45 research outputs found

    Novel Ultrasound Elastography Imaging System for Breast Cancer Assessment

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    Abstract Most conventional methods of breast cancer screening such as X-ray, Ultrasound (US) and MRI have some issues ranging from weaknesses associated with tumour detection or classification to high cost or excessive time of image acquisition and reconstruction. Elastography is a non- invasive technique to visualize suspicious areas in soft tissues such as the breast, prostate and myocardium using tissue stiffness as image contrast mechanism. In this study, a breast Elastography system based on US imaging is proposed. This technique is fast, expected to be cost effective and more sensitive and specific compared to conventional US imaging. Unlike current Elastography techniques that image relative elastic modulus, this technique is capable of imaging absolute Young\u27s modulus (YM). In this technique, tissue displacements and surface forces used to mechanically stimulate the tissue are acquired and used as input to reconstruct the tissue YM distribution. For displacements acquisition, two techniques were used in this research: 1) a modified optical flow technique, which estimates the displacement of each node from US pre- and post-compression images and 2) Radio Frequency (RF) signal cross-correlation technique. In the former, displacements are calculated in 2 dimensions whereas in the latter, displacements are calculated in the US axial direction only. For improving the quality of elastography images, surface force data was used to calculate the stress distribution throughout the organ of interest by using an analytical model and a statistical numerical model. For force data acquisition, a system was developed in which load cells are used to measure forces on the surface of the breast. These forces are input into the stress distribution models to estimate the tissue stress distribution. By combining the stress field with the strain field calculated from the acquired displacements using Hooke\u27s law, the YM can be reconstructed efficiently. To validate the proposed technique, numerical and tissue mimicking phantom studies were conducted. For the numerical phantom study, a 3D breast-shape phantom was created with synthetic US pre- and post-compression images where the results showed the feasibility of reconstructing the absolute value of YM of tumour and background. In the tissue mimicking study, a block shape gelatine- agar phantom was constructed with a cylindrical inclusion. Results obtained from this study also indicated reasonably accurate reconstruction of the YM. The quality of the obtained elasticity images shows that image quality is improved by incorporating the adapted stress calculation techniques. Furthermore, the proposed elastography system is reasonably fast and can be potentially used in real-time clinical applications

    Noncontact Three-Dimensional Diffuse Optical Imaging of Deep Tissue Blood Flow Distribution

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    The present invention provides for three-dimensional reflectance diffuse optical imaging of deep tissue blood flow distribution that removes the need for probe-tissue contact, thereby allowing for such technology to be applied to sensitive, vulnerable, damaged, or reconstructive tissue. The systems utilize noncontact application and detection of near-infrared light through optical lens and detection through a linear array or two-dimensional array of avalanche photodiodes or a two-dimensional array of detectors provided by charge-coupled-device (CCD). Both further feature a finite-element-method (FEM) based facilitation to provide for three-dimensional flow image reconstruction in deep tissues with arbitrary geometries

    Vermessung, Modellierung und Verifizierung von Licht-Masse-Interaktions-Phänomenen

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    The photo-realistic rendering of scenes showing natural phenomena requires skilled graphic designers not only to produce a convincingly good-looking image but also to convey physical plausibility. This is especially important in industrial context, where a modelled scene showcasing a product has to approximate the actual environment of a product as closely as possible, e.g. in automotive industries. In this thesis, new techniques to measure natural phenomena are presented in order to provide new or verify existing models for rendering the physically plausible image. In contrast to other approaches, the measurement is performed using nonconventional methods: an ellipsometer is employed to capture the specular reflectance with respect to the polarisation behaviour, a transmissive screen attached to a glass tank is imaged to capture underwater reflectances, and the Microsoft Kinect, a motion capturing device, is used to detect the gas flows around objects. The results are the verification of existing, physically plausible models for commodity metals, an enhanced reflectance model for materials immersed in transparent media with known refractive index, and the reconstruction of two-phase gas flows around occluding objects.Das Erzeugen von Szenen mit natürlichen Phänomenen in fotorealistischer Qualität ist aufwändig, weil nicht nur ein realistisches Bild erstellt werden soll, sondern auch physikalische Plausibilität in Bezug auf das modellierte Phänomen verlangt wird. Besonders in der Industrie, z.B. in der Automobilindustrie, sollte die modellierte Szene, in der ein Produkt eingesetzt wird, der tatsächlichen Einsatzumgebung so naturgetreu wie möglich ähneln. In dieser Dissertation werden neue Ansätze zum Messen von natürlichen Phänomenen präsentiert, die es ermöglichen, für bestimmte Phänomene neue Modelle zu erstellen oder bestehende Modelle erschöpfender zu verifizieren, um damit physikalische Plausibilität für Szenen, die am Computer ereugt werden, zu gewährleisten. Im Unterschied zu anderen Verfahren, werden unkonventionelle Methoden zur Messung umgesetzt: Mit Hilfe eines Ellipsometers wird die Oberflächenreflektanz von Metallen so vermessen, dass auch Änderungen im Polarisationszustand des Lichtes erfasst werden. Unterwasserreflektanzen von Materialien werden mit Hilfe eines lichtdurchlässigen Diffusers abgebildet, der an einen Glasbecher angebracht wird, und der Bewegungssensor Kinect von Microsoft wird verwendet, um Gasströmungen um Objekte zu detektieren. Die Ergebnisse sind die Verifikation von bestehenden Modellen für handelsübliche Metallflächen, ein erweitertes Reflektanzmodell für Oberflächen, die in refraktive Medien eingetaucht werden und die Rekonstruktion von Gasströmungen um Objekte

    Turbine Engine Hot Section Technology (HOST)

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    Research and plans concerning aircraft gas turbine engine hot section durability problems were discussed. Under the topics of structural analysis, fatigue and fracture, surface protective coatings, combustion, turbine heat transfer, and instrumentation specific points addressed were the thermal and fluid environment around liners, blades, and vanes, material coatings, constitutive behavior, stress-strain response, and life prediction methods for the three components

    Research and Technology Report. Goddard Space Flight Center

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    This issue of Goddard Space Flight Center's annual report highlights the importance of mission operations and data systems covering mission planning and operations; TDRSS, positioning systems, and orbit determination; ground system and networks, hardware and software; data processing and analysis; and World Wide Web use. The report also includes flight projects, space sciences, Earth system science, and engineering and materials

    Research & Technology Report Goddard Space Flight Center

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    The main theme of this edition of the annual Research and Technology Report is Mission Operations and Data Systems. Shifting from centralized to distributed mission operations, and from human interactive operations to highly automated operations is reported. The following aspects are addressed: Mission planning and operations; TDRSS, Positioning Systems, and orbit determination; hardware and software associated with Ground System and Networks; data processing and analysis; and World Wide Web. Flight projects are described along with the achievements in space sciences and earth sciences. Spacecraft subsystems, cryogenic developments, and new tools and capabilities are also discussed

    Proceedings of ICMMB2014

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    Towards the validation of thermoacoustic modelling in aerospace structures

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    The research presented in this thesis has been performed over the course of three years under funding from the European Office of the United States Air Force (EAORD) as a part of a long-term project to collect high quality data for the validation of computational mechanics models of thermoacoustic loading. The focus is on the adaptation of stereoscopic (3D) Digital Image Correlation for use in a combined thermal and high temperature measurements. To that end, a background is provided which highlights the current state of the art in high temperature, vibration experiments and data acquisition. A system is described in which a pulsed laser of duration 4 nanoseconds is used to capture high-quality displacement and strain data from vibrating components (PL- DIC). Based on this a novel method of capturing data from a component subjected to random excitation was developed. A laser vibrometer was used along with a custom LabVIEW program to trigger the pulsed laser relative to points of maximum velocity in the components vibration cycle. A dynamic calibration procedure was performed of both a high speed DIC system and the Pulsed-Laser DIC system to assess and compare the measurement uncertainty from the respective systems. It is crucial to know the uncertainty in experimental data when using it for the validation of computational models. A new way to validate computational models of vibration behavior using full-field DIC data and image decomposition is described. This is a phasic approach in which data from the entire cycle of vibration is used. The validation assessment is performed using the expanded uncertainty calculated and a concordance correlation coefficient. An example is provided using an aerospace component to validate four different simulation conditions of a modal frequency response model. An apparatus was designed and built which uses a 10 kW array of quartz lamps to reproduce some aspects of the heating provided by the Air Force test chambers. Experiments were performed in collaboration with the University of Illinois using induction heating and a small Hastelloy plate. A thermal buckling phenomena was observed using the PL-DIC system, the first full-field results of such
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