Potential clinical applications of terahertz radiation

Terahertz radiation has significant potential in medical diagnosis and treatment because its frequency range corresponds to the characteristic energy of biomolecular motion. Advantageously, terahertz-specific low energy does not cause the ionization of biomolecules. In this paper, we review several state-of-the-art terahertz biomedical techniques and results and suggest potential techniques that may be applicable in real-world clinics in the near future. First, some techniques for enhancing the penetration depth into wet biological tissues are surveyed. Endoscopy and otoscopy methods for approaching internal organs are then discussed. The operation principles of sensors utilizing terahertz radiation are explained, and certain sensing examples related to blood disorders, diabetes, and breathing conditions are presented. The greatest potential of terahertz radiation in biomedical applications so far has been in cancer imaging, because terahertz radiation is ideal for measuring the superficial soft tissues in which most cancers occur. The examples presented herein include skin, oral, gastric, breast, and brain cancers. In search of a cancer-specific signal using terahertz radiation, methylated malignant DNA has been found to exhibit a characteristic resonance at approximately 1.65 THz. This resonance may help treat cancer through the demethylation of malignant DNA using high-power terahertz irradiation at this specific frequency, as well as serving as a potential cancer biomarker.