Preparation of DEBs. The embolization beads used in this study were composed of a sulfonate-modified poly(vinyl alcohol) hydrogel that has the capability of interacting with therapeutic agents (16). More specifically, these beads were prepared by the reverse suspension polymerization of a methacyloyl-modified polyvinyl alcohol macromer, synthesized by the reaction of polyvinyl alcohol with N-acrylamidoaminoacetaldehyde followed by copolymerization with 2-acrylamido-2-methylpropane sulfonate by free radical polymerization.