Histology-Validated Dielectric Characterisation of Lung Carcinoma Tissue for Microwave Thermal Ablation Applications

Microwave thermal ablation is a promising emerging treatment for early-stage lung cancer. Applicator design optimisation and treatment planning rely on accurate knowledge of dielectric tissue properties. Limited dielectric data are available in the literature for human lung tissue and pulmonary tumours. In this work, neoplastic and non-neoplastic lung dielectric properties are characterised and correlated with gross and histological morphology. Fifty-six surgical specimens were obtained from twelve patients undergoing lung resection for lung cancer in University Hospital of Galway, Ireland. Dielectric spectroscopy in the microwave frequency range (500 MHz-8.5 GHz) was performed on the ex vivo lung specimens with the open-ended coaxial probe technique (in the Department of Pathology). Dielectric data were analysed and correlated with the tissue histology. The dielectric properties of twelve lung tumours (67% non-small cell carcinoma (NSCC)) and uninvolved lung parenchyma were obtained. The values obtained from the neoplastic lung specimens (relative permittivity: 52.0 ± 5.4, effective conductivity: 1.9 ± 0.2 S/m, at 2.45 GHz) were on average twice the value of the non-neoplastic lung specimens (relative permittivity: 28.3 ± 6.7, effective conductivity: 1.0 ± 0.3 S/m, at 2.45 GHz). Dense fibrosis was comparable with tumour tissue (relative permittivity 49.3 ± 4.6, effective conductivity: 1.8 ± 0.1 S/m, at 2.45 GHz).