Characterization of Microwave Generator Energy and Ablation Volumes Following Transarterial Embolization in an In Vivo Porcine Liver Model

Purpose This study aims to characterize the relationship between ablation zone volume (AZV) and microwave ablation (MWA) energy in an in vivo porcine liver model following arterial embolization. Materials and Methods With animal IRB approval, eleven female swine underwent either right (n= 5) or left (n= 6) hepatic artery embolization under fluoroscopic guidance. Subsequently, ultrasound guided MWA was performed in each liver segment (left lateral, left medial, right medial, right lateral) at either 30 Watts (W) (n=4 lobes), 60W (n=4), 65W (n=20), 90W (n=8), 120W (n=4), or 140W (n=4) continuously for 5 minutes. Post-procedural volumetric segmentation was performed on standardized multiphase T1 MRI sequences. Results AZVs in embolized lobes (15.8 ± 10.6 mL) were significantly larger than non-embolized lobes (11.2 ± 6.5 mL, P <0.01). MWA energy demonstrated significant positive linear correlation with both embolized (R2=0.66, P <0.01) and non-embolized lobes (R2=0.64, P < 0.01). The slope of the linear models corresponded to a 0.95 ± 0.16 and 0.54 ± 0.09 mL/kJ increase in ablation volume per applied kJ of energy (E) in embolized and non-embolized lobes, respectively. In the multivariate model, embolization status significantly modified the relationship between E and AZV as described by the interaction term: 0.42*E*(Embolization Status), (P = 0.031). Conclusion Linear models demonstrate a near 1.8 fold increase in ratio of AZV per unit E, R(AZV:E), when applied to embolized lobes relative to non-embolized lobes. Absolute AZV differences between embolized and non-embolized lobes were greater at higher power MWA.