Human head phantom material characterization for microwave imaging system

Abstract

Breast and brain cancers are stated as the most common causes of cancer-related deaths around the world. Recently, microwave imaging has been proposed for breast cancer imaging and diagnosis, and can be extended for brain cancer imaging. However, tissues and cells for human head are different from human breast especially in terms of dielectric properties thus requiring the development of an appropriate head phantom. The required phantom for brain cancer detection system must have particular specification to make it compatible with the imaging system. This thesis presents an investigation on dielectric properties of materials of human head phantom for microwave imaging system. In the investigation, samples of phantoms are made using water and gelatin in producing a cost effective phantom. The scopes of investigation are on the characteristics of water, tissues of phantom, dielectric variation factors, preservation of phantom and lifespan of phantom. This study focuses on dielectric properties consisting of relative permittivity and conductivity across microwave frequency from 1 to 6 GHz. All measurements are obtained using Vector Network Analyzer with a dielectric probe to obtain complex permittivity. Investigation on water characteristics indicate that almost any type of plain water has similar dielectric characteristics. Five compositions of gelatin-based materials presented in this investigation showed to have similar dielectric properties with five human head tissues, which are grey matter (composition of 5g gelatin, 20g water and 0.5g sugar), white matter (composition of 5g gelatin and 14g water), cerebral spinal fluid (composition of 10g gelatin and 50g water), blood (composition of 10g gelatin and 30g water), and skin (composition of 10g gelatin and 20g water). Besides the ratio between water and gelatin, three other factors of temperature, salt and sugar are discovered to be able to change the dielectric properties of the materials in the investigation. The preservation of gelatin-based material is proposed using vinegar and is able to prolong the lifespan of phantom. The outcome in this thesis is useful in gaining knowledge on dielectric characteristics of material used in human head phantom which is important in the stage of developing, tuning and controlling the dielectric properties of the phantom.