Polyvinyl alcohol (PVA) particles have been used for embolization procedures for over 20 years without reports of adverse or allergic reactions. At Weill Cornell Medical Center, we have used Biosphere Medical Embosphere particles exclusively Since April 2003 with excellent results. The injected particles will flow until they encounter a precisely chosen sized artery, and they will wedge in place in that position. They do not dissolve or get absorbed and they cannot migrate to other parts of the body.