A Dual-Slot Microwave Antenna for More Spherical Ablation Zones: Ex Vivo and in Vivo Validation

Abstract

Purpose:To compare the performance of a microwave antenna design with two annular slots to that of a monopole antenna design in creating a more spherical ablation zone. Materials and Methods:Animal care and use committee approval was obtained before in vivo experiments were performed. Microwave ablation zones were created by using dual-slot and monopole control antennas for 2, 5, and 10 minutes at 50 and 100 W in ex vivo bovine livers. Dual-slot and monopole antennas were then used to create ablation zones at 100 W for 5 minutes in in vivo porcine livers, which also underwent intraprocedural imaging. Ablation diameter, length, and aspect ratio (diameter 4 length) were measured at gross pathologic examination and compared at each combination of power and time by using the paired Student t test. A P value less than .05 was considered to indicate a significant difference. Aspect ratios closer to 1 reflected a more spherical ablation zone. Results:The dual-slot antenna created ablation zones with a higher aspect ratio at 50 W for 2 minutes (0.75 vs 0.53, P = .003) and 5 minutes (0.82 vs 0.63, P = .053) than did the monopole antenna in ex vivo liver tissue, although the difference was only significant at 2 minutes. At 100 W, the dual-slot antenna had a significantly higher aspect ratio at 2 minutes (0.52 vs 0.42, P = .002). In vivo studies showed significantly higher aspect ratios at 100 W for 5 minutes (0.63 vs 0.53, respectively, P = .029). Intraprocedural imaging confirmed this characterization, showing higher rates of ablation zone growth and heating primarily at the early stages of the ablation procedure when the dual-slot antenna was used. Conclusion:The dual-slot microwave antenna created a more spherical ablation zone than did the monopole antenna both in vivo and ex vivo liver tissue. Greater control over power delivery can potentially extend the advantages of the dualslot antenna design to higher power and longer treatment times.q RSNA, 2013 1

Modeling and Validation of Microwave Ablations With Internal Vaporization

“…The simulated rate of radial and longitudinal ablation zone growth was greatest at the beginning of the heating cycle, then decreased over time as noted in previous experimental studies [24]–[26]. …”

Numerical Study on the Effect of Liquid Injection in Hepatic Microwave Ablation

“…There are still many defects in the treatment of large hepatocellular carcinoma. It's difficult for MWA to kill the entire tumor disposable, but multiple overlapping ablation will lead to incomplete coverage [4][5][6]. Therefore, expanding the lesion size is the key to improve the curative effect of microwave treatment of large hepatic tumors.…”

“…Therefore, expanding the lesion size is the key to improve the curative effect of microwave treatment of large hepatic tumors. Many scholars researched to improve the antenna structure and a large number of experimental studies has proved that the changing antenna significantly expand the ablation zone size [5][6][7][8]. The other approach is to add liquid during microwave ablation in order to expand the lesion size.…”

Theoretical evaluation of the treatment effectiveness of a novel coaxial multi-slot antenna for conformal microwave ablation of tumors

“…Many reports have focused on the comparison of single and double slots antennas [8,17,19,[27][28][29][30]. However, an effective method to design MWA antennas according to specific hepatic tumors with temperature-dependent properties has not yet been reported.…”