On the matching medium for microwave-based medical diagnosis

Abstract

In microwave-based medical diagnosis, reflections of electromagnetic waves from the air-skin interface can be reduced with a proper choice of matching medium such that electromagnetic radiation can be effectively penetrated into and through human bodies. Due to the heterogeneous and lossy nature of tissue and the fact that the electromagnetic problem varies as a function of matching medium, frequency, incident angles and polarization, it is not trivial to analyze the entire propagation phenomena. In this study, transmission of electromagnetic wave through a multi-layer planar human tissue model with different matching medium is considered. The reflected, absorbed and transmitted power components are computed to quantify the transmission performance of the matching medium. Our results show that although reflection can be minimized through a proper choice of matching medium, it does not necessary result in an optimal transmission as the transmitted signal is severely attenuated inside the tissue. Our results also show that the oblique incidence plane wave components, which in general correspond to the non-zero spatial frequency components of a near field distribution, can better penetrate through the tissue when a low-permittivity matching medium is used. These findings suggest that a better signal integrity can be obtained when a low-permittivity matching medium ( r e between 5 and 30) is used.

On the matching medium for microwave stroke diagnosis

“…When a large number of layers is considered, for instance in stroke diagnosis, the number of tissue layers is much larger and we are not sure if our findings in [29] are still valid. With this in mind, the first objective of this study is to figure out if the conclusions in [29] is still applicable to a realistic multi-layer brain tissue model. The brain model that is made up of at least 17 layers of dielectrics and 8 different tissues (skin, skull, fat, muscle, CSF, gray matter, white matter, blood (bleeding) [11,12]) will be used and the transmission behavior under different settings will be studied.…”

“…To address this issue, our previous study [29] first investigated the amount of transmitted, reflected and absorbed power in a simple planar human tissue model under different incident angles and polarizations. Comparing normal and oblique incidence, our results show that a larger amount of power can be transmitted through the tissue model under normal incidence.…”

“…The findings in [29] are limited to the simple threelayer and five-layer human tissue models. When a large number of layers is considered, for instance in stroke diagnosis, the number of tissue layers is much larger and we are not sure if our findings in [29] are still valid.…”

“…The findings in [29] are limited to the simple threelayer and five-layer human tissue models. When a large number of layers is considered, for instance in stroke diagnosis, the number of tissue layers is much larger and we are not sure if our findings in [29] are still valid. With this in mind, the first objective of this study is to figure out if the conclusions in [29] is still applicable to a realistic multi-layer brain tissue model.…”

Machine Learning-Based Matching Medium Design for Implant Communications

“…As for the studies investigating the optimum relative permittivity for a specific case, the optimum relative permittivity is often determined for different tissue types via analytical studies or repeated numerical analyses. For instance, analytical studies that focus on the determination of the optimum relative permittivity for medical microwave applications are presented in [22]- [24]. However, all these studies assume the wave to be a plane wave, ignoring the near-field losses.…”