RF tomography has great potential in defense and homeland security applications. A distributed sensing research facility is under development at Air Force Research Lab. To develop a RF tomographic imaging system for the facility, preliminary experiments have been performed in an indoor range with 12 radar sensors distributed on a circle of 3m radius. Ultra-wideband pulses are used to illuminate single and multiple metallic targets. The echoes received by distributed sensors were processed and combined for tomography reconstruction. Traditional matched filter algorithm and truncated singular value decomposition (SVD) algorithm are compared in terms of their complexity, accuracy, and suitability for distributed processing. A new algorithm is proposed for shape reconstruction, which jointly estimates the object boundary and scatter points on the waveform’s propagation path. The results show that the new algorithm allows accurate reconstruction of object shape, which is not available through the matched filter and truncated SVD algorithms.
Various medical imaging techniques exist to detect the early development of tissue damage. However, a widely
commercialized device that can be easily used and is cost effective is still needed. Through a literature review, we
examined ultrasound, microwave tomography, and ultra-wideband (UWB) technology. Out of these techniques, UWB is
the most promising since it has the capability to detect small adjustments in dielectric properties, which can change with
minor alterations in perfusion and internal pressure. These minor alterations are vital in detecting the onset of ischemia,
which precedes many serious conditions affecting tissue health. In addition to its ability in detection, UWB also has the
potential to become a widely accessible technology to hospitals. Using software called XFdtd, we simulated ultrawideband
pulses propagating through planes designed to resemble tissue in its dielectric properties. After testing several
sizes of the horn antenna and configurations for the wire and port, the antenna's near field was finally able to reach the
distance necessary to penetrate the tissue model. The resulting graph of voltage versus time was generated from the
received antenna signal and it will be compared to the graphs that result after the dielectric properties of the model have
been changed to simulate tissue injury. Through this manipulation of the tissue model, the sensitivity and selectivity of
UWB in measuring small fluctuations in perfusion can be determined. In this future work with XFdtd, we want to show
that UWB is a novel and viable technique in detecting early tissue injury.