Temperature-Dependent Dielectric Properties of Lung

In recent years, microwaves (MW) have been used as an alternative modality for cancer therapy. The main area of application so far has been liver cancer. However, MW hyperthermia has also started to be used for the ablation of lung tumours. Published data on dielectric properties of lung tissue are limited but essential for reliable treatment planning and MW applicator design. The data presently available on lung tissue are scarce at body temperature and, to the authors' knowledge, no data exists on how dielectric properties vary with increasing temperature during the ablation process. Our study addresses this issue by investigating the dielectric properties of excised ovine lung tissue over a temperature range of 21 to 90 °C and over the frequency range 0.5 to 8.5 GHz. The tissue samples were heated by two distinct methods: a MW oven and a MW thermal ablator. Room temperature measurements reveal a significant spatial variability in tissue dielectric properties. The study also shows that as the temperature increases, both the real and imaginary parts of the permittivity decrease with frequency and increasing temperature.