The author acknowledges funding from the EPSRC through the Centre for Doctoral Training in Integrated Magnetic Resonance.Non peer reviewedPublisher PD

Broche, Lionel

Lurie, David John

Ross, P. James

English

The author acknowledges funding from the EPSRC through the Centre for Doctoral Training in Integrated Magnetic Resonance.Non peer reviewe

Aberdeen University Research

		8th	Conference	on	Field	Cycling	NMR	Relaxometry,	Turin,	Italy,	May	2013	 pP16		Figure 3: R1 dispersion curve for the RoI shownin Figure 2. The quadrupole peaks arising due toimmobile proteins in muscle are clearly visible(see arrows). Figure 1: Dispersion curves for a phantom ofcross-linked BSA obtained using the FC-FSEsequence (solid dots) show good agreement withresults from a commercial relaxometer (opencircles).    Rapid Field-Cycling MRI using Fast Spin-Echo P. James Ross, Lionel M. Broche, David J. Lurie Aberdeen Biomedical Imaging Centre, University of Aberdeen, AB25 2ZD, Scotland, UK www.ffc-mri.org  Introduction: Fast Field-Cycling MRI (FFC-MRI)1 is an emerging technique that aims to combine the capabilities of MRI and FFC-NMR by making it possible to rapidly vary B0 during an imaging sequence. Conventional relaxometric imaging is limited by lengthy scan times, since to estimate R1 at least two images (i.e. IR and SR) must be acquired at each field strength. In this work we describe an adaptation of the well known Fast Spin-Echo imaging sequence3 for FFC-MRI, named Field-Cycling Fast Spin Echo (FC-FSE) which enables relaxometric imaging in a fraction of the time that would otherwise be required. Methods: Imaging was carried out on a home-built whole-body field-cycling imager with a 59 mT detection field4. The system uses a commercial console (SMIS Ltd., U.K.). For each experiment a saturation recovery and inversion recovery image are acquired at the detection field. A single field-cycling inversion recovery image is then acquired for every evolution field of interest. R1 is estimated at each field using a two-point method. For validation of results relaxometry was also performed on small samples using a commercial bench-top field-cycling relaxometer (SMARtracer, Stelar s.r.l., Italy). Results: There is good agreement between the R1 dispersion results (Figure 1) obtained using the FC-FSE sequence and those obtained using the relaxometer for a phantom consisting of crosslinked bovine serum albumin (BSA). FC-FSE images from a volunteer’s thighs using an echo train length of 4 (Figure 2) exhibit virtually no artifacts from field-instability. A dispersion curve (Figure 3) obtained from the outlined region-of-interest in muscle shows pronounced quadrupole peaks, arising due to 1H-14N cross-relaxation in immobile protein molecules within the muscle. The total scan time was ~30 minutes compared to the 4 hours that would have been required using conventional relaxometric imaging.  Conclusions: This work has demonstrated that relaxometric imaging can be performed up to 8 times faster relative to the basic procedure, with virtually no sacrifice in the accuracy of R1 determination. This paves the way for clinical relaxometric studies with acceptable scan times.  Acknowledgements: The author acknowledges funding from the EPSRC through the Centre for Doctoral Training in Integrated Magnetic Resonance. References [1] Lurie, D.J. et al., C.R. Physique 11, 136-148, 2010.   [2] Pine, K.J. et al., Magn Reson Med, 63, 1698-1702, 2010. [3] Hennig, J. et al., Magn Reson Med, 3, 823-833, 1986. [4] Lurie, D.J. et al., Phys Med Biol, 43, 1877-1886, 1998. Figure 2: Image of a volunteer’s thighs obtainedusing the FC-FSE sequence with a speed upfactor of 4. RoI delineates muscle, from which adispersion curve was obtained. 

Rapid Field-Cycling MRI using Fast Spin-Echo

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Rapid Field-Cycling MRI using Fast Spin-Echo

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