Spherical polyvinyl alcohol microspheres

Chua GC, Wilsher M, Young MP, Manyonda I, Morgan R, Belli AM (2005) Comparison of particle penetration with non-spherical polyvinyl alcohol versus trisacryl gelatin microspheres in women undergoing premyomectomy uterine artery embolization. Clin Radiol 60 116-122... 

These microspheres are precisely calibrated, spherical, hydrophilic, microporous beads made of tris-acryl co-polymer coated with gelatin. They come in defined range of sizes, ranging from 40 to 1200 pm in diameter. Their smooth hydrophilic surface, deformability and minimal aggregation tendency have been shown to result in a lower rate of catheter occlusion and more distal penetration into the small vessels [32]. Their efficacy has been evaluated in several conditions, and vdien compared to the standard polyvinyl alcohol particles (PVA) particles, a deeper penetration and embolization of smaller and more peripheral vessels may be achieved. This distal embolization may limit the development of any collateral blood supply. Also, in a study where PVA particles and tris-acryl microspheres of similar size were compared, the level of vascular occlusion with calibrated tris-acryl microspheres precisely correlated with particle size whereas the level of vascular occlusion with PVA particles did not. Another study has demonstrated that in embolized tumors. 

A long track record of safety and efficacy of polyvinyl alcohol led to the design of spherical PVA. PVA (Contour SE Microspheres Boston Scientific/Medi-tech, Natick, MA) and PVA hydrogel (Bead Block, Terumo Medical Corp., Somerset, NJ) are currently available for transcatheter use. 

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