# Comparative Study of Minimally Invasive Microwave Ablation Applicators
## 4 Discussion  
Our objective was to replicate all designs proposed in the literature, with implementations closely following those reported in previous studies, using the data provided in  
Figure 9: Temperature distribution for applicators of Table 4 and deposited power levels: (**a**) monopole antenna with 25 W deposited power, (**b**) monopole antenna with tumor and 20 W deposited power, (**c**) capacitive-capped monopole antenna with 20 W deposited power, (**d**) capacitive-capped monopole antenna with tumor and 30 W deposited power, (**e**) balun-free base-fed monopole antenna with 30 W deposited power, (**f**) balun-free base-fed monopole antenna with tumor and 30 W deposited power, (**g**) dual-slot antenna with 25 W deposited power, (**h**) balun-free helical dipole antenna with 30 deposited power, (**i**) helical open waveguide structure with 10 W deposited power, and (**j**) helical open waveguide structure with tumor 15 W deposited power. Temperature contours are indicated by colors: blue (38 \({}^{\circ}\)C), purple (42 \({}^{\circ}\)C), red (46 \({}^{\circ}\)C), and yellow (50 \({}^{\circ}\)C). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Design**} & \multicolumn{6}{c}{**38 \({}^{\circ}\)C Penetration Zone**} \\ \cline{2-7}  & \multicolumn{2}{c}{**Diameter/d\({}_{1}\) (mm)**} & \multicolumn{2}{c}{**Length/d\({}_{2}\) (mm)**} & \multicolumn{2}{c}{**Extension Beyond the 3 mm or 2 mm Diameter**} & \multirow{2}{*}{**Figure**, **References**} \\ \cline{2-7}  & \multicolumn{1}{c}{**HM**} & \multicolumn{1}{c}{**TCM**} & \multicolumn{1}{c}{**HM**} & \multicolumn{1}{c}{**TCM**} & \multicolumn{1}{c}{**Diameter/d\({}_{1\text{TCM}}\)-d\({}_{\text{tumor}}\) =**} & \multicolumn{1}{c}{**Length/d\({}_{2\text{TCM}}\)-d\({}_{\text{tumor}}\) =**} & \multicolumn{1}{c}{**References**} \\ \cline{2-7}  & \multicolumn{1}{c}{**HM**} & \multicolumn{1}{c}{**TCM**} & \multicolumn{1}{c}{**HM**} & \multicolumn{1}{c}{**TCM**} & \multicolumn{1}{c}{**Extension Ring (mm)**} & \multicolumn{1}{c}{**Extension Ring g (mm)**} & \\ \hline Monopole & 48.4 & 45.4 & 80.8 & 85 & 25.4 & 65 & Figure 1a, [43] \\ \hline Capacitive capped monopole & 58.2 & 66.4 & 40 & 39.4 & 44.4 & 19.4 & Figure 1b, [44] \\ \hline Multi-slot & 51.9 & 56.4 & 53 & 54.1 & 26.4 & 24.1 & Figure 1c, [21] \\ \hline Dual-slot & 46.3 & 47.1 & 49.2 & 55.3 & 27.1 & 35.3 & Figure 1d, [45] \\ \hline Triaxial & 54 & 55.1 & 70.8 & 69.8 & 25.1 & 39.8 & Figure 1e, [47] \\ \hline Choke dipole & 55.1 & 56.6 & 65.2 & 63.5 & 26.6 & 33.5 & Figure 1f, [47] \\ \hline Balun-free base-fed monopole & 56.2 & 56.1 & 43.8 & 50.4 & 26.1 & 20.4 & Figure 1g, [47] \\ \hline PSD & 51.7 & 55.9 & 63.5 & 68 & 25.9 & 38 & Figure 1h, [46] \\ \hline Balun-free helical dipole & 53.3 & 55.1 & 63.1 & 63.7 & 25.1 & 33.7 & Figure 1i, [48] \\ \hline Helical open waveguide & 30.8 & 29.9 & 25.1 & 24.2 & 9.9 & 4.2 & Figure 1j, [41] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of all designs with respect to the 38 \({}^{\circ}\)C penetration zone. The two rightmost columns denote the depth g (mm) that the 38 \({}^{\circ}\)C isothermal extends beyond the tumor boundary. the respective publications. Figures 2-4 (results for the homogeneous model) show favorable comparisons with simulation and experimental results reported in the literature for the homogeneous model. However, when a tumor model volume of 2 cm or 3 cm, with distinct dielectric properties from healthy tissue (two-compartment model), is introduced (Figures 7 and 8), the shape and form of the temperature distribution are significantly altered and deformed. Similar observations are evident from the SAR distribution, shown in Figures 3 and 7. As demonstrated in Figures 2-8 and Table 3, some applicators produce nearly spherical ablation zones, indicating a uniform distribution of electromagnetic energy into the region of interest.