Miniaturised Microwave Biosensor Conception and Implementation for Carotid Atherosclerosis Diagnosis

Abstract

Microwave imaging has gained significant attention in the field of medical imaging due to its ability to penetrate through the body and differentiate the dielectric properties of human tissues and hence distinguish abnormal tissues from healthy ones. This thesis uses a miniaturized microwave biosensor that can quantify the relative permittivity of biological tissues. This kind of biosensor exhibits desirable features such as portability, simplicity of design, low cost, and lack of risk to the healthcare provider and the patient. This miniaturized CSRR biosensor has been developed to quantify the composition of atherosclerotic plaques in the carotid artery locally. Initial tests with the sensor were performed on fifty carotid artery atherosclerotic plaques. Histological analysis of those lesions, CT and ultrasound scanning of the corresponding patients were performed to validate the sensor's findings. A comprehensive statistical analysis was performed to correlate the microwave results to histology and compare them with current radiological modalities. In addition, the biosensor was employed to characterize a variety of animal biological tissues representing the human neck model. Thereupon it was tested on a human neck phantom. Preliminary data were compared with results from electromagnetic modelling and 3D simulations of the biosensor loaded by the tested materials. Since the original sensor prototype was designed on a high-loss substrate, it had limited detection depth. Therefore, further CSRRs better suited to detecting in deeper tissues were developed simultaneously. The simulation results for the microwave biosensor were almost equivalent to the actual data. Results showed that the microwave biosensor could distinguish between high-risk and low-risk carotid plaques and characterize individual biological layers but lacked precision for multilayer models. Despite facing several constraints, the miniaturized microwave biosensor can differentiate between diverse biological tissues. With the identification of the issues and obstacles, there is a possibility that a device suitable for in-vivo use in healthcare settings can be manufactured in the near future.