Evaluation of tris-acryl gelatin microsphere embolization with monochromatic x rays: Comparison with polyvinyl alcohol particles

PURPOSE: Imaging of blood vessels 30 gm or smaller can be achieved with use of monochromatic x rays. The purpose of the present investigation was to use this method to evaluate the in vivo primary embolic effect of tris-acryl gelatin microspheres and polyvinyl alcohol (PVA) particles in small blood vessels, and specifically to assess the distribution of these particles and the resulting changes in circulation. MATERIALS AND METHODS: Twelve rabbits were divided into four groups: group 1 (PVA particles, 90-180 mu m; n = 3), group 2 (tris-acryl gelatin microspheres, 40-120 mu m; n = 3), group 3 (PVA, 300-500 mu m; n = 3), and group 4 (tris-acryl gelatin microspheres, 300-500 mu m; n = 3). After microangiography with monochromatic x rays, embolization was performed in normal auricular blood vessels, and immediately thereafter, postembolization microangiography was performed. Images acquired before and after embolization with the four embolic agents were compared, and the diameters of embolized blood vessels were measured. The mean embolized vascular diameter and its ratio to the midrange particle size of the embolic agent were calculated. RESULTS: Tris-acryl gelatin microspheres did not aggregate and tended to lodge in vessels close in size to the individual particle size, whereas PVA particles aggregated in vessels larger than the individual particle size. For tris-acryl gelatin microspheres, no blood flow was noted peripheral to the embolized region, whereas for PVA particles, blood flow was noted in regions peripheral to the embolized region. CONCLUSIONS: Monochromatic x rays allow direct visualization of in vivo embolic properties. This technique holds promise for comparative studies of embolic agents.