Fig. 2.

Plot of [Ni²⁺] relaxivities in 2% agarose against field strength. Closed circles: this work, 19.36 ± 1.20 °C. Open circle: data from initial 1 5 T characterization of the phantom materials (see supplementary material), 21.5 °C. Standard error of fit is shown, although for B₀ between 1 5 T and 7 T the standard errors of between 0.19% and 0.48% are not evident as they are smaller than the size of the symbol. Other symbols: estimated from literature. +, parameter c₁ in [3], 22 °C. −, estimated, with standard error, from Fig. 1 in [9], 22 °C. ×, estimated, with standard error, from Fig. 4 in [15], 20 °C. ◇, ◻︎, estimated from Fig. 2 in [16], 19 °C and 22 °C respectively.