Fast gradient echo sequences are used to study dynamic processes with time periods on the order of a second and allow continuous monitoring of most physiologic motions. A common use of dynamic scanning is the investigation of the time course of tissue contrast after injection of a paramagnetic contrast agent.

(Dy) The Dysprosium chelates are analogs of the extracellular gadolinium chelates, with substitution of the dysprosium ion for the gadolinium ion and offers advantages in application on first pass studies. The use of a dysprosium-based contrast agent (Dy-type) instead of a gadolinium-type (Gd-type) is an alternative in cases of a disrupted blood brain barrier. Because of its much smaller T1 enhancement, this contrast agent should give more accurate perfusion calculations in brain MRI.