# Phase Compensation Technique for Effective Heat Focusing in Microwave Hyperthermia Systems
## 5 Conclusions  
An antenna array that uses the phase compensation technique to effectively concentrate EM energy during microwave hyperthermia treatment for deep-seated breast cancer was proposed in this paper. The thermal effect was determined based on the E-field absorbed in the therapeutic region. To deliver EM energy inside the human breast, the input phases of each antenna should be controlled based on the location of the tumor cells. Strong constructive interference in the target area can be achieved when each TSA has equal polarization characteristics. Therefore, the direction of each antenna and array configuration was optimized for effective E-field synthesis. Moreover, accurate phase control is needed on the target area to minimize thermal damage to normal cells. The input phase of each antenna in the 12-element array was calculated for single and multiple targets depending on the tumor condition in the breast phantom. For multiple targets in particular, sub-array beam focusing was applied to simultaneously provide therapeutic effects on the multifocal breast cancer. To minimize interference between the sub-arrays, the values of the modified phase for phase compensation were added to the antennas in one of the sub-arrays so that sub-arrays #1 and #2 were out-of-phase. The temperature distribution of the single tumor and multiple tumor cases were simulated and measured to verify the therapeutic performance of the proposed approach. Consequently, the proposed 12-element array system and the phase compensation technique provided enhanced therapeutic capabilities for breast cancer hyperthermia treatment.  
Figure 13: The transient temperature distribution at the tumor center: (**a**) single tumor at (0,0) mm, (**b**) single tumor at (20,0) mm, and (**c**) two tumors at (15,10) mm and (\(-\)15,\(-\)10) mm.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **Single Tumor at (0,0) mm** & **Single Tumor at (20,0) mm** &
\begin{tabular}{c} **Two Tumors at (15,10) mm, (-15,\(-\)10) mm** \\ **(-15,\(-\)10) mm** \\ \end{tabular} \\ \hline Input RF power (W) & 7.1 & 6 & 7.1 \\ Maximum SAR in the simulation (W/kg) & 18.1 & 23.1 & 14.1 \\ Maximum temperature increase & 8.4 & 8.5 & 7.8 \\ in simulation (\({}^{\circ}\)C) & 8.3 & 8.3 & 7.7 \\ Maximum temperature increase & 8.3 & 8.3 & 7.7 \\ in measurement (\({}^{\circ}\)C) & 226.9 & 201 & 153.9 \\ ETA in measurement (mm\({}^{2}\)) & 216.3 & 195.9 & 132.7 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of the simulation and measurement results.  
**Author Contributions:** Data curation and writing--original draft preparation, S.L.; writing--review and editing, S.L. and Y.J.Y.; supervision, Y.J.Y. Both authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy restrictions.  
**Acknowledgments:** This paper was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. NRF-2019R1A2C1005764).  
**Conflicts of Interest:** The authors declare no conflict of interest.