Elasticity and viscoelasticity of embolization microspheres

The present study investigates the mechanical properties of three embolization microspheres (E-ms): tris-acryl gelatin microspheres (TG-ms), acrylamido polyvinyl alcohol microspheres (APVA-ms), and polyphosphazene-coated polymethylmethacrylate microspheres (PP-PMMA-ms). Compression and relaxation tests were performed on monolayers of particles and their Young's moduli and relaxation half times (RHTs) were determined. The elasticity of E-ms was evaluated by applying Hertz theory with the assumptions of incompressibility and a Poisson's ratio of 0.5. The Young's moduli of TG-ms, APVA-ms, and PP-PMMA-ms were 39.6 +/- 5.05 kPa, 18.8 +/- 4.00 kPa, and 13.6 +/- 1.98 kPa, respectively. The RHTs of TG-ms, APVA-ms, and PP-PMMA-ms were 52.3 +/- 5.56 s, 59.1 +/- 8.16 s, and 31.0 +/- 7.01 s, respectively. TG-ms have a high rigidity and deform slightly under a sustained compression since they have a high elasticity. PP-PMMA-ms are soft and deform a lot under sustained compression. They are more viscous than the other two microspheres. APVA-ms have intermediate material properties, having the same low rigidity as PP-PMMA-ms and being more elastic than TG-ms. (C) 2011 Elsevier Ltd. All rights reserved.