The Influence of Preablation Embolization Particle Size on the Size of the Microwave Ablation Zone in a Porcine Orthotopic Renal Tumor Model

Purpose: To determine the effect of arterial embolization using different embolic agents and sizes on microwave ablation (MWA) zone size in a porcine renal tumor (RT) model.

Materials and methods: In a transgenic porcine kidney, 32 sites were inoculated, with 28 orthotopic RTs induced. Experimental groups (23 tumors) underwent angiography with arterial embolization using various embolic materials (calibrated particles from 40 to 1,200 μm, and ethiodized oil) to achieve vascular stasis of the RT. MWA using a standard protocol (3 minutes at 65 W) was subsequently performed for all tumors. Gross and histologic ex vivo analyses of the ablation zones were performed.

Results: Control group ablation zone volume without prior embolization was 5.24 cm³ (SD ± 0.55). Ablation zones after embolization with 40 μm, 100 μm, 300-500 μm, 900-1,200 μm particles were significantly larger than those with MWA alone (mean, 15.39 cm³ [SD ± 4.54]; P = .002; 11.07 cm³ [SD ± 1.39]; P = .001; 8.68 cm³ [SD ± 0.77]; P = .001; and 9.90 cm³ [SD ± 1.62]; P = .002, respectively). Liquid embolic ethiodized oil emulsion did not create a significant increase in the ablation zone (5.92 cm³ [SD ± 1.43 cm³]; P = .492).

Conclusions: Pre-MWA arterial embolization in a porcine RT model produced a statistically significant increase in the ablation zone when compared with MWA alone. Using smaller particle size embolic material with distal embolization at the tumor arterioles (50-150 μm) produced the largest, almost 3-fold increase in ablation zone volume.