(A) Selected examples of a few Gd-based clinically used MRI contrast agents (Magnevist, Gadovist and Primovist) and Gd-Pt heterometallic MRI-based theranostics. (B) In vivo T₁-weighted MR images of B6 mice at 8 and 60 min after the injection of 29a, 29b and Gd–DTPA at a dose of 0.1 mmol Gd / kg of body weight and the corresponding signal-decay curves. The circles indicate the area of the kidneys. Reprinted with permission from reference [129]. Copyright 2014, Wiley. (C) XRF elemental distribution maps for Gd, and Pt of a single A549 human lung carcinoma cell. Cells were treated with 5 µM of 28b for 24 h. Maximal area densities are given in µgcm⁻² for each element at the bottom of each map. Reprinted with permission from reference [128]. Copyright 2010, Wiley.