**5. Conclusion**

In conclusion, this chapter presented an exhaustive summary of MI approaches with particular focus on implementations of microwave breast imaging theory, including image algorithms, experimental setups, microwave sensors and sensor arrays. Several MI implementation apparatuses were reviewed in detail. MI systems have direct impacts on spatial resolution, operating frequencies, detection accuracy and quality of imaging. Several advantages of existing MI approaches, open challenges, possible solutions and future research directions were also discussed. Successful clinical trials of MI for breast imaging made the worldwide excitation, and this achievement confirmed that MI has potential to become a low-risk alternative to existing medical imaging tools such as X-ray mammography for breast cancer detection. However, MI-based techniques are still far from maturity due to the fact that many challenges have to be addressed before MI can be implemented in clinical environments.
