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IEEE Transactions on Microwave Theory and Techniques 10/2005; 53(9):3053- 3053. · 1.85 Impact Factor
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ABSTRACT: Hermetic stainless-steel open-ended coaxial probes have been designed for precision dielectric spectroscopy of biological tissue, such as breast tissue, over the 0.5-20-GHz frequency range. Robust data-processing techniques have also been developed for extracting the unknown permittivity of the tissue under test from the reflection coefficient measured with the precision probe and a vector network analyzer. The first technique, referred to as a reflection-coefficient deembedding method, converts the reflection coefficient measured at the probe's calibration plane to the desired aperture-plane reflection coefficient. The second technique uses a rational function model to solve the inverse problem, i.e., to convert the aperture-plane reflection coefficient to the tissue permittivity. The results of the characterization and validation studies demonstrate that these precision probes, used with the prescribed measurement protocols and data-processing techniques, provide highly accurate and reliable in vivo and ex vivo biological tissue measurements, including breast tissue spectroscopy.
IEEE Transactions on Microwave Theory and Techniques 06/2005; · 1.85 Impact Factor
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ABSTRACT: A simple treatment of E-field component tangential to dispersive media interfaces in FDTD is introduced. The method uses concepts from the auxiliary differential equations method to average the constitutive parameters. The cases of a wave propagating in a coaxial line and of an open-ended coaxial line radiating into the dispersive media are investigated. Results show that the simulations could be significantly erroneous if the interface is not handled properly.
IEEE Microwave and Wireless Components Letters 08/2003; · 1.72 Impact Factor
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ABSTRACT: Large-scale dielectric spectroscopy of healthy and diseased breast tissue in the 0.1 to 20 GHz frequency range is currently underway. Open-ended coaxial probes are used as sensors to record the reflection coefficient of the tissue samples. The measured reflection coefficient is converted to the dielectric properties data through a suitable inverse technique. The collected data will aid in further advances of the microwave technology for early breast cancer detection. Thus, it is crucial to ensure the highest possible accuracy and reliability of the tissue measurements.
Antennas and Propagation Society International Symposium, 2003. IEEE; 07/2003
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ABSTRACT: To achieve accurate measurements, the tissue sample should be homogeneous within a volume large enough so that the measured reflection coefficient is identical to that of a sample filling the entire half-space. Thus, the question arises of the appropriate size of the tissue sample. Sensing volume guidelines have been previously investigated in terms of somewhat arbitrarily chosen constraints on the relative errors in the measured reflection coefficient of tissue-equivalent liquids. In this paper we report sensing volume guidelines that have been developed by first choosing acceptable levels of error in the permittivity and then deriving the appropriate constraints on the errors in the measured reflection coefficient.
Antennas and Propagation Society International Symposium, 2003. IEEE; 07/2003
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ABSTRACT: We have used open-ended coaxial probes to determine the dielectric properties of freshly excised normal and diseased breast tissue specimens. The considerable variability in size and composition of these specimens predicates the need for determining the minimum surgical specimen size that yields accurate measurements for a given probe diameter. We investigate the sensing volume of 2.2- and 3.58-mm-diameter flange-free coaxial probes for both lowand high-water-content tissue using standard liquids that exhibit dielectric properties similar to breast tissue over the microwave frequency range from 1 to 20 GHz. We also present an innovative graphical technique based on the use of Cole-Cole diagrams to determine the error thresholds in the magnitude and phase of the reflection coefficient, which bound the errors in the measured complex permittivity to an acceptable level. Results from self-consistent experiments and finite-difference time-domain simulations indicate that a tissue specimen with a thickness of 3.0 mm and a transverse dimension of 1.1 cm is the minimum size that yields accurate measurements with the 3.58-mm-diameter probe. For the 2.2-mm-diameter probe, the specimen's thickness and width should be at least 1.5 and 5 mm, respectively. These conclusions are relevant not only to breast tissue characterization, but also more generally to the dielectric characterization of a variety of low- and high-water-content biological tissues.
IEEE Transactions on Microwave Theory and Techniques 05/2003; · 1.85 Impact Factor
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ABSTRACT: A detailed study of dielectric properties of breast tissue in the 0.1 to 20 GHz frequency range currently under way uses open-ended teflon coaxial probes as sensors. This letter quantifies the effects of small mechanical imperfections at the probe aperture on the measured reflection coefficient. The mechanical flaws in the probe can lead to significant errors, thus probes for dielectric spectroscopy of breast tissue have to be carefully manufactured.
IEEE Microwave and Wireless Components Letters 11/2002; · 1.72 Impact Factor
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ABSTRACT: An ultrawideband microwave imaging approach to early breast cancer
detection is based on the hypothesis that there exists a significant
dielectric-properties contrast between cancerous and normal breast
tissue at microwave frequencies. Definitive knowledge of the dielectric
properties of breast tissue in the RF/microwave frequency range (0.1-20
GHz) is required for the development of novel technologies related to
the detection and treatment of breast cancer. Coaxial probes have been
extensively analyzed and used in dielectric spectroscopy. A careful
analysis of the sensing volume of the probes used in our measurements on
excised specimens is needed to ensure the highest possible accuracy in
the dielectric properties estimates of human breast tissue. We present
preliminary estimates of the sensing volume of small diameter coaxial
probes. Results were obtained for 2.20 mm and 3.58 mm diameter probes,
both without flanges. De-ionized water, methanol, and butanol were
chosen as test liquids because their dielectric properties cover the
expected range of permittivities of breast tissue. Our results suggest
that relatively small tissue samples are sufficient to establish
accurately their dielectric properties in the microwave frequency range
up to 20 GHz, using small-diameter open-ended coaxial probes
Antennas and Propagation Society International Symposium, 2001. IEEE; 02/2001
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ABSTRACT: This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
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ABSTRACT: This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.
