Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 83 for “"effective dose"”.
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Effective dose estimation for U.S. Army soldiers undergoing multiple computed tomography scans
… tomography (CT). CT delivers more radiation dose than other diagnostic scanning modalities. Trauma patients are at an increased risk of radiation induced cancer because of the cumulative dose effects from multiple scanning procedures. Current methods for estimating effective dose, the …
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Effective dose enhancement using gold as a radiation sensitizer: a Monte Carlo study
… is to dramatically increase the amount of effective dose received by the tumor without increasing the amount received by the surrounding healthy tissue. Several contrast materials have been explored for this application with iodine and gadolinium receiving generating significant interest. …
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Impact of acquisition protocol variations on effective dose and risk for CT head examinations
PURPOSE: To propose a method for estimating the effective lifetime risk of radiation-induced cancer from different brain CT scan protocols in both paediatrics and adults and to develop a prospective method for estimating the number of cancer cases for patients undergoing CT brain scans when using …
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AP pelvis x-ray imaging on a trolley: the impact of trolley design, mattress design and radiographer practices on image quality and radiation dose
… practice on image quality and radiation dose for AP pelvis imaging on a trolley in order to optimise this imaging examination. AP pelvis was chosen as the focus of this thesis due to the frequency of this examination on a trolley and the dose implication associated with it.Materials and …
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Tomosynthesis in pulmonary cystic fibrosis
… scoring system, and to determine the effective dose from chest tomosynthesis in children. In a prospective study starting in 2008 clinical chest radiography or computed tomography (CT) were supplemented with a tomosynthesis examination of the lungs. Tomosynthesis findings were …
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Radiation dose measurement and prediction for linear slit scanning radiography
This study describes dose measurements made for linear slit scanning radiography (LSSR) and a dose prediction model that was developed for LSSR. The measurement and calculation methods used for determining entrance dose and effective dose (E) in conventional X-ray imaging systems were verified for …
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Radiation exposure of human populations in villages in Russia and Belarus affected by fallout from the Chernobyl reactor
… prospective as well as retrospective absorbed dose estimates has also been evaluated by using the optically stimulated luminescence in ordinary household salt. The dosimetric potential of salt was investigated in the laboratory with the aim to use salt as a retrospective dosemeter. The salt …
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A generic biokinetic model for C-14 labelled compounds
… a biological half life of 40 days yielding an effective dose coefficient of 5.8×10-10 Sv Bq-1. This overestimates the dose of all radiocarbon compounds that have been studied. An improved model has been developed that includes and alimentary tract, a urinary bladder, CO2 model, and an "Other" …
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Design and testing of a novel neutron survey meter
… of an instrument which can estimate the effective dose of a neutron field, accounting for both direction and energy of the field. This work represents a novel, real-time, approach to workplace directional neutron dosimetry. A 6Li-loaded scintillator based detector system was developed. …
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Maximum hypothetical accident analysis for HEU to LEU fuel conversion at the University of Missouri Research Reactor
… accident (MHA) analysis. For the 10-minute dose to workers in containment, a committed effective dose equivalent (CEDE) to the thyroid from the radioiodines was 0.889 mrem. To calculate the total effective dose equivalent (TEDE), two different sets of derived air concentrations (DACs) were …
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Cone Beam Computed Tomography - radiation dose and image quality assessments
… reconstruction, image resolution and radiation dose. When new technology is introduced one must make sure that diagnostic accuracy is better or at least as good as the one it can be expected to replace. The CBCT brand tested was two versions of Accuitomo (Morita, Japan): 3D Accuitomo with an …
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In-situ gamma-ray mapping of environmental radioactivity at Ithemba Labs and associated risk assessment
… 2j2Th, and "^K, respectively. The absorbed and effective doses (from external gamma irradiation) that were calculated for the NORM radionuclides have the ranges 10.4 -27.2 nGy.h"1 and 12.8 - 33.4 /iSv.y"!r respectively. The average NORM activity concentration results (from February and July …
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CONE BEAM COMPUTED TOMOGRAPHY (CBCT) DOSIMETRY: MEASUREMENTS AND MONTE CARLO SIMULATIONS
… protocol for CBCT. Computed tomography dose index (CTDI), a standardized metric in conventional CT dosimetry, or direct organ dose measurements have been limitedly used in the CBCT dosimetry.</p> <p>This dissertation investigated the CBCT dosimetry from the CTDI method to the organ, …
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Active Magnetic Radiation Shielding For Long-Duration Human Spaceflight
… solar particle events. The chronic radiation dose due to galactic</p> <p>cosmic rays on a typical Mars mission is on the order of 1 Sv, and additional acute</p> <p>radiation dose from solar flares can reach over 4 Sv, which is a potentially lethal dose.</p> <p>Hence radiation protection is a …
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An evaluation of the natural radioactivity in the soils of Okahandja and Karibib, Namibia
… were used to calculate the absorbed dose rates and effective dose rates in air in the two towns. The average absorbed dose rate in air in Okahandja is 77.3 ± 18.0 nGy/hr while that in Karibib is 77.6 ± 10.9 nGy/hr. However, the resulting average effective dose rate in Okahandja and …
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Assessment of natural radioactivity in the soils of the Ohorongo Cement plant and the town of Otavi, Namibia
… were used to calculate the absorbed dose rates and the effective dose rates in air across the different geographical areas in the plant and town. The values of (4.3 ± 1.5) × 10−2 mSv/y and (4.0 ±1.5) × 10−2 mSv/y obtained respectively for the mean effective dose rates in the Cement …
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Establishing an evidence-base for erect pelvis radiography : positioning, radiation dose and image quality
… assessing radiographic positioning, radiation dose and image quality. Methods: The experimental work described in this thesis was conducted in three phases. Each phase has its own methods with the purpose of achieving a specific set of aims. Phase One was the evaluation of the postural effects …
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Improving Dose-Response Correlations For Locally Advanced Nsclc Patients Treated With Imrt Or Pspt
… patients remains below 28 months. Higher tumor dose has been found to increase survival but also a higher rate of radiation pneumonitis (RP) that affects breathing capability. In fear of such toxicity, less-aggressive treatment plans are often clinically preferred, leading to metastasis and …
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Radionuclide concentrations and radiation hazard assessment in the soil of Otjiwarongo, Namibia
… radiation hazard parameters such as absorbed dose rate, effective dose rate, radium equivalent activity (Raeq), and external radiation hazard index (Hex), were calculated from the activity concentrations of the radionuclides. The mean absorbed dose rates in the ten areas vary from 90.0 ± 13.7 …
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