**Acknowledgements**

This review is written in the context of a study that was funded by EU FP7 DoReMi (grant agreement 249689) on "low dose research towards multidisciplinary integration,", by EU FP7 ProCardio project (grant agreement 295823) and by the Federal Agency of Nuclear Control (FANC-AFCN, Belgium) (grant agreement: CO-90-13-3289-00). R. Ramadam and B. Baselet are recipients of a doctoral SCK•CEN/Ghent University grant and of a doctoral SCK•CEN/ Université catholique de Louvain grant, respectively. P. Sonveaux is a Senior Research Associate of the Belgian National Fonds de la Recherche Scientifique.
