Dielectric properties of human normal, malignant and cirrhotic liver tissue:in vivoandex vivomeasurements from 0.5 to 20 GHz using a precision open-ended coaxial probe

Abstract

Hepatic malignancies have historically been treated with surgical resection. Due to the shortcomings of this technique, there is interest in other, less invasive, treatment modalities, such as microwave hepatic ablation. Crucial to the development of this technique is the accurate knowledge of the dielectric properties of human liver tissue at microwave frequencies. To this end, we characterized the dielectric properties of in vivo and ex vivo normal, malignant and cirrhotic human liver tissues from 0.5 to 20 GHz. Analysis of our data at 915 MHz and 2.45 GHz indicates that the dielectric properties of ex vivo malignant liver tissue are 19 to 30% higher than normal tissue. The differences in the dielectric properties of in vivo malignant and normal liver tissue are not statistically significant (with the exception of effective conductivity at 915 MHz, where malignant tissue properties are 16% higher than normal). Also, the dielectric properties of in vivo normal liver tissue at 915 MHz and 2.45 GHz are 16 to 43% higher than ex vivo. No statistically significant differences were found between the dielectric properties of in vivo and ex vivo malignant tissue (with the exception of effective conductivity at 915 MHz, where malignant tissue properties are 28% higher than normal). We report the one-pole Cole-Cole parameters for ex vivo normal, malignant and cirrhotic liver tissue in this frequency range. We observe that wideband dielectric properties of in vivo liver tissue are different from the wideband dielectric properties of ex vivo liver tissue, and that the in vivo data cannot be represented in terms of a Cole-Cole model. Further work is needed to uncover the mechanisms responsible for the observed wideband trends in the in vivo liver data.

Dual‐slot antennas for microwave tissue heating: Parametric design analysis and experimental validation

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] However, previous studies have considered a fixed antenna geometry based on a 10 mm short-circuited stub and 1 mm slot width. Little focus has been given to the balance between reflection coefficient and antenna heating pattern.…”

“…The relative permittivity of liver can vary by more than 620% depending on tissue pathology or temperatures in the ablation zone. 25,26 Such changes affect power delivery and spatial heating pattern; therefore, baseline permittivity was varied by 6 30% in simulations to evaluate the effect on antenna performance. The mean percent difference in reflection coefficient between all variations and changes in heating pattern were noted.…”

Expanding the Repertoire of Dielectric Fractional Models: A Comprehensive Development and Functional Applications to Predict Metabolic Alterations in Experimentally-Inaccessible Cells or Tissues

“…The study of such phenomena finds multiple applications in physiology, in diagnostics, and in therapy [20]. One example can be given in cancer diagnostics; in particular, these phenomena allow the comparison of cancer cells to normal cells in order to highlight the evolution of the disease [10,43,44]. This technique can obviously be applied to many other diseases, and it is linked to the knowledge of the complex dielectric function (introduced in paragraph 3).…”

Investigation of the effect of dehydration on tissue dielectric properties in ex vivo measurements

“…In addition to healthy biological tissue, the dielectric properties of a wide range of cancerous tissue has also been dielectrically characterized. For example, a number of studies, (Chaudhary et al 1984, Surowiec et al 1988, Joines et al 1994, O'Rourke et al 2007, Sugitani et al 2014 characterized the dielectric properties of cancerous tissues that are being used in the development of medical diagnostic and therapeutic applications.…”