Dielectric characterization of diseased human trabecular bones at microwave frequency

Bilal Amin,Atif Shahzad,Laura Farina,Eoin Parle,Laoise Mcnamara,Martin O'Halloran,Muhammad Adnan Elahi

doi:10.1016/j.medengphy.2020.01.014

Abstract

The objective of this study is to determine whether in vitro dielectric properties of human trabecular bones, can distinguish between osteoporotic and osteoarthritis patients’ bone samples. Specifically this study enlightens intra-patient variation of trabecular bone microarchitecture and dielectric properties, inter-disease comparison of bone dielectric properties, and finally establishes the correlation to traditional bone histomorphometry parameter (bone volume fraction) for diseased bone tissue. Bone cores were obtained from osteoporotic and osteoarthritis patients (n = 12). These were scanned using microCT to examine bone volume fraction. An open-ended coaxial probe measurement technique was employed to measure dielectric properties over the 0.5 – 8.5 GHz frequency range. The dielectric properties of osteoarthritis patients are significantly higher than osteoporotic patients; with an increase of 41% and 45% for relative permittivity and conductivity respectively. The dielectric properties within each patient vary significantly, variation in relative permittivity and conductivity was found to be greater than 25% and 1.4% respectively. A weak correlation (r = 0.5) is observed between relative permittivity and bone volume fraction. Osteoporotic and osteoarthritis bones can be differentiated based on difference of dielectric properties. Although these do not correlate strongly to bone volume fraction, it should be noted that bone volume fraction is a poor predictor of fracture risk. The dielectric properties of bones are found to be influenced by mineralization levels of bones. Therefore, dielectric properties of bones may have potential as a diagnostic measure of osteoporosis.

Highlights

The phenomena of electromagnetic (EM) wave reflection and propagation through biological tissues can be characterized by dielectric properties namely, the relative permittivity and conductivity [1]
Twenty-three bone samples were obtained from osteoporotic patients and twenty-two bone samples were obtained from osteoarthritis patients
We have presented the analysis on: BV/TV of osteoporotic and osteoarthritis bone samples, an analysis on intra-patient variation of bone dielectric properties, dielectric properties of osteoporotic and osteoarthritis bone samples, relationship between dielectric properties and BV/TV, and a comparison of the current study’s findings with the literature

Summary

Introduction

The phenomena of electromagnetic (EM) wave reflection and propagation through biological tissues can be characterized by dielectric properties namely, the relative permittivity and conductivity [1]. Dielectric properties of biological tissues have formed the basis for the development of a number of EM diagnostic and therapeutic medical devices [2], [3]. Some applications of dielectric properties of biological tissues include microwave hyperthermia for breast cancer treatment [4], microwave imaging for breast health monitoring [5] and microwave ablation for treating liver, lung, kidney and adrenal tumours [6], [7]. It has been proposed that the dielectric properties of bones can be used to monitor osteoporosis [9], [10]. Bone dielectric properties are influenced by mineralization and it was proposed that a dielectric property based medical device could diagnose osteoporosis [8], albeit that this has never been established

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