Purpose: There are conflicting results from studies on whether the ventilation (V) scintigraphy can be safely omitted or replaced by a chest x-ray. These studies were based on planar ventilation perfusion (V/Q) scintigraphy. We evaluated the value of the V single photon emission computed tomography (SPECT) on the final conclusion drawn from a V/Q SPECT and the possible role of the chest x-ray as a surrogate for the V SPECT. Methods Raw data of V/Q SPECT images and chest x-ray acquired within 48 hours over 18 months period were retrieved, reprocessed and reviewed in batches. The V SPECT, Q SPECT and chest x-ray were reviewed separately and in combination. Data on the presence and character of defects and chest x-ray abnormalities were recorded. The V/Q SPECT images were interpreted using the criteria in the EANM guideline and the Q SPECT and chest x-ray images were interpreted using the PISAPED criteria. Agreement between the diagnosis on the V/Q SPECT review and the Q SPECT and chest x-ray review was analysed. Results 21.1% of the patients were classified as 'PE present’ on the V/Q SPECT review whereas 48.9% were classified as 'PE present’ on the Q SPECT and chest x-ray review. Only 5.4% of defects seen on V SPECT had matched chest x-ray lung field opacity. Conclusion Our study showed that the omission of a V SPECT led to a high rate of false positive diagnoses and that the ventilation scan cannot be replaced by a chest x-ray.

Includes bibliographical references / Objectives: To assess initial experience with the use of a new SPECT-CT in the evaluation of lesions. Methods: The folder number, radiopharmaceutical used and type of scan of patients examined with a new Siemens T6 SPECT-CT between 2 April and 31 December 2013 were retrieved. The number of 99m Tc -MDP bone scans was sufficient for a detailed analysis. The scans were re-processed and reported by the observer before he was given any clinical information. Whole body planar, whole body planar plus SPECT and whole body planar plus SPECT-CT images were assessed successively in three separate sessions at least two weeks apart. At each session, the certainties of detection, localisation, and categorisation of each lesion were recorded. Results: A total of 539 lesions were seen on the whole body, SPECT and CT images in 133 patients. The whole body images showed no lesions in three patients and 378 lesions in 130 patients, 117(31%) lesions in areas not covered by the SPECT. SPECT detected 122 additional lesions in 79 patients. Thirty-nine (12.2%) lesions were seen only on CT in 32 (24.1%) patients. F or the 261 lesions seen on the planar images in the SPECT FOV, lesion detection was definite in 233 (89.3%), localisation definite in 151(57.9%) and categorisation definite in 123 (47.1%) lesions. On the SPECT, definite lesion detection, localisation and categorisation were recorded respectively for 259 (99.2%), 228 (87.4%) and 176 (67.4%) of the 261 lesions. Lesion detection, localisation and categorisation certainties were definite for 100%, 99.1% and 94.7% of the SPECT-CT lesions respectively. Conclusion: Whole body planar scintigraphy is essential in lesion detection. SPECT markedly improves lesion detection and localisation and CT enhances lesion categorisation.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998. / Includes bibliographical references (p. 132-134). / The management of environmental programs affects a great variety of issues and involves several stakeholders with diverse, and often conflicting, concerns. Any methodology proposed for environmental decision making should, then, be capable of integrating technical and value-laden objectives in a framework which ensures process transparency. Furthermore, only a methodology simple and easy to implement can achieve public involvement at every level, and, with it, achieve a thoroughly informed decision. Classic decision making techniques have provided the tools to organize decision problems in a sound logical structure. Unfortunately, actual applications have shown that, when it comes to the practical quantification of stakeholder values, these tools may be too burdensome to apply. This is particularly so in cases where non-technical public is a fundamental part of the decision process. In this thesis, the focus is on a methodology developed to assess stakeholder preferences regarding a number of objectives of environmental restoration activities, such as the minimization of costs and the impact on human health and safety, and on its combination with the structural approach provided by classic methods. Stakeholder input is used to produce a first set of relative weights using the Analytic Hierarchy Process in combination with value trees. The set of preferences so obtained, as well as possible inconsistencies in their assessments, are discussed with the stakeholders to revise the weights and reduce inconsistency. The stakeholders always have the final word regarding the relative weights. The prioritization procedure is presented through a case study. Insights gained from this real life application are also presented. / by Roberto Accorsi. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1997. / Includes bibliographical references (leaves 66-69). / Cancer remains a major medical problem accounting for over 500,000 deaths in the US annually. A common feature of most human tumors is their ability to induce the proliferation of new blood vessels, i.e. angiogenesis. Considerable evidence now exists which demonstrates that these tumor vessels are associated with a distinct range of morphological and physiological properties which are not present in normal tissue vasculature. Several studies now document that in a wide variety of tumor models, average tumor vessels have diameters two times those of normal tissue vessels. NMR techniques based on magnetic susceptibility mechanisms are sensitive to varying sizes of blood vessels. By using gradient echo (GE) and spin echo (SE) pulse sequences and different concentrations of an exogenous contrast agent, it is possible to determine the signal contribution from small versus large vessels by examining the change in T2 and T2* rates ([delta]R2 and [delta]R2*), i.e. the ratio of [delta]R2* to [delta]R2 increases with vessel size. This ratio provides an index for the average size of vessels within a voxel. The central goal of this research was to utilize such a tool in order to obtain a regional picture of the tumor vascular bed. Rats, inoculated with C6 glial cells, underwent an MR imaging series nineteen days after implantation, which comprised conventional SE and GE images prior to and following serial injections of an equilibrium iron oxide contrast agent (MION). Regions within the tumor and in the contralateral normal gray matter were identified. The change in the T2 rate and T2* rate ([delta]R2 and [delta]R2*) were calculated for each region. Since susceptibility contrast mechanisms designed to study the distribution of vessel sizes rely entirely on the compartmentalization of the contrast agent within the vasculature, the first set of experiments was designed to demonstrate the stability of MION to remain within the vasculature, despite the disruption in the blood brain barrier. The second experiments measured [delta]R2 and [delta]R2* as a function of contrast agent concentration and TE. The MR measurements were compared with predicted values of [delta]R2 and [delta]R2* made from histological assessment of vessel sizes and theoretical Monte Carlo simulation results. The steady state measurements of [delta]R2 and [delta]R2* in the first experiments demonstrated that once the maximum contrast agent concentration had been reached, the values of [delta]R2 and [delta]R2* remained stable over 90 minutes, suggesting that MION remains within the vasculature. In the second experiments, significant differences were observed between the tumor and contralateral deep gray matter. Specifically, the ratio of ([delta] R2*/ ([delta]R2 was greater in the tumor than the normal brain, by a factor of 1.9 ± 0.2. From histologic sections and numerical simulations, the corresponding ratio was predicted to be 1.9 ± 0.1. These ratios are suggestive of a greater relative density of large vs small vessels. Maps of the ratio [delta]R2*/[delta]R2 were also produced on a pixel by pixel basis. Regions of high intensity on these maps (indicating a higher ratio of [delta]R2*/[delta]R2) corresponded well with the location of the tumor as determined using conventional images. / by Joëlle Dennie. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1997. / Includes bibliographical references (p. 75). / The photonuclear production of radioisotopes using electron LINAC bremsstrahlung sources offers an industry alternative to reactor and ion beam production methods. One such method under development is the utilization of the Giant Dipole Resonance in the (y,n) reaction cross-section. This method is being studied for use in the production of 99mTc from enriched 100Mo by electron beam induced bremsstrahlung photons. Of primary concern to any radioisotope production system is the specific activity it is able to create of the radioisotope. In a photoneutronic production system maximizing the number of GDR photons on a given target increases the specific activity. Proper design and optimization of the electron-to-photon converter maximizes the number of GDR photons. This study examines some alternative types of converter design. MCNP is used to predict isotope yields and energy deposition in the converter assemblies and an Excel Spreadsheet is used to analyze the heat-transfer capabilities of the systems. Optimized designs are presented for the different types of converters studied. A radiantly cooled converter is presented as a low-yield design, while a circulating loop of molten lead is analyzed for use in a high-yield system. / by Jess L. Iverson. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998. / Includes bibliographical references (leaves 32-33). / NMR experiments implementing two-bit controlled-NOT logic gates on alanine (JAB = 35.1 Hz) and 2,3- dibromothiophene (JAB = 5.6 Hz) were performed. Spectra were collected at a variety of tip angles (angles between the spin and the axis of magnetization) by applying a selective RF pulse of constant power and variable duration. From this collection of spectra, the effective Hamiltonian of the spin system was derived and found to contain an internal Hamiltonian. In a spin system with weak coupling, the internal Hamiltonian contains spin-spin coupling terms. The effective Hamiltonian gives a more complete description than the currently used transition Hamiltonian. Understanding the dynamics of a spin system not only furthers the field of NMR but has application in the subject of quantum computing. NMR pulse sequences for four-, eight- and 16-spin controlled-NOT logic gates were developed. A pattern is evident and the pulse sequence for any number of spins can be derived. Disregarding the differences in the spin-spin coupling constants of different spin systems, these results suggest that the total time to implement a controlled-NOT logic gate in NMR does not increase exponentially with the number of spins in the system. / by aMy e dunlop. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998. / Includes bibliographical references (leaves 53-54). / In an effort to provide an accurate real-time continuous emissions monitor (CEM) for hazardous air-pollution metals as a viable option to EPA Method 29, a Microwave Induced Plasma (MIP) system is under development for real-time atomic emission spectroscopy in stack exhaust. This MIP-CEM has a nebulizer calibration subsystem attached to the sample line for real-time span calibration of the monitored metal concentrations. In order to quantify the amount of metal mass measured in the effluent flow, it is necessary to determine the analyte metal mass transport efficiency of the nebulizer system. A novel new approach to determine the nebulizer efficiency during plasma operation was tested in this thesis. A 0.1-mm tungsten filament attached to a 4- mm diameter alumina rod was used to introduce a known amount of mass into a nitrogen plasma at 0.5-cfm sample line flow in 6 different positions relative to the end of the sample line. The tungsten filament was heated by plasma radiation. These signals, obtained from the direct rod insertions, were then correlated to masses of metals aspirated by the nebulizer and drawn into the plasma through a quartz "T". The mass transport efficiency as a function of rod insertion position was calculated by dividing the correlated mass by the total mass aspirated by the nebulizer to achieve an identical signal. In the 4- inch long drift distance between the end of the sample line and the plasma sustaining waveguide, measurements from 0.5 inches away from the end of the sample line to 1.75 inches away, in 0.25-inch increments, were repeated, and the results tabulated. The efficiencies generally decreased as the rod was inserted closer to the plasma, with the efficiency extrapolated to 0.644 ± 0.153 % at the end of the sample line. The extrapolated value is in fair agreement with the efficiency used in the most recent field test conducted at Research Triangle Park in Raleigh-Durham, North Carolina. Initial tests at one insertion location of 1.75 in. were also done for a different nitrogen flow of 1.0 cfm and for air at 0.5 cfm. These initial tests are inconclusive, and more measurements are needed. Also, further testing is warranted for the determination of other factors, such as moisture, and the impact on the efficiency. / by Guadalupe Jorge Flores III. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1998. / Includes bibliographical references (p. 193-198). / The purpose of this research was to use state-of-the-art nuclear and fuel performance design packages to develop extended cycle cores for existing Light Water Reactor (LWR) designs which respect current fuel burnup limits while considering the full range of practical design and economic considerations. The driving force behind this research was the desire to make nuclear power more economically competitive with fossil fuel options by permitting higher plant capacity factors. In this thesis, reference cores for a 38.8 Effective Full Power Month (EFPM) PWR cycle and a 45 EFPM BWR cycle were developed and evaluated. To achieve these cycle lengths the designs use a single batch reloading strategy and contain fuel with enrichments as high as 7.4W/0 U2 3 5 (exceeding the current licensing limit of 5W/). The PWR design uses gadolinium oxide (Gd20 3) and IFBA (Integral Fuel Burnable Absorbers - a thin fuel pellet surface coating of ZrB2) as burnable poisons to hold down excess reactivity and to control power peaking. The BWR employs only Gd203. Both core designs require higher worth control rods in order to meet shutdown safety requirements. Fuel performance issues were also investigated. The presence of high burnup fuel assemblies in areas of greater-than core-average power leads to fuel performance concerns which must be carefully addressed. The effects of waterside corrosion, increased fission gas pressure, and intensified cladding strain in these assemblies must be carefully quantified. Steady state-analyses of fuel pin internal pressure performed on the PWR design show acceptable fuel pin performance. Fuel performance areas requiring further research were highlighted. Economic calculations show that extended cycle, single batch loaded cores have a fuel cost that is $13 million to $17 million per year more expensive than an optimized multi-batch strategy. This deficit would have to be made up from the net benefits of a higher capacity factor (e.g., less replacement energy, fewer refueling outages) levelized over plant lifetime. / by Michael Vincent McMahon. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1997. / Includes bibliographical references (leaves 52-54). / A model has been developed to predict the pressure generation and concentrations of oxygen and hydrogen gas in a Multi-Canister Overpack (MCO) containing metallic uranium N Reactor fuel during staging, drying, conditioning, and storage at the Hanford Site. Ass0ciated uncertainties with each parameter were also calculated. The mechanisms that were included in the analysis were: -- Uranium Corrosion in which oxygen is consumed, or water is consumed and hydrogen is produced, -- Uranium Hydriding in which hydrogen is consumed, and -- Radiolysis in which water is consumed and hydrogen and oxygen are produced. The model characterizes the evolution of gases inside the MCO for the three ,egimes in which the fuel will be staged or stored. Prior to treatment the fuel will be immersed in water in the MCO. Proceeding the first treatment step, the MCO will contain no free water, but water vapor will contribute to a moist atmosphere. After the last treatment step, the inside of the MCO will be dry with only tightly-bound chemisorbed water remaining associated with sludge that will be present with the fuel. The model shows that for likely conditions inside the MCO, the container will not pressurize during its expected service life. The model also shows the effects that varying parameters have on the final pressure. / by Lisa Stiles Shell. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1997. / Includes bibliographical references (p. 329-338). / Two complementary approaches were used to characterize transport on the Alcator C­Mod tokamak. The first was an empirical analysis of the scaling of transport with P*, the ion Larmor radius normalized to the plasma size. The second was a comparison of the transport predictions from the IFS-PPPL model of ion temperature gradient (ITG) driven turbulence to observations on C-Mod. The P* scaling experiments on C-Mod extend the range of plasma parameters over which the dimensionless scaling approach has been tested in both magnetic field ( to 8 T) and density (to (ne ) = 3.8 x 1020 /m3) ... / by Jeffrey Marc Schachter. / Ph.D.