Determining the relative permittivity of deep embedded biological tissues

Human tissue characterization, deep into the body, has been of interest for decades. X-rays are used for locating tumors. However, such surgery-free identification methods fail to verify whether tumors are benign or malignant without surgical extraction and testing of sample tissue. Moreover, X-ray scans do not allow for continuous time monitoring because frequent exposure to ionizing radiation and contrast agents is harmful to the human body. Probe methods do provide accurate approximation of the dielectric constant ε_r but requires direct access to the specimen, making them suitable only for in-vitro applications. On the other hand, while common wearable health monitoring systems are advantageous for everyday use, they are mainly focused on simple functions such as temperature, and heart rate monitoring.