IMPORTANCE OF USING A REDUCED CONTRAST COUPLING MEDIUM IN 2D MICROWAVE BREAST IMAGING

Abstract

Microwave imaging of the breast presents unique opportunities for tumor detection when compared with imaging of other anatomical sites. Because of the low permittivity of the breast relative to malignant tumors which are generally believed to be closer to that of biological saline due to rapid metabolism of the cancerous cells and associated angiogenesis, the contrast between normal and malignant breast tissue is considerably higher than that for other anatomical sites. However, the very same low permittivity of the breast presents significant challenges in terms of imaging. A lossy, permittivity—compatible liquid coupling medium is generally needed for medical microwave imaging, with saline being the most convenient for many sites—electrically because of its low contrast with the predominantly high water-content of the body, and economically because of its low cost and suitability for human contact. For breast imaging, a much lower permittivity liquid is required which must be environmentally safe and low in cost. We have been studying organic compounds and the degree to which their electrical properties can be controlled by dilution with varying fractions of saline. Initial 2D simulation and phantom experiments with reduced permittivity coupling mixtures have demonstrated significant improvements where previous limitations had been identified, including: (a) reduction of 3D wave propagation image artifacts, (b) reduction of the effective imaging slice thickness, (c) improvement in property characterization for large, low permittivity scatterers, and (d) enhancement of inclusion detection and artifact reduction. Results illustrating these improvements are presented here including a set of actual patient images and represent important milestones for clinical system development.

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