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JC Waterton, CDG Hines, PD Hockings, I Laitinen, S Ziemian, S Campbell, M Gottschalk, C Green, M Haase, K Hoffmann, H-P Juretschke, S Koehler, W Lloyd, Y Luo, I Mahmutovic Persson, JPB O Connor, LE Olsson, GJM Parker, K Pindoriah, JE Schneider, D Steinmann, K Strobel, I Teh, A Veltien, X Zhang, G Schuetz

British Chapter ISMRM Annual Meeting 24th-26th September 2018, Oxford, UK Poster Abstract PO-19

Background:  Many translational MR biomarkers derive from measurements of the longitudinal relaxation rate R₁, but evidence for between-site reproducibility of R₁ in small-animal MRI is lacking.  Objective: To assess R₁ repeatability and multi-site reproducibility in phantoms for preclinical MRI. Methods: R₁ was measured by saturation recovery in 2% agarose phantoms with five nickel chloride concentrations in 12 magnets at 5 field strengths in 11 centres on two different occasions within 1-13 days.  R₁ was analysed in three different regions of interest, giving 360 measurements in total.  Root-mean-square repeatability and reproducibility coefficients of variation were calculated.  Relaxivities were calculated.  Results: Day-to-day repeatability (N=180 regions of interest) was 2.3%.  Between-centre reproducibility (N=9 centres) was 1.4%.  The relaxivity of aqueous Ni²⁺ in 2% agarose varied between 0.66 s^-1mM^-1 at 3T and 0.94 s^-1mM^-1 at 11.7T.