Parallel-detection microwave spectroscopy system for breast imaging

A liquid-coupled, noncontacting, broadband microwave imaging system has been designed and fabricated. Extension of the operating bandwidth allows us to exploit the potential of new clinical information for breast cancer diagnosis at frequencies higher than previously achieved. The new system design implements a parallel-detection scheme that allows signals to be simultaneously sampled at multiple receiving antenna sites (in 8 s for a single tomographic slice at a single frequency). It also has important features such as high cross-channel isolation (>120 dB), smooth broad bandwidth receiver response, and adjustable intermediate frequency signal amplification factors of 1 to 2000 to ensure successful realization of a large linear dynamic range which is especially important to counteract the increased signal loss at the higher operating frequencies. The new system is capable of recovering dielectric properties of breastlike phantoms with tumor inclusions over the frequency range from 0.5 to 2.1 GHz when embedded in an 87%/13% glycerin/water background. Errors in the measurement data are less than 0.5% in signal amplitude and 1° in phase, on average.