Elastic characteristics of microspherical embolic agents used for vascular interventional radiology

Embolic agents are used in vascular interventional radiology to occlude arteries under pathological conditions. The present study was performed to investigate the material properties of two microspherical embolic agents (MSEAs), tris-acryl gelatin microspheres (TGMS) and superabsorbent polymer microsphere (SAP-MS), using a loading-unloading compression test. The results demonstrated that for both TGMS and SAP-MS, the stress-strain relationship appeared to be linear up to 25% deformation. Therefore, one can reasonably treat TGMS and SAP-MS as linearly elastic materials for this range of deformation and apply the Hertz contact theory for analysis of the Young's modulus. The Young's moduli of TGMS and the SAP-MS obtained by applying Hertz theory under the assumption of a Poisson's ratio of 0.5 were 19.33 +/- 4.97 kPa and 9.64 +/- 2.46 kPa, respectively (mean +/- SD, P<0.001, Mann-Whitney U-test), indicating that TGMS showed higher stiffness than SAP-MS. The effects of a difference in these mechanical characteristics of embolic agents on the performance of interventional radiology were discussed from a viewpoint of their flowing behavior and clinical aspects.