Recent events have underscored the need for the United States government to provide streamlined emergency response procedures and subsequent dose estimations for personnel responding to incidents involving radioactive material. Indeed, the National Council on Radiation Protection and Measurements Report No. 138 (NCRP 2001) indicates that exposures received by first responders will be important for a number of reasons, including planning for the appropriate use of key personnel in an extended emergency situation. In response, the Department of Homeland Security has published Protective Action Guides (DHS 2006) to help minimize these exposures and associated risks. This research attempts to provide some additional radiological exposure knowledge so that an Incident Commander, with limited or no information, can make more informed decisions about evacuation, sheltering-in-place, relocation of the public, turn-back levels, defining radiation hazard boundaries, and in-field radiological dose assessments of the radiation workers, responders, and members of the public. A method to provide such insight begins with providing a model that describes the physics of radiation interactions, radiation source and geometry, collection of field measurements, and interpretation of the collected data. A Monte Carlo simulation of the model is performed so that calculated results can be compared to measured values. The results of this investigation indicate that measured organ absorbed doses inside a tissue equivalent phantom compared favorably to the derived organ absorbed doses measured by the Panasonic thermoluminescence dosimeters and with Monte Carlo ‘N’ Particle modeled results. Additionally, a Victoreen 450P pressurized ion chamber measured the integrated dose and these results compared well with the Panasonic right lateral TLD. This comparison indicates that the Victoreen 450P ionization chamber could potentially serve as an estimator of real-time effective dose and organ absorbed dose, if energy and angular dependence corrections could be taken into account. Finally, the data obtained in this investigation indicate that the MCNP model provided a reasonable method to determine organ absorbed dose and effective dose of a simulated Radiological Dispersal Device in an Inferior-Superior geometry with Na99mTcO4 as the source of radioactive material.

Thesis (M.S. in environmental science)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 4, 2010). "School of Earth and Environmental Science." Includes bibliographical references (p.59-67).

Thesis (Ph. D.)--Johns Hopkins University, 1914. / Vita. Reprinted from the Physical review, second series, vol. v, no. 3, March, 1915.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

<p> The Spin Asymmetries of the Nucleon Experiment (SANE) measured the proton spin structure function <i>g</i>₂ in a range of Bjorken <i>x,</i> 0.3 &lt; <i>x</i> &lt; 0.8, where extraction of the twist-3 matrix element <i>d</i>₂<i>^p</i> (an integral of <i>g</i>₂ weighted by <i>x</i>²) is most sensitive. The data was taken from <i>Q</i>² equal to 2.5 <i>GeV</i>² up to 6.5 GeV². In this polarized electron scattering off a polarized hydrogen target experiment, two double spin asymmetries, <i> A</i>&par; and <i>A</i>_&perp; were measured using the BETA (Big Electron Telescope Array) Detector. BETA consisted of a scintillator hodoscope, gas &Ccaron;erenkov counter, lucite hodoscope and a large lead glass electromagnetic calorimeter. With a unique open geometry, a threshold gas &Ccaron;erenkov detector allowed BETA to cleanly identify electrons for this inclusive experiment. A measurement of <i>d</i>₂<i>^p</i> is compared to lattice QCD calculations.</p>

Diamond has long been the material of interest for radiotherapy dosimetry due to its high sensitivity, radiation hardness and near tissue equivalency. However natural diamond detector has not become a popular choice because of variability among detectors, high cost and response dependence on dose rate. The recent success in synthesizing single crystal diamond has reignited the interest. Synthetic diamond is highly reproducible in purity and electrical properties, combined with small size, it is a suitable candidate for small field dosimetry. A newly available synthetic single crystal diamond detector is being studied to determine the basic dosimetric characteristic and applicability in small field dosimetry. A series of measurements were made in comparison with a 0.125c.c ionization chamber, and two diode detectors. Response of the diamond detector is independent on dose, dose rate and energy. The output factors of small fields determined by the diamond detector is lower than that of the diode detectors and higher than that of the ionization chamber which are known to over response and under response respectively. In percentage depth dose and beam profile measurements, the diamond detector performs similarly with the two diode detectors. It is found that the diamond detector is suitable for small field relative dosimetry. Further investigation is required to study the spatial resolution of the diamond detector in different measurement geometry and the suitability in determining percentage depth dose in the buildup region. / published_or_final_version / Diagnostic Radiology / Master / Master of Medical Sciences

No description available.

No description available.

Current dose photon calculation algorithms have shortcomings in calculating dose distributions accurately in complex, heterogeneous phantoms. In this work, using existing Monte Carlo (MC) algorithms, we implemented and validated a comprehensive MC treatment planning system (MCTPS). We compared MCTPS with the corrected pencil beam algorithm used in the commercial TPS, CadPlan (V2.7.3). The accuracy of dose distributions calculated by MCTPS was studied for six lung cancer patients in two modes: without correction for inhomogeneity (the clinically used method) and with the equivalent tissue air ratio (EgTAR) inhomogeneity correction switched on. Without the use of inhomogeneity corrections, absorbed dose estimated by CadPlan is in error by more than 10% in the planning target volume (PTV). With the EgTAR correction, good agreement was observed for the dose to the PTV, however, in regions close to an interface, where a significant density gradient occurs, the error is up to 10%. Dose errors in other organs were studied using differential dose volume histograms.

Monte Carlo (MC) dose calculations cannot accurately assess the dose delivered to the patient during radiotherapy unless the patient anatomy is well known. This thesis focuses on the conversion of patient computed tomography (CT) images into MC geometry files. Metal streaking artifacts and their effect on MC dose calculations are first studied. A correction algorithm is applied to artifact-corrupted images and dose errors due to density and tissue mis-assignment are quantified in a phantom and a patient study. The correction algorithm and MC dose calculations for various treatment beams are also investigated using phantoms with real hip prostheses. As a result of this study, we suggest that a metal artifact correction algorithm should be a part of any MC treatment planning. By means of MC simulations, scatter is proven to be a major cause of metal artifacts. The use of dual-energy CT (DECT) for a novel tissue segmentation scheme is thoroughly investigated. First, MC simulations are used to determine the optimal beam filtration for an accurate DECT material extraction. DECT is then tested on a CT scanner with a phantom and a good agreement in the extraction of two material properties, the relative electron density rho_e and the effective atomic number Z is found. Compared to the conventional tissue segmentation based on rho_e-differences, the novel tissue segmentation scheme uses differences in both rho_e and Z. The phantom study demonstrates that the novel method based on rho_e and Z information works well and makes MC dose calculations more accurate. This thesis demonstrates that DECT suppresses streaking artifacts from brachytherapy seeds. Brachytherapy MC dose / Les calculs de dose Monte Carlo (MC) ne peuvent précisément déterminer la dose délivrée au patient, à moins de bien connaître son anatomie. Cette thèse se concentre sur la conversion des images tomographiques du patient en fichier de géométrie Monte Carlo. Les artefacts métalliques et leur effet sur les calculs de dose MC sont étudiés. Un algorithme de correction est appliqué sur les images avec artefacts et les erreurs de dose dues au mauvais assignement des densités et tissus sont quantifiées dans un fantôme et une étude de patient. L'algorithme de correction est aussi testé sur des fantômes avec de réelles prothèses de hanches et l'effet de correction sur les calculs de dose MC est étudié. En tant que résultat de cette étude, nous suggérons qu'un algorithme de correction des artefacts métalliques soit intégré à tout plan de traitement MC. Par le biais de simulations MC, le diffusé est prouvé être une cause majeure des artefacts métalliques. L'utilisation d'un scanner double énergie pour une méthode novatrice de segmentation de tissu est minutieusement étudiée. Tout d'abord, les simulations MC sont utilisées pour déterminer la filtration optimale de faisceau pour une extraction précise du matériau en scanner double énergie. La méthode à double énergie est ensuite testée sur un scanner avec un fantôme et un bon accord dans l'extraction des propriétés des deux matériaux, la densité électronique relative rho_e et le nombre effectif atomique Z est trouvé. Comparé à la segmentation conventionnelle des tissus réalisée sur la base des différents rho_e, la méthode novatrice de segmentation de tissu utilise les diff