In Vivo Measurements of Murine Melanoma's Complex Permittivity Between 500 MHz and 8.5 GHz

Complex permittivity measurements of murine melanoma tumors were performed via an open-ended coaxial probe technique for frequencies ranging from 500 MHz to 8.5 GHz. The measurements were conducted in five mice containing a melanoma tumor each while the animals were under anesthesia. Two different measurement methodologies were employed. Eighty-six in vivo measurements of melanoma's permittivity were collected with the open-ended coaxial probe placed directly on the tumors. A one-pole Cole–Cole model was fitted to the melanoma's median curve. The data were organized in a nested structure; hence, generalized linear mixed-effects models were employed over the entire frequency band to evaluate between-tumor and between-location variabilities. Results revealed a larger between-location variability, indicating intra-tumoral heterogeneity, which was visually confirmed. Additionally, generalized linear mixed-effect models were also employed to assess the measurement methodologies for 500 MHz, 4.5 GHz, and 8.5 GHz.