Comparative study of four different spherical embolic particles in an animal model: a morphologic and histologic evaluation.

PURPOSE: To perform a study in a porcine model comparing four different spherical embolic particles in terms of postembolization patency, deformation, and potential for recanalization, with a focus on a relatively new agent--HepaSphere.

MATERIALS AND METHODS: Partial embolization of both kidneys was performed in 18 pigs. Nine animals were sacrificed at 48 hours and nine at 4 weeks. In the same animal, the right kidney was embolized with HepaSphere particles ("dry" size, 50-100 microm; presumed final size, 200-300 microm), and the left kidney was alternatively embolized with EmboSphere (100-300 microm), Contour (150-350 microm), or Bead Block (150-350 microm) particles. The authors analyzed the size, deformation, and number of particles in each vessel, their morphologic characteristics, and recanalization.

RESULTS: Particle sizes and deformation (1,096 particles) were as follows: HepaSphere, 225.3 microm +/- 67 and 26% +/- 19.7, respectively; EmboSphere, 132.9 microm +/- 36 and 18.1% +/- 14.2; Bead Block, 108.1 microm +/- 38 and 16.5% +/- 13.9; and Contour, 240.8 microm +/- 135 and 55.5% +/- 33. HepaSphere and Bead Block particles were distally located, and EmboSphere and Contour particles were located more proximally. EmboSphere and Bead Block particles were round, HepaSphere particles were round and/or ovoid, and Contour particles had an amorphous aspect. EmboSphere particles had a higher tendency to aggregate. No recanalization was seen with HepaSphere particles, and variable recanalization was observed with the others.

CONCLUSIONS: Despite similar initial morphologic characteristics, the performance of the agents tested in this study differed in terms of final size, shape, deformation, and luminal recanalization. These differences have potential clinical relevance, and the knowledge of the differing embolic performance may be helpful in choosing agents for specific therapeutic purposes.