [2] Lurie D.J., Hutchison J.M.S.,  et al., J. Magn. Reson. 84, 431-437 (1989). [3] Pine K.J., Davies G.R. and Lurie D.J., Magn.Reson.Med. 63, 1698–1702 (2010). [4] Broche L.M., Ismail S.R., et al., Magn.Reson.Med. 67, 1453-1457 (2012). [5] Broche L.M., Ashcroft G.P and Lurie D.J., Magn.Reson.Med. 68, 358-362 (2012). [6] Ross, P.J., Broche, L.M., and Lurie, D.J., Magn. Reson. Med. 73, 1120-1124 (2015). [7] Broche, L.M., Ross, P.J., Pine, K.J. and Lurie, D.J., J. Magn. Reson., 238, 44-51 (2014). [8] Lurie D.J., Foster M.A., et al., Phys.Med.Biol. 43, 1877-1886 (1998). [9] Pine K.J., Goldie F. and Lurie D.J., Magn. Reson. Med. 72, 1492-1497 (2014).  These references are available at http://www.ffc-mri.org/publications brought to you by COREView metadata, citation and similar papers at core.ac.ukprovided by Aberdeen University Research Archive

Fast Field-Cycling MRI : A New Imaging Modality

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