(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.