Microwave Imaging for Diagnostic Application

Imaging of the human body makes a significant contribution to the diagnosis and succeeding treatment of diseases. Among the numerous medical imaging methods, microwave imaging (MWI) is an attractive approach for medical applications due to its high potential to produce images of the human body safely with cost-efficiency.
A wide range of studies and research has been done with the aim of using the microwave approach for medical applications.
The focus of this research is developing MWI algorithms, which is the Huygens Principle (HP) based and to validate the capability of the proposed MWI algorithm to detect skin cancer and bone lesion through phantom measurements.
The probability of the HP procedure for skin cancer detection has been investigated through design, and fabrication of a heterogeneous phantom simulating the human forearm having an inclusion mimicking a skin cancer. Ultrawideband (UWB) MWI methods are then applied to the phantom. The S21 parameter measurements are collected in an anechoic chamber environment and processed via HP technique. The tumour is successfully detected after applying appropriate artefact removal procedure.
The ability to successfully apply HP to detect and locate a skin cancer type inclusion in a multilayer cylindrical phantom has been verified.
The feasibility study of HP-based MWI procedure for bone lesion detection has also been investigated using a dedicated phantom. Validation has been completed through measurements inside the anechoic chamber in the frequency range of 1–3 GHz using one receiving and one transmitting antennas in free space. The identification of the lesion’s presence in different bone layers has been performed on images. The quantification of the obtained images has been performed by introducing parameters such as the resolution and signal-to-clutter ratio (S/C). The impact of different frequencies and bandwidths (in the 1–3 GHz range) in lesion detection has been investigated. The findings showed that the frequency range of 1.5–2.5 GHz offered the best resolution (1.1 cm) and S/C (2.22 on a linear scale). Subtraction between S21 obtained using two slightly displaced transmitting positions has been employed to remove the artefacts; the best artefact removal has been obtained when the spatial displacement was approximately of the same magnitude as the dimension of the lesion.
Subsequently, a phantom validation of a low complexity MWI device (based on HP) operating in free space in the 1-6.5 GHz frequency band using two antennas in free space has been applied. Detection has been achieved in both bone fracture lesion and bone marrow lesion scenarios using superimposition of five doublet transmitting positions after applying the rotation subtraction method to remove artefact. A resolution of 5 mm and the S/C (3.35 in linear scale) are achieved which is clearly confirming the advantage of employing multiple transmitting positions on increased detection capability.
The finding of this research verifies the dedicated MWI device as a simple, safe and without any X-ray radiation, portable, and low complexity method, which is capable of been successfully used for bone lesion detection.
The outcomes of this thesis may pave the way for the construction of a dedicated bone imaging system that in future could be used as a safe diagnostic device even in emergency sites.