Recently, there has been FDA clearance of a new anti-reflux catheter, Surefire® Infusion System (SIS, Westminster, CO). The current design has an expandable tip which collapses during forward flow, and then dynamically seal off the vessel with reversal of flow, analogous to a valve. SIS, with its expandable tip microcatheter, has been demonstrated clinically to cause a slight decrease in intra-arterial pressure in the antegrade, or downstream, vascular compartment. Although this device was designed primarily to prevent retrograde reflux of embolic agents, the downstream blood pressure reduction may serve as a biomarker on quantifying embolization.