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Articles 1 - 7 of 7
Full-Text Articles in Radiology
Phase And Dark Field Radiography And Ct With Mesh-Based Structured Illumination And Polycapillary Optics, Uttam Pyakurel
Phase And Dark Field Radiography And Ct With Mesh-Based Structured Illumination And Polycapillary Optics, Uttam Pyakurel
Legacy Theses & Dissertations (2009 - 2024)
Imaging can be performed with a variety of techniques. For example, gamma radiation is used in nuclear medicine and radiation therapy A challenge in using gamma rays is the risk of high radiation exposure, which requires extensive custom shielding. The transmission of gamma rays through 3D printed shielding was measured to evaluate the required thickness of the shielding.Conventional radiography depends on x-ray attenuation. Another imaging technique, X-ray phase imaging, is known to improve the contrast of images relative to conventional imaging for low density materials. Phase differences imparted by soft tissue are roughly 1000 times larger than attenuation differences. Further, …
System Measurements For X-Ray Phase And Diffraction Imaging, Erik Wolfgang Tripi
System Measurements For X-Ray Phase And Diffraction Imaging, Erik Wolfgang Tripi
Legacy Theses & Dissertations (2009 - 2024)
In medical imaging, X rays are used to look inside the body to find fractures in bones, abnormal masses, cavities in teeth, and so on. What makes X rays so good at looking at these types of structures is the X ray’s penetration power. When imaging soft tissue to search for tumors, X-ray images tend to have difficulty performing well. The reason for this is that the background structures, such as fat or fibro glandular tissue have similar absorption coefficients as the tumor. Mammography tends to have a high false positive rate and can miss tumors entirely as well. There …
Therapy And Medical Imaging Applications Of Focusing Polycapillary X-Ray Optics, Weiyuan Sun
Therapy And Medical Imaging Applications Of Focusing Polycapillary X-Ray Optics, Weiyuan Sun
Legacy Theses & Dissertations (2009 - 2024)
Focusing polycapillary optics yield high gains in intensity and increased spatial resolution for a variety of clinical, lab-based, synchrotron, or in situ analysis applications. In this dissertation we investigate the extension of two applications of focusing polycapillary optics. The first is the application of polycapillary optics in radiation therapy. This discussion includes measurements and calculation of dose for focused beam orthovoltage therapy. A system has been designed to investigate whether the polycapillary optics can produce an X-ray beam which can give more accurate dose painting due to the higher dose concentration at the focal spot. X-ray exposures were measured with …
Phase Imaging Using Focusing Polycapillary Optics, Sajid Bashir
Phase Imaging Using Focusing Polycapillary Optics, Sajid Bashir
Legacy Theses & Dissertations (2009 - 2024)
The interaction of X rays in diagnostic energy range with soft tissues can be described by Compton scattering and by the complex refractive index, which together characterize the attenuation properties of the tissue and the phase imparted to X rays passing through it. Many soft tissues exhibit extremely similar attenuation, so that their discrimination using conventional radiography, which generates contrast in an image through differential attenuation, is challenging. However, these tissues will impart phase differences significantly greater than attenuation differences to the X rays passing through them, so that phase-contrast imaging techniques can enable their discrimination.
Grid-Based Fourier Transform Phase Contrast Imaging, Sajjad Tahir
Grid-Based Fourier Transform Phase Contrast Imaging, Sajjad Tahir
Legacy Theses & Dissertations (2009 - 2024)
Low contrast in x-ray attenuation imaging between different materials of low electron density is a limitation of traditional x-ray radiography. Phase contrast imaging offers the potential to improve the contrast between such materials, but due to the requirements on the spatial coherence of the x-ray beam, practical implementation of such systems with tabletop (i.e. non-synchrotron) sources has been limited. One recently developed phase imaging technique employs multiple fine-pitched gratings. However, the strict manufacturing tolerances and precise alignment requirements have limited the widespread adoption of grating-based techniques. In this work, we have investigated a technique recently demonstrated by Bennett et al.1 …
Potential For High Resolution Microscintigraphy Using Polycapillary Optics, Patrick Richard Conlon
Potential For High Resolution Microscintigraphy Using Polycapillary Optics, Patrick Richard Conlon
Legacy Theses & Dissertations (2009 - 2024)
Scintigraphy, also known as nuclear imaging, is the process of imaging an object that has been labeled with a radioactive material. A novel technique employing polycapillary optics for very high - resolution scintigraphy is presented. The small channel size and angular selectivity of polycapillary optics allow them to act as multiple-hole collimators and be used with high - resolution detectors. The ability of the optics to work with high resolution detectors allow the system to discriminate against scatter, thus negating the need for energy sensitive detectors, which are known to have poor resolution. Therefore the use of polycapillary optics presents …
Application Of X-Ray Diffraction To Material Analysis And Medical Imaging, Wei Zhou
Application Of X-Ray Diffraction To Material Analysis And Medical Imaging, Wei Zhou
Legacy Theses & Dissertations (2009 - 2024)
Powder diffraction is commonly used to determine the structures of both inorganic and organic materials. The angle and intensity of the diffraction (also called coherent scatter) peak depends on the nanostructure of the material. When no x-ray optic is used, the peak width broadens, and hence the resolution worsens, as the sample area is increased. However, a small sample area gives low diffracted signal intensity, particularly for thin films and for organic materials, which have low diffraction cross sections. X-ray optics can be used in x-ray powder diffraction to increase the diffraction intensity, thus decreasing exposure times. For a small …