Microwave techniques for biomedical applications aimed at cancer treatment or diagnosis, either by imaging or spectroscopy, are promising. Their use relies on knowledge of the dielectric properties of tissues, especially on a detectable difference between malignant and normal tissues. As most studies investigated the dielectric properties of ex vivo tissues, there is a need for better biophysical understanding of human tissues in their living state. As an essential component of tissues, cells represent valuable objects of analysis. The approach developed in this study is an investigation at cell level. Its aim was to compare human lung normal and malignant cells by dielectric spectroscopy in the beginning of the microwave range, where such information is of substantial biomedical importance. These cells were embedded in small and low-conductivity agarose hydrogels and laid on an open-ended coaxial probe connected to a vector network analyser operated from 200 MHz to 2 GHz. The comparison between normal and malignant cells was drawn using the variation of measured dielectric properties and fitting the measurements using the Maxwell-Wagner equation. Both methods revealed slight differences between the two cell lines, which were statistically significant regarding conductivities of composite gels and cells.
The reason for using acupuncture points as exposure sites in some applications of millimeter wave therapy has been unclear. Acupuncture points have been suspected to exhibit particular direct current (DC), low-frequency electrical and optical properties compared to surrounding skin. To assess if such a biophysical correlation could exist at millimeter wave frequencies used in the therapy, we investigated the dielectric properties of an acupuncture point on the forearm skin within the 50 -75 GHz range. These properties were compared with those of a neighboring ipsilateral control area and a corresponding contralateral control area. The complex reflection coefficient at the end of an open-ended rectangular waveguide loaded with a Teflon plug was measured with a vector network analyzer. A suitable model of the aperture admittance was used to calculate the dielectric properties of the skin at the measured spots. Statistical analyses were conducted with an ANOVA to compare the three sites. From these analyses, the dielectric properties of the acupuncture site were found to be somewhat different from those of surrounding non-acupuncture sites from 50 to about 61 GHz, in the case of the real part of the complex permittivity.
Abstract-Microwave Tomography (MWT) has recently attracted a significant interest for its potential biomedical applications. It has been shown that MWT might be applicable for non-invasive assessment of functional and pathological conditions of various soft tissues, including tissue malignancies. Since within this imaging modality tissues are differentiated and, consequentially can be imaged based on the contrast in dielectric properties, the diagnostic potentials of MWT are based on the contrast in dielectric properties between normal and malignant tissue. However, giving complexity of MWT imaging, especially for such inhomogeneous objects as human torso, it is desirable to enhance a natural dielectric contrast.We suggest using ferroelectric nanoparticles for contrast enhancement of MWT. Here we report some of our experimental results of dielectric properties of various ferroelectric nanoparticles and further computer simulations for an assessment of an enhanced diagnostic power of MWT using a simplified chest model with lung cancer. This initial feasibility study demonstrates that ferroelectric nanoparticles might significantly improve a diagnostic power of MWT.
This paper addresses and demonstrates the feasibility for microwave dielectric spectroscopy to detect small volume fractions of SK-MES lung cancer cells embedded in collagen gels with an open-ended coaxial probe. Measurements were performed on the frequency range 200 MHz-2 GHz. For all the cell volume fractions tested (1.4%-4.4%), a significant difference in complex permittivity was observed between composite gels (containing cells) compared to gels alone. Statistically significant changes were especially found in the real part of the permittivity, which decreased consistently when the volume fraction increased.
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