Dara Ó Hógáin et al – Use of contrast agents with fast field-cycling magnetic resonance imaging Physics in Medicine and Biology 56, 105-115 (2011) 1 Use of contrast agents with fast field-cycling magnetic resonance imaging Dara Ó Hógáin 1 , Gareth R Davies 1 , Simona Baroni 2 , Silvio Aime 2,3 and David J Lurie 1 1 Aberdeen Biomedical Imaging Centre, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK 2 Invento S.r.l., Via Nizza 52, I-10126, Torino, Italy 3 Department of Chemistry ‘IFM’, University of Torino, Italy E-mail: d.lurie@abdn.ac.uk Abstract Fast Field-Cycling (FFC) MRI allows switching of the magnetic field during an imaging scan. FFC-MRI takes advantage of the T 1 dispersion properties of contrast agents to improve contrast, thus enabling more sensitive detection of the agent. A new contrast agent designed specifically for use with FFC was imaged using both a homebuilt FFC- MRI system and a 3 T Philips clinical MRI scanner. T 1 dispersion curves were obtained using a commercial relaxometer which showed large changes in relaxation rate between fields. A model of magnetization behaviour was used to predict optimum evolution times for maximum T 1 contrast between samples at each field. Images were processed and analysed to create maps of R 1 values using a set of images at each field. The R 1 maps produced at two different fields were then subtracted from each other in order to create a map of ∆R 1 in which pixel values depend on the change in R 1 of the sample between the two fields. The dispersion properties of the agent resulted in higher contrast in a ∆R 1 image compared with a standard T 1 -weighted image. PACS 87.61.Qr Physics in Medicine and Biology Key Words: Fast Field-Cycling, Contrast Agents, Manganese liposomes, ∆R 1 imaging