Figure 1

Frequency distribution surrounding a cylindrical tube containing a suspension of iron oxide nanoparticles. (a). Positive contrast MRI is thus enabled by the specific saturation of on-resonant spins (b). In human volunteers, a cylindrical iron oxide loaded container was placed adjacent to the upper leg causing a frequency dispersion in the tissue (c). By applying a 3D GRE MRI acquisition preceded by a narrow band saturation RF pulse with a specific delay time, flowing spins are effectively tagged (d). This tag progresses as delay times are increased from 0 ms (e) to 0.8 s (h), visualizing flow along the femoral vein (yellow arrow) and artery (green arrow). Time of flight (TOF) MRA displaying the femoral vein and artery (i). A specific off resonance frequency band (red arrow, 1e) is clearly affected by the fat saturation pulse. To enhance the moving contrast front,the images with a delay time of 0 s were subtracte from those with a delay time of 0.2 s (j), 0.4 s (k) and 0.8 s (l).