| The diagnosis of breast caner at its early stage will lead to longest survival and reduce the breast cancer mortality significantly. Technologies for early breast cancer detection have been eagerly desired for years. High-resolution ultra-wide band (UWB) microwave imaging has many desirable properties of an ideal early breast cancer screener being safe, comfortable, inexpensive and specific (to cancers), it has the potentials to become a viable alternative to conventional X-ray mammography. In this dissertation, we try to propose a new UWB microwave imaging scheme for hemispherical breast model. In this scheme, separated transmitting and receiving antennas are used to bypass the strict request in designing UWB probing antennas and confocal imaging algorithm for our scheme is also developed. Imaging results based on FDTD simulation show the feasibility of our scheme in the detection of early breast cancer of radius smaller than 10mm.In order to reduce the strong reflection from air-skin interface, the coupling medium is suggested to use in practical UWB microwave imaging scheme. The effect of coupling medium on resolution and the general principle for selecting coupling medium are also discussed. In practical breast survey, several tumors with different position may exist, the survey scheme with single source will allocates the energy to each tumor unfairly, so an improved multi-look method was suggested and imaging results show that multi-look method can detect all the tumors more clearly and effectively. The resolution of imaging of the multi-look scheme is also studied and a range for cross-resolution is provided. Furthermore, we ameliorate the breast model to be more realistic with some ducts and glandular tissues in randomly inhomogeneous breast tissue, and the imaging results show that our scheme and algorithm for early breast cancer imaging keep valid for breast tissue with random variations of ± 10% around the normal values. |
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