In Vivo and Ex Vivo Dielectric Characterization of Human Tissues in the Abdominal Area at the Microwave Band

The dielectric characterization of biological tissues is essential for different medical applications. Due to ethical constraints, comprehensive characterization of human tissues remains a significant challenge. There is a large database of measurements on animals, but limited research has been conducted in humans, especially at the abdominal area at in vivo conditions. This study presents an in-depth analysis of the dielectric properties of human abdominal tissues such as liver, small intestine, and fat, both in vivo and ex vivo. Measurements were conducted both in vivo and ex vivo, using the open-ended coaxial probe method within 0.5 - 26.5 GHz band. Both fat and small intestine tissues were measured at ex vivo and in vivo conditions, while liver was measured only under in vivo conditions. The obtained dielectric properties were analyzed for each tissue and scenario. Results are compared to other reported studies and 2-pole Cole-Cole model parameters are reported to allow reproducibility of the tissue behavior. These findings contribute to expanding the existing database on dielectric properties of human tissues, particularly for abdominal tissues in humans in vivo, of which there are few measurements in the literature.