Phantom CEST images of the Eu3+ complexes Eu-1 (20 mm), Eu-2 (15 mm), and Eu-3 (11 mm) recorded at 4.7 T, 298 K in water at pH 7 using a B1 of 9 μT. a) Representation of the phantom containing six wells: water (W), Eu-1, Eu-2, Eu-3, and a mixture of the three complexes (M). b) PARACEST difference images of the complexes Eu-1, Eu-2, and Eu-3. c) Quantitative CEST contrast for each Eu3+ complex in the presence of other agents, Eu-1 (cylinder), Eu-2 (pyramid), and Eu-3 (rectangle). Shown are the frequencies freqselect at which the EuIII complexes are selective.