Development of a Stationary Digital Breast Tomosynthesis System for Clinical Applications

Digital breast tomosynthesis (DBT) has been shown to be a very beneficial tool in the fight against breast cancer. However, current DBT systems have poor spatial resolution compared to full field digital mammography (FFDM), the current gold standard for screening mammography. The poor spatial resolution of DBT systems is a result of the single X-ray source design. In DBT systems a single X-ray source is rotated over an angular span in order to acquire the images needed for 3D reconstruction. The rotation of the X-ray source degrades the spatial resolution of the images. DBT systems which are approved for use in the United States for screening mammography are required to also take a full field digital mammogram with every DBT acquisition in order to compensate for the poor spatial resolution. This double exposure essentially doubles the radiation dose to patients. Over the past few years our research group has developed a carbon nanotube (CNT) based X-ray source technology. The unique nature of CNT X-ray sources allows for multiple X-ray focal spots in a single X-ray source. Using this technology we have recently developed a stationary DBT system (s-DBT) system which is capable of producing a full tomosynthesis image dataset with zero motion of the X-ray source. This system has been shown to have increased spatial resolution over other DBT systems in a laboratory setting. The goal of this thesis work was to optimize the s-DBT system, demonstrate its usefulness over other systems, and finally implement it into the clinic for a clinical trial. The s-DBT system was optimized using different image quality measurements. The optimized system was then used in a breast specimen imaging trial which compared s-DBT to magnified 2D mammography and a conventional single source DBT system. Readers preferred s-DBT to magnified 2D mammography for specimen margin delineation and mass detection, these results were not significant. Using physical measures for spatial resolution the s-DBT system was shown to have improved image quality over conventional single source DBT systems in breast tissue. A separate study showed that s-DBT could be a feasible alternative to FFDM for screening patients with breast implants. Finally, a second s-DBT system was constructed and implemented into the Department of Mammography at UNC hospitals. The first patient was imaged on the system in December of 2013.Doctor of Philosoph

Astronomical Signatures of Dark Matter

Several independent astronomical observations in different wavelength bands reveal the existence of much larger quantities of matter than what we would deduce from assuming a solar mass to light ratio. They are very high velocities of individual galaxies within clusters of galaxies, higher than expected rotation rates of stars in the outer regions of galaxies, 21 cm line studies indicative of increasing mass to light ratios with radius in the halos of spiral galaxies, hot gaseous X-ray emitting halos around many elliptical galaxies, and clusters of galaxies requiring a much larger component of unseen mass for the hot gas to be bound. The level of gravitational attraction needed for the spatial distribution of galaxies to evolve from the small perturbations implied by the very slightly anisotropic cosmic microwave background radiation to its current web-like configuration requires much more mass than is observed across the entire electromagnetic spectrum. Distorted shapes of galaxies and other features created by gravitational lensing in the images of many astronomical objects require an amount of dark matter consistent with other estimates. The unambiguous detection of dark matter and more recently evidence for dark energy has positioned astronomy at the frontier of fundamental physics as it was in the 17th century

Manipulation of electrospun fibres in flight: the principle of superposition of electric fields as a control method

This study investigates the magnitude of movement of the area of deposition of electrospun fibres in response to an applied auxiliary electric field. The auxiliary field is generated by two pairs of rod electrodes positioned adjacent and parallel to the line of flight of the spun fibre. The changes in shape of the deposition area and the degree of movement of the deposition area are quantified by optical scanning and image analysis. A linear response was observed between the magnitude of movement of the deposition area and voltage difference between the auxiliary and deposition electrodes. A squeezing effect which changed the aspect ratio of the deposition area was also observed to result from the application of symmetric electrical fields. Statistical analysis showed that the deflection and squeezing responses can be thought of as independent control actions. The results from this experiment suggest this particular application of superposition of electric fields could be used as to control the flight path of an electrospun fibre

Direct Detection of Warm Dark Matter in the X-ray

We point out a serendipitous link between warm dark matter (WDM) models for structure formation on the one hand and the high sensitivity energy range (1-10 keV) for x-ray photon detection on the Chandra and XMM-Newton observatories on the other. This fortuitous match may provide either a direct detection of the dark matter or exclusion of many candidates. We estimate expected x-ray fluxes from field galaxies and clusters of galaxies if the dark matter halos of these objects are composed of WDM candidate particles with rest masses in the structure formation-preferred range (~1 keV to ~20 keV) and with small radiative decay branches. Existing observations lead us to conclude that for singlet neutrinos (possessing a very small mixing with active neutrinos) to be a viable WDM candidate they must have rest masses < 5 keV in the zero lepton number production mode. Future deeper observations may detect or exclude the entire parameter range for the zero lepton number case, perhaps restricting the viability of singlet neutrino WDM models to those where singlet production is driven by a significant lepton number. The Constellation X project has the capability to detect/exclude singlet neutrino WDM for lepton number values up to 10% of the photon number. We also consider diffuse x-ray background constraints on these scenarios. These same x-ray observations additionally may constrain parameters of active neutrino and gravitino WDM candidates.Comment: 11 pages, 6 figures, replacement to match ApJ versio

A RANDOMIZED, DOUBLE-BLIND CLINICAL TRIAL COMPARING THE 22 VERSUS 26 GAUGE NEEDLE IN THE PRODUCTION OF THE POST-LUMBAR PUNCTURE SYNDROME IN NORMAL INDIVIDUALS

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73449/1/j.1526-4610.1972.hed1202073.x.pd

Fifteen Years of Chandra Operation: Scientific Highlights and Lessons Learned

NASA's Chandra X-Ray Observatory, designed for three years of operation with a goal of five years is now entering its 15-th year of operation. Thanks to its superb angular resolution, the Observatory continues to yield new and exciting results, many of which were totally unanticipated prior to launch. We discuss the current technical status, review recent scientific highlights, indicate a few future directions, and present what we feel is the most important lesson learned from our experience of building and operating this great observatory

Supplement to Christian Chronicle, May 10, 1968

A supplement to the Christian Chronicle, this special issue contains a report of the Race Relations Workshop held March 4-8, 1968, in Nashville, Tennessee at Schrader Lane Church of Christ. Included are full texts of speeches delivered by the workshop theme speakers: David Jones, Jr., Lawrence L. (Bud) Stumbaugh, James Dennis, Sr., Don Finto, leon Hill, Phillip Roseberry, Joseph Tucker, Joe Tomlinson, Perry Wallace, Jim Mayo, Walter E. Burch, and an article by David Lipscomb condensed from the February 21, 1878 Gospel Advocate

Assessing the risk of stress in organizations:Getting the measure of organizational-level stressors

Great Britain’s Health and Safety Executive (HSE) developed the Management Standards Indicator Tool to help organizations to assess and monitor organizational risks of work-related stress through surveying employees about the psychosocial risks for stress in their jobs. The use of employee-level data for deriving an organizational-level measure of psychosocial risks assumes that the constructs have equivalent meanings at different levels. However, this isomorphic condition has never been tested and this study fills this gap. Using data collected by the Italian Workers’ Compensation Authority (INAIL) from 66,188 employees nested in 775 organizations, we demonstrate that the organizational-level measure representing the seven dimensions of the Management Standards Indicator Tool is equivalent, though not identical, to the individual-level measure. This implies that the organizational level is not a mirror of the aggregation of the individual level, and that the risk of work-related stress in an organization may derive not simply from bottom-up processes, but may be generated by top-down influences (e.g., organizational policies). Interventions may then be meaningfully targeted at the organizational level in the expectation that they will reduce the risk of work-related stress among the entire workforce, the valid measurement of which can be performed through the HSE’s Management Standards Indicator Tool

Peroxisome proliferator-activated receptor gamma and spermidine/spermine N(1)-acetyltransferase gene expressions are significantly correlated in human colorectal cancer

BACKGROUND: The peroxisome proliferator-activated receptor γ (PPARγ) is a transcription factor that regulates adipogenic differentiation and glucose homeostasis. Spermidine/spermine N(1)-acetyltransferase (SSAT) and ornithine decarboxylase (ODC) are key enzymes involved in the metabolism of polyamines, compounds that play an important role in cell proliferation. While the PPARγ role in tumour growth has not been clearly defined, the involvement of the altered polyamine metabolism in colorectal carcinogenesis has been established. In this direction, we have evaluated the PPARγ expression and its relationship with polyamine metabolism in tissue samples from 40 patients operated because of colorectal carcinoma. Since it is known that the functional role of K-ras mutation in colorectal tumorigenesis is associated with cell growth and differentiation, polyamine metabolism and the PPARγ expression were also investigated in terms of K-ras mutation. METHODS: PPARγ, ODC and SSAT mRNA levels were evaluated by reverse transcriptase and real-time PCR. Polyamines were quantified by high performance liquid chromatography (HPLC). ODC and SSAT activity were measured by a radiometric technique. RESULTS: PPARγ expression, as well as SSAT and ODC mRNA levels were significantly higher in cancer as compared to normal mucosa. Tumour samples also showed significantly higher polyamine levels and ODC and SSAT activities in comparison to normal samples. A significant and positive correlation between PPARγ and the SSAT gene expression was observed in both normal and neoplastic tissue (r = 0.73, p < 0.0001; r = 0.65, p < 0.0001, respectively). Moreover, gene expression, polyamine levels and enzymatic activities were increased in colorectal carcinoma samples expressing K-ras mutation as compared to non mutated K-ras samples. CONCLUSION: In conclusion, our data demonstrated a close relationship between PPARγ and SSAT in human colorectal cancer and this could represent an attempt to decrease polyamine levels and to reduce cell growth and tumour development. Therefore, pharmacological activation of PPARγ and/or induction of SSAT may represent a therapeutic or preventive strategy for treating colorectal cancer