On the dual contrast enhancement mechanism in frequency-selective inversion-recovery magnetic resonance angiography (IRON-MRA)

The susceptibility of blood changes after administration of a paramagnetic contrast agent that shortens T₁. Concomitantly, the resonance frequency of the blood vessels shifts in a geometry-dependent way. This frequency change may be exploited for incremental contrast generation by applying a frequency-selective saturation prepulse prior to the imaging sequence. The dual origin of vascular enhancement depending first on off-resonance and second on T₁ lowering was investigated in vitro, together with the geometry dependence of the signal at 3T. First results obtained in an in vivo rabbit model are presented.