Magnetic resonance angiography has made great strides, with continuing improvements in hardware, pulse sequencing, and know-how allowing ever-increasing speed, resolution, and suppression of artifacts. However, an inherent physical barrier has always been limited SNR. Gadolinium contrast agents help to increase SNR by facilitating T1 relaxation, but they can be injected only at a finite rate and at a limited molar dose, and there is a rapid drop in c- centration following the brief arterial phase due to redistribution into the extracellular fluid compartment. With its sixfold increase in T1...