Radio wave/microwave-involved methods for cancer diagnosis

Microwave radiations are a section of the electromagnetic spectrum that ranges in frequency from 300MHz to 300GHz. The most common microwave applications are in households, communications, the military, industry, and medicine. In recent years, the microwave has been successfully used within medicine to treat and diagnose diseases such as cancer. Moreover, the microwave imaging (MWI) technique is cost-effective and uses nonionizing radiation for its application in medical diagnostics. MWI can be obtained directly from different dielectric characteristics of malignant tissue compared with those of normal tissue or indirectly revealed by hybrid techniques. This chapter will introduce some relevant knowledge about microwave radiation, dielectric, and polarization. Then, general aspects of AC relaxation, dispersion, and the mathematical model of dispersion are explained. In the next section, we will differentiate permittivity in healthy tissue from malignant tumor tissue, as well as the recent research on the application of nanomaterials as microwave contrast agents. In the next part of this chapter, we focus on the application of radio waves in diagnosis by introducing magnetic resonance imaging (MRI) principles, the mechanism of MRI image contrast, and finally, MRI contrast agents including paramagnetic and superparamagnetic nanoparticles.