Tissue-mimicking phantom materials for narrowband and ultrawideband microwave applications

Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI 53705, USA.
Physics in Medicine and Biology (Impact Factor: 2.76). 10/2005; 50(18):4245-58. DOI: 10.1088/0031-9155/50/18/001
Source: PubMed

ABSTRACT We propose and characterize oil-in-gelatin dispersions that approximate the dispersive dielectric properties of a variety of human soft tissues over the microwave frequency range from 500 MHz to 20 GHz. Different tissues are mimicked by selection of an appropriate concentration of oil. The materials possess long-term stability and can be employed in heterogeneous configurations without change in geometry or dielectric properties due to osmotic effects. Thus, these materials can be used to construct heterogeneous phantoms, including anthropomorphic types, for narrowband and ultrawideband microwave technologies, such as breast cancer detection and imaging systems.

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    • "Previously, similar recipes of oil-in-gelatine TMPs have been proposed in the literature [14], [18]. However, these recipes include chemicals to lengthen the shelf-life of the TMP. "
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    ABSTRACT: Tissue mimicking phantoms (TMPs) replicating the dielectric properties of wet skin, fat, blood, and muscle tissues for the 0.3 to 20 GHz frequency range are presented in this paper. The TMPs reflect the dielectric properties with maximum deviations of 7.7 units and 3.9 S/m for relative dielectric constant and conductivity, respectively, for the whole band. The dielectric properties of the blood mimicking material are further investigated by adding realistic glucose amounts and a Cole–Cole model used to compare the behavior with respect to changing glucose levels. In addition, a patch resonator was fabricated and tested with the four-layered physical phantom developed in house. It was observed that the input impedance of the resonator is sensitive to the changes in the dielectric properties and, hence, to the realistic glucose level changes in the blood layer.
    IEEE Transactions on Antennas and Propagation 06/2014; 62(6):3064-3075. DOI:10.1109/TAP.2014.2313139 · 2.18 Impact Factor
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    • "Digital Object Identifier 10.1109/LAWP.2014.2312925 created an ultrawideband TMM using a gelatin-in-oil dispersion [10]. By varying the ratio of oil to water, this TMM mimics the dispersive dielectric properties of a variety of human tissues from 500 MHz to 20 GHz. "
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    ABSTRACT: Emerging biomedical applications require realistic phantoms for validation and testing of prototype systems. These phantoms require stable and flexible tissue-mimicking materials with realistic dielectric properties in order to properly model human tissues. To create a tissue-mimicking material to fulfill these needs, carbon powder and urethane rubber mixtures were created, and the dielectric properties were measured using a dielectric probe. Both graphite and carbon black were tested. Mixtures of graphite and urethane (0% to 50% by weight) provided relatively low permittivity and conductivity, suitable for mimicking fatty tissues. Mixtures of carbon black and urethane (0% to 15% by weight) provided a broad range of suitable properties. Samples with 15% carbon black had permittivity and conductivity similar to higher-water-content tissues, however the cured samples were not mechanically suitable for moulding into complex shapes. Finally, mixtures of graphite, carbon black, and urethane were created. These exhibited a range of dielectric properties and can be used to mimic a variety of soft tissues. The mechanical properties of these samples were tested and presented properties that exceed typical phantom requirements. This tissue-mimicking material will be useful when creating thin, flexible, and robust structures such as skin layers.
    IEEE Antennas and Wireless Propagation Letters 01/2014; 13:599-602. DOI:10.1109/LAWP.2014.2312925 · 1.58 Impact Factor
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    • "To our best knowledge, none of the phantom materials used in these needle insertion studies mimic thermal damage to tissue and are limited to simulating mechanical and imaging properties of tissue. Though not used for needle insertion studies, thermal sensitive phantoms were used for thermal therapy studies using the following materials: polyacrylamide [11,16–18], gelatin [19], agar [20], and carrageenan [21]. Among these, according to Bu-Lin et al. [16], polyacrylamide has several advantages such as (a) stable up to temperatures of 100 • C, (b) specific heat capacity and thermal conductivity similar to tissue, (c) high optical transparency at room temperature and ivory white visualization of the heated area, (d) long-term stability, and (e) ease of preparation. "
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    ABSTRACT: This study presents a polyacrylamide gel as a phantom material for needle insertion studies specifically developed for self-actuating needles to enhance the precise placement of needles in prostate. Bending of these self-actuating needles within tissue is achieved by Nitinol actuators attached to the needle body; however these actuators usually involve heating that can thermally damage the tissue surrounding the needles. Therefore, to develop and access feasibility of these needles, a polyacrylamide gel has been developed that mimics the thermal damage and mechanical properties of prostate tissue. Mechanical properties of the polyacrylamide gel was controlled by varying the concentrations of acrylamide monomer and N,N-methylene-bisacrylamide (BIS) cross-linker, and thermal sensitivity was achieved by adding bovine serum albumin (BSA) protein. Two polyacrylamide gels with different concentrations were developed to mimic the elastic modulus of the tissue. The two phantoms showed different rupture toughness and different deflection of bevel-tip needle. To study the thermal damage, a Nitinol wire was embedded in the phantom and resistively heated. The measured opaque zone (0.40mm) formed around the wire was close to the estimated damage zone (0.43mm) determined using the cumulative equivalent minutes at 43°C.
    Medical Engineering & Physics 08/2013; 36(1):140-145. DOI:10.1016/j.medengphy.2013.07.004 · 1.83 Impact Factor
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