Multimodal “imageable” embolic microspheres: A preliminary study on occlusion effectiveness, level of occlusion, and arterial distribution in a swine liver model

To assess multi-modal visibility (radiography and cone-beam computed tomography (CBCT)), occlusion effectiveness, level of occlusion, and arterial distribution for imageable embolic microspheres (IEMs) in a swine liver model. 90-250µm IEMs (Lot. L13010401) were synthesized from a multicomponent glass [1]. 4 pigs (30-33Kg) received left or right hepatic artery embolization (LHAE, n = 3/RHAE, n = 1) with between 0.35-0.75cc IEMs (no contrast), until complete occlusion of target areas was detected angiographically. A qualitative evaluation of IEM visibility via X-ray fluoroscopy and CBCT was graded per the following scoring scheme: 1 = no visibility, 2 = faint, 3 = fair, 4 = good and 5 = excellent. Occlusion effectiveness was assessed via DSA for each hepatic segment and division branch with IEMs per the following scheme: 1 = regular flow, 2 = reduced flow (<50%), 3 = sluggish flow and 4 = no flow. For level of occlusion, hepatic segments (I to VIII) and branches reached by IEMs were qualitatively assessed using X-ray fluoroscopy and CBCT, with an assessment of arterial distribution between sequential injections (0.05-0.3mL). Good to excellent visualization was shown under X-ray fluoroscopy and CBCT with initial injection of 0.15-0.4cc IEMs. Subsequent injections did not significantly alter visualization characteristics until ≥0.25cc. Complete occlusion effectiveness was noted in all hepatic segments and division branches reached by IEMs in 3/4 treatments. A <50% reduction in flow was achieved for segments reached in the remaining treatment, with reduced or regular flow in segment II to IV division branches. IEMs were shown to reach up to 4th division branches in segments V and VIII for RHAE versus 1st to 3rd/4th division branches in segments II to IV for LHAE (with exception of one animal where segments V and VIII were reached). For all treatments, IEMs successfully filled target arteries on initial injection, with subsequent injections of IEMs accumulating thereafter, distal to proximal. IEMs evaluated herein permit real-time intraprocedural visualization, without contrast, for precise control of level of occlusion and arterial distribution to standardize transarterial embolization.