Abstract Purpose: The TomoTherapy planning system is capable of creating treatment plans that deliver a homogeneous dose to superficial targets. It is essential that the planning system accurately predicts dose to the surface and superficial depths from beams directed at every angle in the axial plane. This work concentrates on measuring and modeling the dose from a static TomoTherapy beam at normal and oblique incidence. It was hypothesized that superficial doses measured from a static TomoTherapy beam agree with doses calculated by the TomoTherapy planning system to within 5% of the maximum dose for angles of incidence from 0¢ª-83¢ª. Methods: Doses were measured with a parallel-plate chamber and TLDs at depths ¡Â 2cm for 40x2.5cm2 and 40x5cm2 static TomoTherapy beams for multiple SSDs for incident angles of 0¢ª-83¢ª. The measurements made with TLDs were compared to those made with the parallel-plate chamber to verify the measured dose. The TomoTherapy treatment planning system was used to calculate doses from single, static beams incident on a flat phantom so that measured and calculated doses could be compared. Results: Surface dose increased from 16.7%-18.9% as the SSD decreased from 85 to 55cm for the 40x5cm2 field and from 12.7%-14.9% for the 40x2.5cm2 field. The surface dose increased from 16.8%-44.2% as the angle of incidence increased from 0¢ª-83¢ª for the 40x5cm2 field and from 12.8%-42.6% for the 40x2.5cm2 field. For all measurement conditions, the planning system under predicted the dose at the surface by more than 5%. For the following measurement conditions and depths, the planning system also under predicted the dose by more the 5%: 85 and 70cm SCD at a depth of 0.1cm, 55cm SCD at a depth of 0.2cm, and 30¢ª and 45¢ª at a depth of 0.1cm. For 75¢ª and 83¢ª, the planning system over predicted the dose at superficial depths (0.1cm-0.3cm) by as much as 7%. Conclusions: The results of this work indicate that the planning system under predicted the dose at the surface and superficial depths (depths ¡Â 0.3cm) from a static TomoTherapy beam at both normal and oblique incidence by more than 5%.

Purpose: Segmented-field electron conformal therapy (SFECT) is rarely used, or if used, used sub optimally, primarily due to inadequate tools for its planning. The development of SFECT planning tools could help begin to bring electron therapy to the same level of sophistication as x-ray and proton therapy, resulting in greater consideration by radiation oncologists. The purpose of this work was to develop a forward planning algorithm that will improve segmentation of the SFECT treatment field. It was hypothesized that a forward planning algorithm can produce segmented-field ECT fields that improve dose conformity as the number of beam energies is increased from one to five using the Varian beam set (6, 9, 12, 16, and 20 MeV). Methods: A planning algorithm that allowed each field segment to have its own energy, shape, size, and weighting was developed. The planning algorithm developed an initial plan and then went through several iterations of re-planning based on the dose distributions of each previous plan in order to converge the 90% dose surface to the distal PTV surface. The planning algorithm was used to develop SFECT plans for six hypothetical PTVs and two head and neck patient PTVs. These plans were compared to single-energy plans developed by the same planning algorithm. Results: Conformity improved little beyond allowing three energies due to energy overlap and field-size restrictions. For the hypothetical PTVs, non-PTV treated to 90% of the prescribed dose was reduced compared to the single-energy plans, resulting in improved dose conformity, supporting the hypothesis. The improved conformity came at the expense of increased dose heterogeneity within the PTV. One of the patient plans improved in conformity, supporting the hypothesis and indicating the planning algorithm has the potential to plan patient cases. The other patient case did not improve in conformity and therefore did not support the hypothesis. Conclusion: The planning algorithm was successful in developing plans that improved conformity while still treating the PTV to prescription dose. The planning algorithm has the potential to plan patient SFECT treatments. Future improvements to the algorithm may improve its ability to plan patient cases.

Even though Quantum Chromodynamics (QCD) was formulated over three decades ago, it poses enormous challenges for describing the properties of hadrons from the underlying quark-gluon degrees of freedom. Moreover, the problem of describing the nuclear force from its quark-gluon origin is still open. While a direct solution of QCD to describe the hadrons and nuclear force is not possible at this time, we explore a variety of developed approaches ranging from phenomenology to first principle calculations at one or other level of approximation in linking the nuclear force to QCD. The Dyson Schwinger formulation (DSE) of coupled integral equations for the QCD Greens functions allows a non-perturbative approach to describe hadronic properties, starting from the level of QCD n-point functions. A significant approx- imation in this method is the employment of a finite truncation of the system of DSEs, that might distort the physical picture. In this work we explore the effects of including a more complete truncation of the quark-gluon vertex function on the resulting solutions for the quark 2-point functions as well as the pseudoscalar and vector meson masses. The exploration showed strong indications of possibly large contributions from the explicit inclusion of the gluon 3- and 4-point functions that are omitted in this and previous analyses. We then explore the possibility of ex- trapolating state of the art lattice QCD calculations of nucleon form factors to the physical regime using phenomenological models of nucleon structure. Finally, we further developed the Quark Meson Coupling model for describing atomic nuclei and nuclear matter, where the quark-gluon structure of nucleons is modeled by the MIT bag model and the nucleon many body interaction is mediated by the exchange of scalar and vector mesons. This approach allows us to formulate a fully relativistic theory, which can be expanded in the nonrelativistic limit to repro- duce the well known phenomenological Skyrme-type interaction density functional, thus providing a direct link to well modeled nuclear forces. Moreover, it allows for a derivation of the equation of state for cold uniform dense nuclear matter for application to calculations of the properties of neutron stars.

Purpose: To evaluate the accuracy of electron beam dose calculations in MVCT images containing lead alloy masks. Method and Materials: A phantom consisting of two 30x30x5 cm³ slabs of CIRS plastic water® was imaged using kVCT (GE Lightspeed-RT) and MVCT (TomoTherapy Hi·Art). Nine MVCT scans were taken with different square masks of lead alloy (Cerrobend®, density = 9.4 g·cm^-3) on top of the phantom. The masks contained square apertures of 3x3 cm², 6x6 cm² and 10x10 cm² and had thicknesses of 6 mm, 8 mm and 10 mm. The same collimation was simulated in the kVCT images by creating regions-of-interest (ROI) duplicating the sizes, shapes, and density of the masks. Using the Philips Pinnacle³ treatment planning system, twelve treatment plans were created for the combination of four electron energies (6, 9, 12, and 16 MeV) and the three apertures. For each plan, the mask thickness appropriate for the electron energy was used and the dose distributions calculated using the kVCT and MVCT images were compared. In uniform dose regions dose differences were calculated; in high dose-gradient regions distances-to-agreement (DTA) were measured. Results: In the uniform dose region, the maximum differences of doses in the MVCT images from doses in the kVCT images were greater than or equal to ±5% for all but one opening and energy combination. In the high dose-gradient region, more than half of the maximum DTA values exceeded 2 mm. Analysis of the MVCT images showed that the differences were largely due to two errors. First, the presence of the masks caused distortions in the MVCT numbers such that the calculated dose in the MVCT images penetrated less deeply. Second, distortion in the shape of the image of the collimation caused the calculation algorithm to scatter excess electrons into the central axis of the beam. Conclusion: The presence of Cerrobend® masks in MVCT imaging produces distortions in the CT numbers that make electron beam dose calculations insufficiently accurate for electron beam treatment planning. Supported in part by a research agreement with TomoTherapy, Inc.

Research is presented that was performed to determine possible locations for a full scale Salt Dome Shower Array (SalSA) neutrino telescope sensitive to energies from TeV ($10^{12}$ eV), PeV ($10^{15}$ eV), and EeV ($10^{18}$ eV) neutrinos. A detector to test possible site locations was designed around a half-Watt Ham radio to transmit short pulses of 145.500 MHz radiation. The research began by designing the system. Several phases of design took place as the system was refined and calibrated. Once finished, it was taken into a field and tested. The objective was to determine how the signals depended on distance. In principle, there should have been a linear relationship between distance and voltage. After successful testing, the system will be taken to a salt mine to accurately determine the index of refraction and attenuation length of that particular mine's salt.

The origins and compositions of ultra-high energy cosmic rays (UHECR) remains a mystery to this day. The Pierre Auger Observatory (PAO) is being constructed now in the hopes that it will help solve this mystery by detecting more UHECR than any previous experiment. In this dissertation, I will discuss this experiment, and analyze the data collected so far by comparing it with simulated data from possible source distributions. In these simulations, I will track antiprotons, along with other possible cosmic ray primaries, through various models of galactic and extragalactic magnetic fields. Once they reach a certain distance, I will record their positions on the sky. These final positions will determine the weight of that position on the sky. This weight will then be applied to possible source distributions, and the particles will be reinjected back to the earth's surface, and the simulated arrival directions will be analyzed. I will be using the method of calculating spherical harmonics coefficients to analyze the data. The method of using these angular power spectra is an attempt to provide a common language for model builders and experimentalists. Anisotropies of any size are easily detected using these coefficients, making them an ideal way to look at observed events that might not be coming from single, point sources. I will compare the results of this analysis with data obtained by the PAO by calculating spherical harmonics coefficients. After comparing the events collected to date by the PAO with three possible source distributions-isotropic, Active Galactic Nuclei, and nearby galaxies-I have observed that the data looks consistent with either nearby galaxies or AGNs as sources. However, there does exist an extra dipole moment inherent to a half-sky exposure, such as the PAO currently has, which adds in an uncertainty that fundamentally undermines the capabilities of large-scale anisotropy analysis. In the absence of clear point-like sources, construction of a detector in the Northern hemisphere will be necessary in order to know the origins of UHECRs with any confidence.

A electronically collimated prototype detector was built with commercially available cadmium zinc telluride (CZT) modules and assessed by experiment and simulation. Sensitivity was roughly equivalent to a common hand held 1"x1" NaI(Tl) detector. The maximum useful count rate was 300 counts per second (cps) per module. Overall angular error was less than 7°, which is generally less than source placement uncertainty, and angular resolution was between 20° and 40° for several common isotopes with photon energies between 511 keV and 1333 keV. Prototype data and backprojections were used to verify a simple three dimensional model of charge induction in pixellated CZT using an uncollided flux Monte Carlo code. The goal was to devise a hand held radiation detector that can be made with rugged and commercially available parts that can see a 0.1 mCi source with an energy range of 70 keV to 2 MeV at three meters distance with an annular resolution of less than 25° full width at half maximum (FWHM). The prototype lacked sensitivity to meet this stringent goal but proved the modules and prototype concept useful for a variety of health physics applications.

Purpose: To develop a system for measuring 2D dose distributions in the cranium and to use this system to evaluate the accuracy of coplanar conformal therapy using ExacTrac image guidance. Methods: Techniques were developed to measure dose distributions in each principal plane using a CIRS anthropomorphic head phantom with a custom internal film cassette. Sections of EDR2 film were cut, processed, and digitized using custom templates. Spatial and dosimetric accuracy and precision of the film system was assessed. BrainScan was used to plan a coplanar-beam treatment conforming to irradiate a 2-cm diameter x 2-cm cylindrical target. Prior to delivery phantom misalignments were imposed in combinations of ±8-mm offsets in each of the principal directions. ExacTrac X-ray correction was applied until the phantom was within an acceptance criteria of 1mm-1° (first two measurement sessions) or 0.4mm-0.4º (last two measurement sessions). Measured dose distributions on film were registered to the treatment plan and compared. Results: Alignment errors(displacement between midpoints of planned and measured 70% isodose contours), were 0.48±0.40, -0.20±0.44 and 0.45±0.43mm along the Posterior-Anterior, Right-Left and Superior-Inferior directions, respectively, using acceptance criteria of 1mm-1°, and 0.72±0.18, 0.12±0.18 and -0.14±0.34mm, respectively, using acceptance criteria, 0.4mm-0.4°. Positional errors of the 80% isodose line were -0.36±0.43, 0.38±0.38, and 0.03±0.44mm, on the Posterior, Right, and Inferior edges of each profile, respectively, and 0.68 ±0.40, -0.14 ±0.38, and 0.88±0.40mm for the Anterior, Left, and Superior edges, respectively for the 1mm-1° criteria. Using the 0.4mm-0.4° criteria, errors were -0.35±0.23, 0.31± 0.18, and 0.72±0.27mm on the Posterior, Left and Inferior portion of each profile respectively and 1.12±0.18, 0.22±0.23, and 0.35±0.33mm for the Anterior, Left and Superior portions, respectively. Data ranged approximately two standard deviations about the mean. Winston-Lutz tests with errors of approximately 0.5mm correlated with increased Anterior error in three measurement sessions. Conclusions: The ExacTrac system is capable of achieving sub-mm(2Ï) accuracy given the alignment errors were small(<0.3mm) when Winston-Lutz results were small(<0.2mm), indicating pre-treatment corrections could be made.

Significance: Photon activated Auger electron therapy utilizes a keV-ranged, monoenergetic x-ray beam, and radiobiological and animal experiments studying this therapy require accurate dosimetry techniques. However, there exist few dosimetry protocols for low-energy x-ray beams. This research intended to use the CAMD synchrotron as a source of monochromatic, 35-keV x-rays and test dosimetry techniques of film and ion chamber. The hypothesis of my research was that depth-dose measured in a PMMA phantom using an air-equivalent ionization chamber and radiochromic film dosimeters in a PMMA phantom irradiated by a 35-keV, monochromatic x-ray beam will agree to within 5% of each other and to within 5% of dose determined from fluence-scaled Monte Carlo dose simulations. Methods: The narrow beam produced on the CAMD tomography beamline (0.1×2.8 cm2) was effectively broadened (2.5×2.8 cm2) by vertically oscillating experimental apparatus. Beam energy selected by the monochromator was verified using a Compton scatterer and powder diffraction methods. Depth-dose in PMMA was measured by an air-equivalent ion chamber using a modified AAPMs TG-61 (100-300 kV) formalism and by Gafchromic EBT film using 125-kVp calibration curves. Depth-dose was also determined from scaling MCNP5 Monte Carlo output by fluence measured using a NaI detector. Results: The powder diffraction energy measurement agreed closest to the monochromators setting (mean = -0.1±0.3 keV). Depth-doses performed on 5 separate experimental dates showed that beam fluence did not accurately scale to synchrotron ring current between dates. Depth-dose measurements from ion chamber and film at 2 cm resulted in film-measured dose underestimating ion-chamber measured dose by an average of 5.0±2.1%. Fractional Monte Carlo depth-dose simulations agreed well with ion chamber and film measurements, with maximum disagreements of 3.9% at 9.0-cm depth and 0.9% at 8.25 cm, respectively. Fluence-scaled, Monte Carlo dose determination overestimated ion chamber-measured depth-dose by 6.4±0.8% and overestimated film-measured depth-dose by 9.1±0.7%. Conclusions: Results of this research were unable to prove or disprove the hypothesis regarding 5% agreement of ion chamber and film dose measurements. Results also proved the hypothesis false for achieving 5% agreement between either ion chamber-measured dose or film-measured dose and dose determined from fluence-scaled Monte Carlo simulations.

The gravitational wave detectors at the LIGO Observatories have achieved record sensitivity to gravitational-waves produced by astrophysical systems. The LIGO Scientific Collaboration has analyzed data taken in several science runs, searching for different signals. We describe a search for black holes with less than a solar mass in the LIGO data taken from February 22 to March 24, 2005. No gravitational waves were found, and an upper limit was set on the rate of mergers of such binary systems. This search, as well as other searches for binary systems, are affected by non-stationary noise. We describe the sophisticated pipeline that attempted to reduce the false trigger rate while maximizing the sensitivity to simulated signals. Details regarding this search and interpretation of this search are presented along with new strategies to increase the confidence in detection through signal based vetoes and better template waveforms.