During the last decade, different approaches were designed to detect USPIO. Positive contrast imaging based on a single off resonance RF excitation suffers of low sensitivity and miss registrated spatial localization. A way to avoid these drawbacks is the ORS sequence, based on a long RF saturation to affect off resonance water diffusible protons. The purpose of this study was to investigate a new sequence initially performed for CEST imaging, WASSR, to combined strong contrast, high sensitivity and quantification. This sequence was evaluated on Iron and Gadolinium based contrast agents in in vitro conditions at clinical and research fields.