Simulation and Experimental Measurements for Near Field Imaging

Abstract| Near fleld imaging using microwaves in medical applications has gained much atten-tion recently as various researchers have shown its capability and accuracy in identifying featuresof interest compared to better known screening tools. This paper documents the developmentof system primarily for microwave imaging applications such as breast cancer detection. Whenthe performance of the prototype is tested and analyzed experimentally it exhibits reasonableagreement with simulations.1. INTRODUCTION Breast cancer is the most common non-skin related malignancy and the second leading cause ofcancer death among women in the world every year thousands of women die from the disease [1,2].Until research uncovers a way to prevent breast cancer, early detection will be the best hope forreducing mortality from this disease. X-ray mammography has proved to be a most efiective tooland plays an important role in early breast cancer detection, but despite providing a high percentageof successful detection compare to other screening tools, X-ray mammography has limitations.The uncomfortable breast compression associated with this diagnosis method mitigates againstpatients undergoing early stage examination and both false positive and negative rates have beenreported [2,3] which suggests a need for alternative screening. Exposure to ionizing radiation fromX-rays is also a concern.These factors have motivated a search for a better solution and one possibility under investiga-tion is microwave imaging, a technology whose applications for diagnostic purposes in the fleld ofbiomedical engineering are increasing. Based on variation in dielectric properties, this techniquepromises non-destructive evaluation of biological tissue, and the creation of images related to theelectrical properties of the breast tissue. The tissue of a malignant tumor has higher water con-tent than normal breast tissue and hence markedly difierent dielectric properties [4]. As result,strong scattering take place when the microwaves hit the tumor. Several applications of microwaveimaging in the medical fleld have been recorded and implemented for breast cancer detection [3{8].In this paper we present an experimental system with time domain microwave imaging. First wediscuss the breast phantom used to mimic the conductivity and relative permittivity of actual breasttissue. A previously designed microstrip patch antenna with air as dielectric with a rectangularpatch mounted on two vertical plates, with the ground size 40