The rapidly growing field of molecular imaging seeking for real-time monitoring of molecular events occurring at the cellular level pushes MRI to higher magnetic fields. MRI molecular imaging can only be performed using targeted and responsive probes translating the molecular information to signal contrast in the image. A major goal in the development of such probes, besides targeting and response, is optimization of efficiency which is in general expressed as relaxivity. The parameters influencing relaxivity of gadolinium based T1 contrast agents are known and new agents could be designed using a guided strategy.Relaxivity induced by gadolinium ions is however strongly dependent on the magnetic field applied in MRI. Unfortunately the efficiency of Gd-based chelates decreases strongly at magnetic fields higher than 3 T (see Figure). New strategies different from those used at conventional MRI fields have to be applied. Figure: Inner-sphere relaxivity calculated for increaing rotational correlation times as a function of the magnetic fieldIn this contribution I will review strategies to get high T1 relaxation enhancement at high magnetic fields. I will show in which respect strategies differ from optimization for low field contrast agents and what the pitfalls are to be avoided.

High relaxivity MRI contrast agents for high magnetic field � challenges and pitfalls

247th National Meeting (2014)

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