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Wang, Na. "Estimation of Extra Risk and Benchmark Dose in Dose Response Models." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/WangN2008.pdf.
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Zeidan, Mohammad. "Assessment of Mean Glandular Dose in Mammography." Thesis, University of Canterbury. Department of Physics, 2009. http://hdl.handle.net/10092/2653.
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The mean glandular dose (MGD) was measured for a breast phantom by using molybdenum/molybdenum and molybdenum/rhodium target/filter combinations, at different kVp 26, 28 and 32 kilovolts. The phantom thickness was 7.5cm and was made of BR12 material. The change of dose was studied as a function of depth inside the phantom at different depths from the surface, namely 3.3, 4.3 and 5.3cm, by using TLDs. It was found that the MGD value for different combinations of beam quality (HVL) and energy (kVp) did not exceed the recommended values given by different protocols. The Mo/Rh target/filter required lower doses to achieve the same or better results compared with the Mo/Mo target/filter. The change in the surface dose as a function of kVp was more significant for Mo/Rh than for the Mo/Mo. Studying the change in dose within the breast, as a function of depth gives a better understanding of the interactions between radiation and tissue inside the breast. It should be noted that the MGD is a tool for optimization of the mammography parameters. However, the MGD should not be used directly to estimate the risk of determinable health effects from mammography. This will ultimately help to determine limits for the breast surface dose and a better understanding of cancer risk. In future work, we will try to measure the change of the dose as a function of depth by using more kVp, HVL, different breast composition and different target/filter combinations to give a wider picture for different situations.
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Tootell, A. K. "Radiation dose assessment : measurement, estimation and interpretation." Thesis, University of Salford, 2018. http://usir.salford.ac.uk/48041/.
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New technologies or methods of image acquisition are driven by the need for increased anatomical information to improve diagnostic accuracy or surgical planning. These new technologies are often accompanied with additional radiation dose yet this can be justified through the consideration of the benefit it brings. Examples include the use of CT colonography instead of double contrast barium enemas, CT urography replacing intravenous urography and, in nuclear medicine imaging the increased use of CT imaging as part of single photon emission tomography and positron emission tomography to correct emission data or localise or characterise identified lesions. Manufacturers are quick to promote their systems as “low-dose” but little independent evaluation of this claim existed. In the context of nuclear medicine, the additional imaging raised questions as to the use of the attenuation correction data specifically. The question of should the cross sectional images be reviewed for pathology was has been the focus of debate. It was recognised that the quality of these images is poor due to the “low-dose” acquisition. The research presented in this thesis and portfolio of published work aimed to establish an accurate method of assessing the radiation dose, initially from the CT attenuation correction acquisition, but later in other imaging modalities. In this thesis eight papers are used to illustrate the methods developed in this work, and how they were applied to other fields of medical imaging. Six of these papers were completed as the first author and the remainder as co-author. Initially, the concepts of radiation dose were critically evaluated. Following identification of sub-optimal techniques, steps were taken to improve the accuracy of dose measurement using thermoluminescent dosimeters, digital dosimeters and simulation through software. These techniques have been analysed critically and where appropriate improvements are recommended. Radiation dose, in particular the associated risk, is a challenging concept to convey to patients and care givers and simply providing a figure of dose does not convey the required information needed to allow consent to be given. Methods by which radiation dose and risk can be interpreted is critiqued with reference to published literature. The thesis concludes with a description of the intellectual contribution illustrating the role played as first author and as a co-author in the works included in the portfolio and a review of impact considering citation metrics and downloads. It was also decided to include citations from within the Diagnostic Imaging Research Programme and PhD theses from The University of Salford to demonstrate how research activities within the portfolio of published works have influenced other methodologies and outputs.
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Prokopčiuk, Nina. "Application of probabilistic methods for ionizing radiation dose assessment." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20111201_142318-45933.
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The aim of this doctoral dissertation is to assess the probable impact of ionizing radiation on the public health and the environment (including fauna and flora) in the vicinity of nuclear power engineering objects (in case of the Maišiagala near-surface radioactive waste repository – by evaluating the possible impact on the human health, while in case of the Ignalina NPP cooling basin, Lake Drūkšiai – by evaluating the possible impact on the freshwater ecosystem biota) by applying probabilistic methods as well as to determine whether this activity after assessment of its character and impact on the environment meets the standards valid in the Republic of Lithuania or in the European Union and is permissible at a selected site at present or in the future.
In the work two main programs, RESRAD-OFFSITE and ERICA, using scattering of site-specific parameter values and probabilistic (correlation, regressive, sensitivity, etc.) analysis, have been applied.
It has been determined that in the environment of the Maišiagala repository after installation of additional protective barriers the annual effective human exposure dose is significantly lower as compared to the limited dose and 95th percentile dose not exceed the exposure of 1 mSv per year regulated in the hygiene standards.
The exposure dose rate of standardized organisms of Lake Drūkšiai, the Ignalina NPP cooler, freshwater ecosystem biota due to the INPP discharges and waterway radionuclide migration from a hypothetic... [to full text]Šios daktaro disertacijos tikslas - įvertinti galimą jonizuojančiosios spinduliuotės poveikį visuomenės sveikatai ir aplinkai (tame tarpe gyvūnijai ir augalijai) branduolinės energetikos objektų aplinkoje (Maišiagalos radioaktyviųjų atliekų saugyklos atveju - vertinant galimą poveikį žmogui, ir IAE aušintuvo Drūkšių ežero atveju - vertinant galimą poveikį gėlavandenės ekosistemos biotai), taikant tikimybinius metodus; nustatyti, ar ši veikla, įvertinus jos pobūdi ir poveikį aplinkai, atitinka Lietuvos Respublikoje arba Europos Sąjungoje galiojančius standartus, yra leistina pasirinktoje vietoje dabartiniu laikotarpiu arba ateityje. Darbe buvo taikomos 2 pagrindinės programos: RESRAD-OFFSITE ir ERICA., naudojant vietines sąlygas atitinkančius parametrų verčių išbarstymą, taikant tikimybinę (koreliacinę, regresinę, jautrio ir kt.) analizę. Nustatyta, kad, įrengus papildomus apsauginius barjerus, Maišiagalos saugyklos aplinkoje metinė efektinė gyventojų apšvitos dozė yra ženkliai mažesnė lyginant su apribotosios dozės dydžiu, 95 procentilė nesiekia higienos normose patvirtintos 1mSv per metus ribinės dozės dydžio. Ignalinos AE aušintuvo Drūkšių ežero gėlavandenės ekosistemos biotos standartizuotųjų organizmų apšvitos dozės galia dėl IAE nuotekų ir radionuklidų sklaidos vandens keliu iš hipotetinio Stabatiškės radioaktyviųjų atliekų kapinyno rodo, kad apšvitos dozės galia dėl antropogeninės kilmės radionuklidų jonizuojančiosios spinduliuotės poveikio neviršija Europos Sąjungoje... [toliau žr. visą tekstą]
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Cezeaux, Jason Roderick. "Determination of petroleum pipe scale solubility in simulated lung fluid." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2271.
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Naturally occurring radioactive material (NORM) exists in connate waters and, under the right conditions during oil drilling, can plate out on the interior surfaces of oil and gas industry equipment. Once deposited, this material is commonly referred to as ??scale.?? This thesis is concerned with the presence of 226Ra in scale deposited on the inner surfaces of oil drilling pipes and the internal dose consequences of inhalation of that scale once released. In the process of normal operation, barium sulfate scale with a radium component adheres to the inside of downhole tubulars in oil fields. When crude flow is diminished below acceptable operational requirements, the pipe is sent to a descaling operation to be cleaned, most likely by a method known as rattling. The rattling process generates dust. This research investigated the chemical composition of that aerosol and measured the solubility of pipe scale from three oilfield formations.
Using standard in-vitro dissolution experimental equipment and methods, pipe scale is introduced into simulated lung fluid over a two-week period. These samples are analyzed using quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), known for very low detection limits. Analysis reveals virtually no 226Ra present in the lung fluid exposed to pipe scale. Sample measurements were compared against background measurements using Student??s t test, which revealed that nearly all the samples were statistically insignificant in comparison to the lung fluid blanks. This statistical test proves within a 95% confidence interval that there is no 226Ra present in the lung fluid samples. These results indicate that inhaled NORM pipe scale should be classified as Class S and serve to further confirm the extreme insolubility of petroleum pipe scale.
For dose calculations, the S classification means that the lung is the main organ of concern. Radium-226 from petroleum pipe scale does not solubilize in the interstitial lung fluid, and does not, therefore, enter the bloodstream via respiratory pathways. Since there is no removal by dissolution, the 500 day biological half-life implied by the S classification is based solely on the mechanical transport of 226Ra out of the lungs by phagocytosis or the mucociliary escalator.
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Oetzel, Alysh. "DOSE RELEVANCE IN DYNAMIC ASSESSMENT AND SUBSEQUENT LANGUAGE INTERVENTIONS OF BILINGUAL POPULATIONS DELIVERED THROUGH TELETHERPAY." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2852.
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In 2007, it was estimated that approximately 20% of the United States population spoke more than one language (Grosjean, 2012). As this statistic continues to rise, it is imperative that speech-language pathologists (SLP) are prepared to serve a linguistically inclusive caseload. Dynamic assessment (DA) allows clinicians to assess bilingual children while avoiding sources of bias that are often associated with norm-referenced testing. Utilizing DA to evaluate the multifaceted skills associated with narrative language can provide clinician’s clinical direction for intervention planning (Douglas, Chanthongthip, Ukrainetz, Spencer, and Steeve, 2017). DA is often structured as a pretest-teach-posttest model, which provides insight on current learning ability rather than current skillset. Dose refers to both the measured quantity of a therapeutic agent to be taken at one time and the specification of on-going exposure to an again (i.e., daily, weekly, monthly, etc) (Justice, 2018). In reference to speech-language pathology, dose often refers to the duration of intervention sessions over a given period. However, researchers are beginning to conceptualize dose as the engagement in therapeutic events rather than the duration of time spent in a session (Williams, 2012). In such cases, dose is represented as something the child does (e.g., produces a target phoneme) and as something the clinician does (e.g., providing exposure to a target phoneme) (Hassink & Leonard, 2010). While research on dose continues to develop, there is little research on implications of dose in bilingual populations. Due to the current COVID-19 global pandemic, many SLPs have transitioned their practice to alternative methods of delivery. The current study aims to examine the impact and opinions of practicing SLPs on dose, narrative intervention, and dynamic assessment of bilingual populations. The study surveyed licensed SLPs to obtain information on the current practices and definitions of dose, DA, and subsequent language interventions to bilingual populations.
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Kim, Kwang Pyo. "Inhalation dose assessment risk assessment of airborne particulates to workers in the Florida phosphate industry /." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013056.
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Obeid, Muhammad Hassan. "Assessment of Low-Dose Radiotoxicity in Microorganisms and Higher Organisms." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-194470.
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This work was dedicated to quantify and distinguish the radio- and chemitoxic effects of environmentally relevant low doses of uranium on the metabolism of microorganisms and multicellular organisms by a modern and highly sensitive microcalorimetry. In such low-dose regime, lethality is low or absent. Therefore, quantitative assays based on survival curves cannot be employed, particularly for multicellular organisms. Even in the case of microbial growth, where individual cells may be killed by particle radiation, classical toxicity assessments based on colony counting are not only extremely time-consuming but also highly error-prone.
Therefore, measuring the metabolic activity of the organism under such kinds of conditions would give an extremely valuable quantitative measure of viability that is based on life cell monitoring, rather than determining lethality at higher doses and extrapolating it to the low dose regime. The basic concept is simple as it relies on the metabolic heat produced by an organism during development, growth or replication as an inevitable byproduct of all biochemical processes. A metabolic effect in this concept is defined as a change in heat production over time in the presence of a stressor, such as a heavy metal. This approach appeared to be particular versatile for the low dose regime. Thus, the thesis attempted in this case to measure the enthalpy production of a bacterial population as a whole to derive novel toxicity concepts.
In the following chapters, an introduction about the properties of ionizing radiation will be briefly presented, in addition to a review about the isothermal calorimetry and its application in studying the bacterial growth. Later in chapter 2, the effect of uranium on the metabolic activity of three different bacterial strains isolated form a uranium mining waste pile together with a reference strain that is genetically related to them will be investigated. Due to the lack of published dedicated calibration techniques for the interpretation of heat production of bacterial cells under the conditions of calorimetric recordings, additional experiments, thorough investigations of the effects of experimental conditions, have been carried out in order to guide the interpretation of calorimetric results.
In chapter 3, the differentiation between chemi- and radiotoxicity of uranium has been addressed by isotope exchange, which was a key effort in this thesis as it opens new experimental approaches in radioecology. In chapter 4, through investigating the role of the tripeptide glutathione (GSH) in detoxifying uranium, it will be shown to which degree the intrinsically unspecific signal provided by metabolic heat can be related to highly specific metabolic pathways of an organism, when combined with genetic engineering. The demonstration of gaining molecule-specific information by life metabolic monitoring was another experimental challenge of this thesis and provides proof of principle that can be extended to many organisms.
Finally in chapter 5, an attempt has been undertaken to establish a minimal food chain, in order to study the effects of the exposure of a multicellular organism to uranium through its diet.
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Xiong, Hui. "Nonparametric Statistical Approaches for Benchmark Dose Estimation in Quantitative Risk Assessment." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202699.
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A major component of quantitative risk assessment involves dose-response modeling. Therein, an appropriate statistical model that approximately quantifies the relationship between exposure level (dose) and response (adverse endpoint) is fit to experimental data. The objective of this dissertation is to estimate adverse risks encountered in settings when the statistical model is formally defined and developed. From this, statistical inferences on the risk are conducted.First introduced are eight parametric models. The advantage of parametric models is they can produce consistent result when the selected model fits the dose-response curve very well. The simplicity of knowing the expression of these models allows for the construction of a variety of lower confidence limits, based on the Wald approach.However, if the true dose-response curve deviates significantly from a posited parametric model, the result may perform poorly. Non-parametric methods are then needed. The percentile bootstrap method from linear splines with Pool Adjacent Violator is first introduced. The method appeals to an asymptotic approximation, hence there is interest in assessing the small-sample coverage properties of this method. These are addressed via Monte Carlo computer simulations. We find that this method with four doses operates reasonably well at large sample sizes except for the concave increasing dose-response curve. In practice, small sample sizes are more common, therefore we turn to increasing the number of doses. We do see that, in general, the coverage becomes better as the doses number increases.To study the most common four dose design, the biased-corrected and accelerated bootstrap method from linear spline with Pool Adjacent Violator and discrete delta approach are also introduced. Simulation results show that the coverage are similar from these methods and have no improvement over the concave increasing dose-response curve.A final quadratic spline is then considered. For four doses design, this is repeated at four different points, to find an averaged extra risk function. In order to understand the operating characteristics of the method, another Monte Carlo simulation study is undertaken. This study produces similar results to those found using the percentile bootstrap method from linear splines.
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Sand, Salomon. "Dose-response modeling : evaluation, application, and development of procedures for benchmark dose analysis in health risk assessment of chemical substances /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-420-1/.
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Bueno, Vizcarra Marta. "Absorbed dose assessment in the presence of tissue heterogeneities in external radiotherapy." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/134363.
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The absorbed dose assessment in the presence of tissue heterogeneities in external radiotherapy is an issue that has concerned the medical physics community for almost three decades and it is still a matter of concern. Aiming to obtain dose distributions in clinically-acceptable computation times, analytical dose calculation algorithms integrated in treatment planning systems based their calculations on water-equivalent properties and elemental compositions of each material are disregarded despite the fact that radiation interaction processes strongly depend on them. This approximation provides reasonable accuracy in water-like tissues but the reliability of predicted dose distributions in the patient might be questioned when the radiation beam is traversing complex density heterogeneities, such as air, lung or bone. Experimental verification of dose calculation algorithms is essential and ionization chambers (IC) are the reference detectors for this purpose. However, correction factors to determine the absorbed dose in materials other than water are unknown for most IC types and therefore, they cannot procure reliable measurements in heterogeneous media. Monte Carlo (MC) simulations offer a high precision in dose calculation by tracking all particles individually taking into account the specific properties of each material. Unfortunately, accuracy and computation speed are inversely proportional and MC-based approaches generally entail long calculation times, unaffordable in the clinical routine. Nevertheless, for the cases where the expected errors in the predicted dose distributions during treatment planning are significant, i.e. when the radiation beam path is highly inhomogeneous, the benefit of resorting to MC dose calculations to achieve higher accuracy would be undoubtedly worth a presumably long computation time.
In this thesis the suitability of several detectors to accurately determine the absorbed dose in the presence of high-density heterogeneities was evaluated. Ultra-thin thermoluminescent detectors (TLDs) and radiochromic films were considered as potential candidates for entailing low perturbation effects. MC dose calculations enabled to validate and understand the experimental results. Further, both dosimetric techniques were employed to thoroughly examine the behavior of a recently-released non-analytical dose calculation algorithm (AXB)¿which copes with the elemental composition of materials and thus, is claimed to yield promising results¿in heterogeneous phantoms. Finally, a fast algorithm named the heterogeneity index (HI) was developed to quantify the level of patient tissue heterogeneities traversed by the radiotherapy beam. The validity of this HI to easily predict the accuracy of dose distributions based on analytical dose calculations was analyzed by evaluating the correlation between the HI and the dose uncertainties estimated by using MC as the reference.
The results show that a detector of 50µm thickness can provide reliable absorbed dose measurements in high-density heterogeneities since perturbation correction factors are unneeded. AXB was found to provide comparable accuracy to MC dose calculations in the presence of heterogeneities but uncertainties in the material assignment procedure might lead to significant changes in the dose distributions, which deserves a word of caution when carrying out experimental verifications. Finally, HI was found to be a fast and good indicator for the accuracy of dose delivery in terms of tumor dose coverage. Accordingly, HI can be implemented in the clinical routine to decide whether or not a MC dose recalculation of the plan should be considered to ensure that dose uncertainties are kept within tolerance levels. In conclusion, this thesis work tackled the main concerns on the absorbed dose calculation and measurement in the presence of tissue heterogeneities.
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Leidel, Jason M. "In vitro partial-body dose assessment using a radiation responsive protein biomarker /." Download the thesis in PDF, 2005. http://www.lrc.usuhs.mil/dissertations/pdf/Leidel2005.pdf.
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Osei, Ernest Kwaku. "Assessment of fetal radiation dose to patients and staff in diagnostic radiology." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323356.
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Jorge, Carlos Alexandre Fructuoso. "Received radiation dose assessment for nuclear plants personnel by video-based surveillance." Instituto de Engenharia Nuclear, 2015. http://carpedien.ien.gov.br:8080/handle/ien/1463.
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This work proposes the development of a system to evaluate received radiation dose for nuclear plants personnel. The system is conceived to operate in a complementary form to the existing approaches for radiological protection, thus o ering redundancy, what is desirable for critical plants operation. The proposed system must operate in an independent form on the actions to be performed by the operators under evaluation. Therefore, it was decided it would be based on methods used for video surveillance. The nuclear plant used as example is Argonauta Nuclear Research Reactor, belonging to Instituto de Engenharia Nuclear, Comiss~ao Nacional de Energia Nuclear (Nuclear Engineering Institute, National Nuclear Energy Commission). During this thesis research, both radiation dose rate distribution and video databases were obtained. Methods available in the literature, for targets detection and/or tracking, were evaluated for this database. From these results, a new system was proposed, with the purpose of meeting the requisites for this particular application. Given the tracked positions of each worker, the radiation dose received by each one during tasks execution is estimated, and may serve as part of a decision support system.
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Clark, Haley. "Assessment of spatially inhomogeneous intra-organ radiation dose response in salivary glands." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61113.
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Oertli, David Bernhardt. "Proton dose assessment to the human eye using Monte Carlo n-particle transport code (MCNPX)." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1024.
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Piqueras, Pardellans Joaquim. "Assessment of a micro-grid Ionization-chamber (EOS) for low-dose chest radiography." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/378369.
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EOS és una nova tecnologia d'imatge que fa servir un detector de radiació gasós, una cambra d'ionització de micro-reixeta, derivada del Micromegas desenvolupat per Georges Charpak (Premi Nobel 1992) per recerca en física d'altes energies al CERN (Ginebra, CH). Aquests detectors poden obtenir imatges mèdiques a baixa dosi, permetent col·limacions estrictes que eviten la radiació difusa que degrada dosi i qualitat. El prototip EOS, fent servir feixos de raigs-X molt fins (500 µm), va ser pensat per fer radiografia a baixa dosi de l'esquelet en bipedestació. Dissenyat amb dos tubs de raigs-X i dos detectors, realitza una adquisició per escanejat lineal biplanar sincrònica, de dues imatges (a 90º) del cos. Aquest mètode biplanar permet l'extracció automàtica de punts de referència anatòmics que poden ser matemàticament projectats com un model 3D de l'esquelet real del pacient. El programari EOS pot generar models 3D amb baixa dosi, entre 1/10 i 1/100, de les modalitats existents (radiografia computada (CR), radiografia digital (DR), o TC a baixa-dosi). L'objectiu principal de la recerca d'aquest prototip, la imatge de columna, va ser validat, i el seu subseqüent re-disseny industrial ha acabat com un dispositiu mèdic certificat per a estudis de l'esquelet: EOS ('EOS Imaging, Paris, France)'.
Preparant la fase experimental de EOS en columna, un segon objectiu va ser considerat: valorar l'aplicabilitat del prototip EOS a l'exploració radiogràfica més freqüent: radiografia de tòrax. Si EOS fos validat, permetria aplicar-lo a un altre camp del radiodiagnòstic. La radiografia del tòrax és una prova que pot comportar algunes dificultats en un dispositiu voluminós, d'escanejat lineal, biplanar, amb baixa dosi i baixa resolució espacial, com són els detectors de micro-reixeta, a investigar.
Material i mètodes: Es va preparar un estudi prospectiu comparant exploracions repetides entre EOS i un equip radiogràfic estat-de-l'art (DR, detector pla de aSi-Csi), per valorar l'aplicabilitat clínica, problemes tècnics, dosi i qualitat d'imatge. Un grup de 40 adults, amb radiografia de tòrax programada al Hôpital Univ. Erasme (Brussel·les, BE), van ser enrolats per a fer un estudi repetit amb EOS (amb 50% dosi de CR). Les imatges recollides van ser puntuades independentment per quatre radiòlegs seguint els 'European quality criteria in diagnostic imaging', incorporant reptes com valorar estructures anatòmiques fines. Es recolliren dades tècniques, estudis dosimètrics addicionals, comparatius amb CR, i mesura de dades de dosi i de rendiment del detector.
Resultats: 37 dels 40 casos van ser analitzats. La radiografia va ser correcta amb EOS, amb 13,5% d'estudis repetits. La dosi de radiació es superior amb EOS (0.22 mGy) que amb DR (0.05) però menys que la DRL o dosi per CR. Artefactes de soroll i 'arrissat' redueixen la FTM (funció de transferència de la modulació) mesurada a 1-1.5 pl/mm. La puntuació en qualitat d'imatge entre EOS i DR va ser comparable, amb millor puntuació per a EOS en via aèria, mediastí o en cobertura anatòmica.
Conclusió: EOS és una modalitat funcional que compleix les dosis de referència. La dosi és més alta que per DR i més baixa que per CR, per supressió de la radiació difusa. En qualitat d'imatge, EOS no mostra valoracions inferiors significants a la DR, fins i tot en estructures fines; pot atribuir-se a la resolució més gran de densitats i a l'absència de difusa que compensen la seva inferior resolució espacial. Caldrà fer desenvolupaments addicionals per millorar el control de la dosi i per millorar resolució, i caldrà fer recerca dirigida a validar resultats en sèries amb patologies clíniques.The EOS is a new 2D/3D radio-imaging technology that uses a gaseous radiation detector and micro-grid ionization chamber derived from Micromegas, the micro-grid developed by the Nobel Prize winner Georges Charpak and extensively used in high-energy research (eg, CERN, Geneva, Switzerland). The detectors are very efficient and enable low-dose medical imaging by stringent collimation, which avoids the undesired scattered radiation that increases dose and degrades image quality. The EOS prototype uses very thin (500 µm) fan-like x-ray beams and was planned for low-dose standing radiography of the human skeleton. It has two x-ray tubes and two detectors that allow synchronous biplanar linear acquisition of two 90-degree images of the body. The biplanar method was designed for automatic extraction of anatomic reference points that can be mathematically projected as a 3D model of a patient's skeleton. EOS software can build 3D models using lower radiation doses (1/10 to 1/100) than existing systems (computed radiography [CR], digital radiography [DR], or low-dose CT). The main application of the prototype, spine imaging, has been validated, and the subsequent, re-designed industrial EOS (EOS Imaging, Paris, France) has attained certification for skeletal studies. While preparing the experimental phase of EOS for spine imaging, a second objective was considered: to assess applicability of the EOS prototype to another field of imaging, the chest x-ray, the most common radiologic exam. Chest x-rays could pose several difficulties for a large, linear-scanning, biplanar, low-dose and low-spatial-resolution technique, in this case micro-grid detectors, which would have to be investigated. Material and methods: A prospective study was designed to assess the clinical feasibility, technical problems, dose and image quality of EOS as compared to a state-of-the-art DR system, the aSi-CsI flat panel detector. Forty adult patients undergoing scheduled chest x-ray examinations at the Erasme University Hospital (Brussels, BE) were recruited for paired examinations using EOS (at 50% dose) and DR. Paired data and images were compiled. Image data sets were independently scored by 4 radiologists according to the European Quality Criteria in Diagnostic Imaging, with additional challenges, such as scoring of thin anatomical structures. The dosimetry data obtained were also compared to those of CR, and experimental laboratory data were compiled on collimation and detector performance. Results: 37 of 40 cases were available for complete analysis. EOS chest examinations were acquired with a 13,5% repeat rate. Radiation dose (PA) was higher for EOS (0.22 mGy) than with DX (0.05), but less than CR or reference doses (0.3 mGy). Noise and ripple artifacts lowered the MTF (Modulation Transfer Function) to 1-1.5 pl/mm. Image quality scores between EOS and DX were comparable, but with better scores for EOS in several items as air-ways, mediastinum or anatomic coverage. Conclusion: EOS is feasible for chest imaging and is compliant with the chest reference doses. Radiation dose was higher than with DR, but lower than with CR, achieved by suppressing scatter. EOS image quality scores were not significantly inferior from those of DR, even for thin structures, as the extended density resolution and absence of scatter of EOS compensated for the inferior spatial resolution. Further development is needed to reach better dose containment and improve resolution, with validation in patients having various clinical conditions.
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Guimarães, dos Santos Rafael. "Ayahuasca: physiological and subjective effects, comparison with d-amphetamine, and repeated dose assessment." Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/83979.
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La Ayahuasca es una infusión psicotrópica Amazónica que combina el agonista 5-HT2A N,N-dimetiltriptamina (DMT) y los alcaloides β-carbolínicos inhibidores de la monoaminooxidasa (MAO) que hacen que la DMT sea activa oralmente. La infusión, obtenida de las plantas Banisteriopsis caapi y Psychotria viridis, es utilizada tradicionalmente con propósitos religiosos, rituales y medicinales por los grupos indígenas de la región. Más recientemente, el uso religioso sincrético de la ayahuasca se ha expandido por muchos países de Europa y de América.
Debido a la expansión mundial del uso de la ayahuasca, se han realizado dos estudios clínicos para caracterizar mejor su farmacología. En el estudio 1 exploramos: a) el impacto fisiológico de la ayahuasca tras su administración aguda en relación a los efectos autonómicos y neuroendocrinos; y b) los potenciales efectos de la ayahuasca en la inmunidad celular. En el estudio 2 evaluamos la farmacología de dos dosis repetidas de ayahuasca y la potencial aparición de tolerancia o sensibilización. Los dos estudios han sido conducidos en voluntarios jóvenes y sanos con experiencia en el uso de psicodélicos, utilizando una formulación liofilizada y encapsulada de ayahuasca administrada siguiendo un diseño aleatorio y doble-ciego.
En el estudio 1 se ha comparado una dosis de ayahuasca equivalente a 1.0 mg DMT/kg peso corporal vs. un placebo y vs. un fármaco de control positivo (20 mg d-anfetamina) en 10 voluntarios. Se han cuantificado los efectos autonómicos, neuroendocrinos e inmunitarios, además de las concentraciones plasmáticas de DMT, los efectos subjetivos y los neurofisiológicos (variables secundarias). La administración de ayahuasca produjo niveles plasmáticos de DMT mensurables y distintos efectos subjetivos y neurofisiológicos que no estaban presentes para la anfetamina. Los dos fármacos aumentaron el diámetro pupilar, produciendo la ayahuasca efectos de menor intensidad. Los niveles de prolactina aumentaron significativamente con la ayahuasca, pero no con la anfetamina; y los niveles de cortisol aumentaron con los dos fármacos, produciendo la ayahuasca efectos pico más intensos. La ayahuasca y la anfetamina indujeron modificaciones temporales similares en las subpoblaciones de linfocitos. El porcentaje de células CD4 y CD3 se vio reducido, y el de células NK aumentado. Los efectos máximos ocurrieron sobre las 2 horas, volviendo a los valores basales a las 24 horas. En conclusión, la ayahuasca ha demostrado efectos simpatomiméticos moderados, estimulación neuroendocrina significativa y efectos temporales de modulación de la inmunidad celular.
En el estudio 2, nueve voluntarios han recibido las dos siguientes combinaciones de tratamientos al menos con una semana de blanqueo: a) un placebo de lactosa y 4 horas después una dosis de ayahuasca; y b) dos dosis de ayahuasca separadas por 4 horas. Todas las dosis de ayahuasca son equivalentes a 0.75 mg DMT/kg peso corporal. Han sido evaluados los efectos subjetivos, neurofisiológicos, cardiovasculares, autonómicos, neuroendocrinos, y medidas de inmunidad celular. Las concentraciones plasmáticas de DMT, las puntuaciones en medidas subjetivas y neurofisiológicas, y los niveles de prolactina y cortisol fueron significativamente más intensos después de la segunda dosis administrada. Cuando los efectos han sido controlados por las concentraciones plasmáticas de DMT, no se observó ninguna diferencia para los efectos subjetivos, neurofisiológicos, autonómicos o inmunitarios. Por otro lado, se observó una tendencia para efectos reducidos en la presión sistólica y en la frecuencia cardíaca, y una reducción significativa para la hormona del crecimiento (GH) después de la segunda dosis. En conclusión, mientras no se ha demostrado tolerancia o sensibilización clara en le esfera psicológica o en la mayor parte de las variables fisiológicas, se ha observado una tendencia para efectos cardiovasculares de menor intensidad, juntamente con una tolerancia significativa para la secreción de GH.Ayahuasca is an Amazonian psychotropic plant tea combining the 5-HT2A agonist N,N-dimethyltryptamine (DMT) and monoamine oxidase (MAO)-inhibiting β-carboline alkaloids that render DMT orally active. The tea, obtained from Banisteriopsis caapi and Psychotria viridis, has traditionally been used for religious, ritual and medicinal purposes by the indigenous peoples of the region. More recently the syncretistic religious use of ayahuasca has expanded to many countries in Europe and the Americas. In view of the expanding use of ayahuasca worldwide, two clinical studies were conducted to further characterize the human pharmacology of ayahuasca. In study 1 we explored: a) the physiological impact of acute ayahuasca administration in terms of autonomic and neuroendocrine effects; and b) the potential effects of ayahuasca on cell-mediated immunity. In study 2 we assessed the pharmacology of ayahuasca in repeated doses and the potential occurrence of acute tolerance or sensitization. Both studies were conducted in healthy young volunteers with experience with psychedelics, using an encapsulated freeze-dried formulation of ayahuasca administered according to randomized double-blind designs. In study 1 an ayahuasca dose equivalent to 1.0 mg DMT/kg body weight was compared vs. a placebo and vs. a positive control (20 mg d-amphetamine) in 10 volunteers. Autonomic, neuroendocrine and immunomodulatory effects were measured in addition to DMT blood concentrations, subjective and neurophysiological effects (secondary variables). Ayahuasca led to measurable DMT plasma levels and distinct subjective and neurophysiological effects which were absent after amphetamine. Both drugs increased pupillary diameter, with ayahuasca showing milder effects. Prolactin levels were significantly increased by ayahuasca but not by amphetamine; and cortisol was increased by both, with ayahuasca leading to higher peak values. Ayahuasca and amphetamine induced similar time-dependent modifications in lymphocyte subpopulations. Percent CD4 and CD3 were decreased and NK cells increased. Maximum changes occurred around 2 hours, returning to baseline levels at 24 hours. In conclusion, ayahuasca displayed moderate sympathomimetic effects, significant neuroendocrine stimulation and a time-dependent modulatory effect on cell-mediated immunity. In study 2, nine volunteers received the two following treatment combinations at least one week apart: a) a lactose placebo and then 4 hours later an ayahuasca dose; and b) two ayahuasca doses 4 hours apart. All ayahuasca doses were equivalent to 0.75 mg DMT/kg bodyweight. Subjective, neurophysiological, cardiovascular, autonomic, neuroendocrine, and cell immunity measures were assessed. DMT plasma concentrations, scores in subjective, and neurophysiological variables, and serum prolactin and cortisol were significantly higher after two consecutive doses. When effects were standardized by plasma DMT concentrations, no differences were observed for subjective, neurophysiological, autonomic, or immunological effects. However, we observed a trend to reduced systolic blood pressure and heart rate, and a significant decrease for growth hormone (GH) after the second dose. In conclusion, whereas there was no clear-cut tolerance or sensitization in the psychological sphere or most physiological variables, a trend to lower cardiovascular activation was observed, together with significant tolerance to GH secretion.
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McVeigh, Gary Eugene. "An assessment of the antihypertensive efficacy and clinical pharmacology of low dose cyclopenthiazide." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317053.
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Han, EunYoung. "Revised series of stylized anthropometric phantoms for internal and external radiation dose assessment." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010025.
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Kroner, Oliver. "The Alliance for Risk Assessment Dose-Response Framework: Practical Guidance for Risk Practitioners." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1314053236.
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Can, Ozgun. "Noise Assessment Of Shipyard Workers." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609538/index.pdf.
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ABSTRACT
NOISE ASSESSMENT OF SHIPYARD WORKERS
Can,Özgü
n M.Sc.,Department of Engineering Sciences Supervisor : Prof.Dr.Gü
lin Birlik May 2008,139 pages Noise is one of the most important health risks in workplaces worldwide and NIOSH identified noise as one of the 10 important occupational problems. In OSHA'
s hearing conservation amendment it is stated that in U.S., more than 5 million workers are exposed to potentially hazardous levels of noise in manufacturing and utilities. In 1981 OSHA estimated that, at least one million workers in industry had undergone occupational hearing loss. Ship building has been one of the most promising and rapidly growing industries in Turkey in the recent years. It comprises many production techniques and activities, requires qualified personnel and compliance with several class institutions making the job interesting for the enthusiastic engineers and workers. However shipyard workers are subject to high levels of noise besides other health risks. The aim of this study is to figure out the effect of noise on shipyard workers. For this purpose 2 factories, namely Factory 1 and Factory 2 in a shipyard were chosen and two methods were adopted. The first method was the subjective evaluation of the workers through questionnaires distributed to them, whereas the second method involved the noise level measurement during their work hours. At all the points in Factory 1 where noise level measurements have been done, higher A-weighted values of noise than the limits stated in the legal regulations were found. In Factory 2, noise levels were all below the action value of 85 dBA .Dose measurements of the workers displayed the extremely variable acoustical conditions that the workers encountered. According to the &ldquo
Noise Regulation&rdquo
of Ministry of Labour and Social Security and &ldquo
The European Noise Directive&rdquo
, the employer seems to be obliged to measure periodically and to assess the level of noise exposure of workers in Factory 1 and take immediately the necessary precautions. Ear plug performance and speech interference conditions were also examined.
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Judisch, Alexandra Lynae. "Towards an optimized low radiation dose quantitative computed tomography protocol for pulmonary airway assessment." Thesis, University of Iowa, 2015. https://ir.uiowa.edu/etd/1652.
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Lung disease affects tens of millions of Americans, making it one of the most common medical conditions in the United States. Many of these lung diseases are classified as chronic airway disease. Because of this, it is important to be able to catch the development early so as to begin treatment as soon as possible to delay the progression and subsequently monitor that progression. One method of doing so is the use of quantitative computed tomography (CT). Study of the airway anatomy can be quantified using such measures as minor inner diameter (MinD), major inner diameter (MajD), wall thickness (WT), inner area (IA), and outer area (OA). Changes in these measures can then be tracked over time to determine how the airways are being affected by disease. The challenge with the desired longitudinal imaging is that prolonged radiation exposure can be dangerous to the patient. In order to make longitudinal imaging more feasible, it is important to determine what quantitative measures can reliably be made at different radiations doses so as to optimize radiation dose and quantitative assessment.
Working to make this determination, three different radiation doses were tested to evaluate their quantitative outputs. A high dose (14.98 mGy), medium dose (6.00), and low dose (0.74 mGy) were used to image six different porcine subjects. Images were collected at these doses both while the lungs were in-vivo and once the lungs had been fixed and excised ex-vivo. All of the scans were then processed using APOLLO (VIDA Diagnostics). From the complete airway trees, quantitative measures were collected from thirty-five airways. For the whole lung analysis, the medium and low dose in-vivo scans and the high dose ex-vivo scans were compared to the high dose in-vivo scans to compare assess MinD, MajD, WT, IA, and OA. Then, in order to determine how well the CT measures represent the actual anatomy, a total of thirteen cube samples containing airways were segmented from one of the lungs (based on volume analysis of the lung pre- and post-fixation and visual inspection). The cubes were imaged in CT, for the purpose of aiding in the establishment of original location and studying the effect of a narrowed imaging window, and microscopic CT (μCT). Since μCT can have a resolution on the scale of microns, the values measured in these images were considered ground-truth. The CT and μCT cubes were then registered to the high dose ex-vivo scan so as to compare the cube values with the ex-vivo values from each of the three doses. The same five measures were collected and analyzed.
The MinD, MajD, WT, IA, OA were statistically analyzed between the three in-vivo radiation dose scan sets, the high dose in- and ex-vivo scans, and the µCT cube, CT cube, and the three ex-vivo radiation dose sets. Preliminary results for the in-vivo scans show that the low dose and medium dose scans can reliably (< 5% error) be used to evaluate airways with minor diameters between 3.42 mm and 10.34 mm and major diameters between 3.98 mm and 12.06 mm. Comparison of the high-dose in-vivo and ex-vivo scans showed that the fixation and excision of the lungs did not significantly affect the ex-vivo lungs' ability to be used as a model for the in-vivo lungs. Finally, analysis of the various forms of the ex-vivo airways showed that there were few statistically significant differences between the datasets.
These results support the use of using the low (0.74 mGy) radiation dose when studying airway disease affecting airways with minor diameters between 3.42 mm and 10.34 mm and major diameters between 3.98 mm and 12.06 mm. They also show that the quantitative measures from CT are representative of the true measures of the airways.
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King'ori, Loti David. "The development and assessment of a fixed dose combination tablet of Ranitidine and Metronidazole." Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1013359.
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The oral route of drug administration is convenient since it is acceptable to most patients and the manufacturing processes used to produce tablets and capsules are relatively simple when compared to those used to manufacture other types of dosage forms. Metronidazole (MTZ) and Ranitidine (RTD) have been used in combination, as part of triple therapy for the treatment of ulcers. However the use of large numbers of tablets and long duration of therapy makes adherence to drug treatment challenging for patients. Therefore the formulation of a fixed dose combination (FDC) of MTZ and RTD may improve patient adherence to therapy and consequently may reduce morbidity and mortality due to ulcers. A stability indicating HPLC method for the simultaneous analysis of MTZ and RTD was developed and validated according to the International Conference on Harmonization (ICH) guidelines. The method was sensitive, selective, precise, accurate and linear.Preformulation studies were performed on the active pharmaceutical ingredients (API) alone and in combination with potential excipients. Differential scanning calorimetry (DSC) studies revealed a potential interaction between MTZ and RTD, however the interaction was not apparent following IR analysis of the same samples. DSC analyses of the API in combination with potential excipients revealed that the compounds were compatible with most materials with the exception of a binary mixture of RTD and Dibasic calcium phosphate (DCP) that exhibited a potential interaction. Thermal gravimetric analysis (TGA) of MTZ and RTD revealed that both compounds exhibited thermal stability. The Carrs Index (CI) and Hausner Ratio (HR) values of MTZ and RTD indicated that both compounds exhibited poor flow and compressibility properties, whereas the CI and HR values for (Microcrystalline cellulose) MCC and DCP indicated better flowability and compressibility characteristics.Direct compression and wet granulation processes were assessed to identify a suitable method of manufacture of FDC tablets of MTZ and RTD. The blends were evaluated using bulk and tapped density and the resultant tablets were evaluated for weight uniformity, crushing strength, tensile strength and disintegration time. The wet granulation method of manufacture produced tablets that showed acceptable pharmacotechnical properties: this approach was therefore used as the method of manufacture of FDC tablets of MTZ and RTD. Tablet formulations comprised of API, viz. MTZ and RTD and different compositions of MCC, DCP, Sodium starch glycolate (SSG) and Croscarmellose sodium (CCS), were manufactured in order to screen for an appropriate diluent and disintegrant composition for use in response surface studies. Assays of tablet content and in vitro drug release were undertaken using the validated HPLC method. Tablets in which MCC and CCS were used appeared to produce better assay and dissolution results as compared to those manufactured using DCP and SSG. Consequently a formulation comprised of MCC and CCS was selected and used in studies in which the effect(s) of level two formulation and composition changes as described in the Scale and Post Approval Changes for Immediate Release (SUPAC-IR) Guidelines on tablet disintegration and in vitro release were assessed. A Box-Behnken statistical design was used for the investigation of the effect of input factors, viz. CCS, (Polyvinyl pyrollidone K30) PVP-K30 and magnesium stearate on measured responses, viz. disintegration time and percent drug release in 10 minutes (Q10). CCS appeared to have an inverse linear relationship on disintegration time and a linear relationship with the Q10 for MTZ and RTD, whereas PVP-K30 and magnesium stearate appeared to have an antagonistic effect on the measured responses. Furthermore CCS and magnesium stearate exhibited an interaction that had an agonistic effect on the Q10 value for RTD. A numerical optimization approach was used to predict a formulation composition that would produce tablets that exhibited a disintegration time and Q10 values for MTZ and RTD that fell within the constraints set in our laboratory. The resultant model was found to be accurate and had a percent prediction error of < 5% for all measured response variables.FDC tablets of MTZ and RTD have been successfully produced. The disintegration of the tablet and dissolution of the API were within compendial specifications and the tablets are of suitable quality and have the potential to be further investigated to reduce the pill burden in the treatment of ulcers.
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Hwang, Beom Seuk. "Semiparametric Bayesian Joint Modeling with Applications in Toxicological Risk Assessment." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366327467.
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FONSECA, LEANDRO M. da. "Avaliação da radioatividade natural em tintas de uso comercial no Brasil." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26616.
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A radioatividade natural presente em solos, rochas e materiais de construção, devida ao 40K e às séries radioativas do 232Th e 238U é a principal contribuição à exposição externa aos seres humanos. Neste trabalho, determinou-se as concentrações de atividade de 226Ra (da série do 238U), 232Th e 40K presentes em 50 amostras de tintas látex de cor branca comercializadas no Brasil, especificamente, 15 do tipo econômico, 15 do tipo standard, 20 do tipo premium e em uma amostra de dióxido de titânio. As amostras foram seladas e armazenadas por um período mínimo de 30 dias para se alcançar o equilíbrio radioativo secular nas séries do 238U e do 232Th e medidas pela técnica analítica de espectrometria gama de alta resolução. As concentrações de atividade foram calculadas utilizando-se as médias ponderadas pelas incertezas do 214Pb e 214Bi para o 226Ra e médias ponderadas pelas incertezas do 228Ac, 212Pb e 212Bi para o 232Th. A concentração de atividade do 40K foi determinada pela sua transição única de 1460,8 keV. Fatores de autoatenuação gama foram calculados e utilizados para correção da concentração de atividade das amostras com densidade maior que 1,0 g.cm-3. Os índices radiológicos equivalente em rádio (Raeq), índice de concentração de atividade (Iγ), índice de risco à exposição gama interna (Hin), o índice de risco à exposição gama externa (Hex) e a taxa de dose (D) e dose efetiva anual (Def) foram calculados a partir das concentrações de atividade do 226Ra, 232Th e 40K. As concentrações de atividade de 226Ra das tintas variaram entre valores abaixo da atividade mínima detectável e 38,7 Bq.kg-1, as de 232Th variaram entre valores abaixo da atividade mínima detectável e 101,2 Bq.kg-1 e as de 40K variaram entre valores abaixo da atividade mínima detectável e 256 Bq.kg-1. O Raeq variou entre 1,41 Bq.kg-1 e 203 Bq.kg-1, o Iγ variou entre 0,0047 e 0,720, o Hin variou entre 0,0076 e 0,653 e o Hex variou entre 0,0038 e 0,549. A taxa de dose variou de 0,170 nGy.h-1 a 21,3 nGy.h-1 e a dose efetiva anual variou entre 0,83 μSv.a-1 e 104,2 μSv.a-1. Estes resultados mostram que as concentrações de atividades das tintas utilizadas neste estudo estão abaixo dos limites recomendados por Hassan et al. para Raeq (370 Bq.kg-1), pela Comissão Européia para o Iγ (limite de 2 para materiais superficiais) e pela Organização para Cooperação Econômica e Desenvolvimento para Hin e para Hex (ambos com limite de 1), para todas as 50 amostras estudadas, mostrando assim a segurança destas tintas com relação a proteção radiológica.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Phetxumphou, Katherine. "Novel Approaches to Exposure Assessment and Dose Response to Contaminants in Drinking Water and Food." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/94582.
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In the fields of water safety, food safety, and public communications, the overarching goal is to improve public health. Thus, this dissertation focuses on risk assessment and applying novel methods for exposure assessments and dose responses to contaminants in drinking water and foods. Factors that greatly impact contaminant exposures and human dose response include: population susceptibility (i.e., healthy adults or children), different routes of exposures (i.e., ingestion or inhalation), carrier matrices (i.e., water or food), and intricacies of chemical and biological mixtures. Chemical spills, such as the 2014 crude MCHM spill in Charleston, WV, revealed the complexities of both minor and major components in the chemical mixture. Slight shifts in geometric structures (isomers) can affect the fate and transport properties of the chemical mixture and as a result, the level of human exposure and dose response to each component in the chemical mixture. Odorous properties of both minor and major components can affect human inhalation exposure, especially during showering, and can be as detrimental as the ingestion route exposure and are different for healthy adults versus for children. Food contaminants, such as Shiga toxin producing Escherichia coli (STEC) in beef products, can be mitigated through a quantitative microbial risk assessment (QMRA) framework that follows a farm-to-fork model. Methods to ensure greatest microbial reduction include: employed intervention strategies at slaughter plants (i.e., water washing of beef carcass), improved cooking times and temperature methods at the consumer and retail level, and assessed minimum effective dose response modeling for different population susceptibilities. Current public communication tools, including the Drinking Water Taste-and-Odor Wheel or Consumer Confidence Reports (better known as water quality reports), should be redeveloped to uphold water safety. Furthermore, public health campaigns that uses social media strategies and informative websites can better educate the public on food contaminants. Ultimately, the objective is to prevent human illnesses due to water contaminants and foodborne pathogens and to bridge the communication gap between the consumers and the experts concerned with water and food safety.Ph. D.
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Tseng, Hsin-Wu. "Task-Based Image Quality Assessment in X-Ray Computed Tomography." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/593630.
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In X-Ray CT, there is always a desire to maintain the image quality while reducing the radiation dose. Recently several dose reduction approaches in both software and hardware have been developed to achieve the goal of making radiation as low as possible. Thus, the assessment of image quality becomes an important factor for routine quality control of medical X-Ray devices. In this work, task-based image quality measurements using model observers were used to evaluate the performance of X-Ray CT systems. To evaluate the dose reduction ability, detection tasks as well as combined detection and estimation tasks were considered. In detection tasks and combined detection and estimation tasks, the channelized Hotelling observer (CHO) and channelized scanning linear observer (CSLO) (with Dense Difference of Gauss channels) were employed respectively. They were used to evaluate the dose reduction capability of the iterative reconstruction algorithm developed by GE compared to the traditional reconstruction algorithm, filtered backprojection (FBP). Additionally, CHO and CSLO were also used for optimization of CT protocols. Our methods were also applied to Cardiac CT systems for temporal resolution evaluations. Two reconstruction algorithms, FBP and the motion correction algorithm, Snapshot Freeze (SSF), operated at two heart-beating rates with two reconstruction windows were quantitatively evaluated using task-based measurements. Finally, due to the huge demand of data acquisitions in the conventional channelized model observers, a proposed High-Dose-Signal-LOOL CHO/CSLO (HL-CHO/CSLO) that could efficiently reduce the data requirement has also been investigated in the pure detection, and combined detection and estimation task. In all studies, the practicality and the use of real data is emphasized. The results of all these studies demonstrate the usefulness of the task-based measurements of image quality in X-Ray CT imaging.
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Marina, Zdraveska Kochovska. "Effective dose estimation and risk assessment in patients treated with iodine 131I using Monte Carlo simulation." Phd thesis, Univerzitet u Novom Sadu, Asocijacija centara za interdisciplinarne i multidisciplinarne studije i istraživanja, 2014. http://www.cris.uns.ac.rs/record.jsf?recordId=90158&source=NDLTD&language=en.
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The most frequently used radiopharmaceutical for treatment of thyroid diseases such as Thyroid Cancer and Hyperthyroidism is radioactive iodine 131I. It has a very high success rate in treatment of patients with thyroid diseases and also it has been proven to be safe and relatively inexpensive treatment modality. Whenever radiation is used in the treatment of the benign or cancer diseases dosimetry is essential. The main aim of this study is to perform external measurements of dose rate after administered activity and to simulate dosimetry of internal organs and risk assessment using MCNP 4b code, either for thyroid cancer and Hyperthyroid patients. To search safety optimization in this kind of therapy, it was recognized the necessity of more accurate knowledge of dose levels received by stomach and other organs. Of great importance is to know the effective dose that will be reached in gastric and other surrounding organs such as liver, lung, bladder etc. Additional aim was to provide information to be used in the improvement of radiation therapy, radiation safety practices and improvement of the fundamentals of radiation protection as defined by ICRP: justification, optimization and application of dose limits. The significance of this research is that the doses to internal organs can be determined and it worth to mention that such internal dosimetry calculation has been performed rare in the field of nuclear medicine. In accordance with the calculations carried out during this study and reference available in the literature that the therapy with radioiodine will be improved at the Institute of pathophysiology and nuclear medicine. Designed quality programs will be useful also for regulatory and accreditation bodies in the process of accreditation and radiation protection strategy. This work is divided into interconnected chapters. Chapter 2 to 4 contains the literature review and theoretical background of the study. Chapter 3 covers material and methods and aspect of Monte Carlo transport code focused on MCNP 4b code. Chapter 4 provides the results and discussion of the findings. Conclusions and recommendations are discussed in Chapter 5. Chapter 6 contains references used in this work.Cilj terapije sa radiaoktivnim jodom 131I kod pacijenata koji boluju od nekih tipova tiroidnih carcinoma i hipertiroidizma je isporuka doze i apsorpcija doze u tiroidnoj žlezdi. Terapija sa radioaktivnim jodom sprovodi se u obliku rastvora Na131I (natrijum jodida) u tečnoj formi ili aplicira se u formi kapsule. Efektivna doza je rezultat apsorbovane doze u tiroidnom tkivu, ali i ostali unutrašnji organi prime izvesnu dozu. Kapsule koje sadrže natrijum jodid ostaju u stomaku oko 15 minuta pre nego što započne apsorpcija, vreme dovoljno dugo za rizično izlaganje. Ova činjenica je jedan od ciljeva doktorske teze, odrediti efektivnu dozu u stomaku i nekoliko unutrašnjih okolnih organa modelovanje transporta i interakcije gama zračenja i beta čestica emitovanih iz radionuklida 131I je korišćen Monte Karlo kod (MCNP4b). Radiojod je modelovan kao tačkasti izvor na dnu stomaka. Proračunavana je apsorbovana energija po jedinici transformacije u stomaku i okolnim organima. Ekvivalentna doza u tim organima je izračunata da bi se odredila efektivna doza primenom odgovarajućih težinskih faktora. Dobijeni rezultati imaju značaja za zaštitu od zračenja, ali su važni i za ustanovljavanje novih kalibracionih procedura kao deo sigurnosne kontrole i kontrole kvaliteta u proizvodnji i kontroli radiofarmaceutika kao i procedure administriranja radiofarmaceutika i primene bolnčikih puteva. Smatramo da če rezultati ovog istraživanja poboljšati bezbednosnu kulturu u našem sistemu zdravstvene zaštite kao i u državnim organima koji kreiraju i donose regulative.
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Dybwad, Anniken. "Comparison of Dose Distributions resulting from IMRT and VMAT, and Assessment of MLC Leaf Positioning Errors." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22432.
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Intensity-modulated radiotherapy (IMRT) is a radiation technique used in the treatment of head-and-neck cancer patients. IMRT results in a dose distribution which conforms to the tumor volume(s), and therefore sparing surrounding normal tissue. However, the radiation delivery is relatively time consuming. Volumetric modulated arc therapy (VMAT) on the other hand, has a radiation delivery time down to one third compared to that of IMRT (depending on number of arcs, arc lengths etc.). This shortened treatment time will allow more treatments per day, and a decrease in discomfort which may be experienced by the patients undergoing radiotherapy. Due to the differences in radiation delivery time, it is of interest to compare the dose distributions resulting from IMRT and VMAT radiation treatment plans.In this study, ten head-and-neck cancer patient cases were used to compare the modalities step-and-shoot IMRT, single-arc VMAT, dual-arc VMAT (two arcs of 356$^\circ$ each) and short dual-arc VMAT (two arcs of 270$^\circ$ each). The Delta4 phantom from ScandiDos was used to measure the resulting dose distributions from each of the 40 radiation treatment plans (4 modalities, 10 patient cases). Each measured dose distribution was then compared with its corresponding calculated phantom dose distribution, which was obtained in Oncentra MasterPlan (treatment planning system) by using artificial CT-images representing the phantom's composition and dimensions.The gamma index was used as the comparison parameter, and the percentage of gamma index values which were $\leq$1 defined the agreement between a measured and calculated dose distribution. The gamma index criteria were set to allow max dose deviation and max spatial deviation of $\pm$3,0$\%$ and $\pm$3,0~mm respectively, and the deviations were normalized to local dose.In order to further compare the radiation modalities, different dose parameters were retrieved from the calculated patient dose distributions resulting from each of the four modalities. The parameters which were assessed were mean dose to parotis, maximum dose to medulla spinalis, homogeneity index for certain treatment volumes (PTVs), and Jaccard index (conformity index) for all treatment volumes combined. The radiation delivery time was also measured for each treatment modality used in this study.In the second part of this study, two systematic MLC leaf positioning errors (MLCpe) were introduced to the treatment plans single-arc VMAT, dual-arc VMAT (two arcs of 356$^\circ$ each) and IMRT of all ten patient cases. The two error-types consisted of 1) a +1~mm shifting of each MLC leaf (opening of aperture), and 2) a -1~mm shifting of each MLC leaf (closing of aperture). The dose distributions resulting from the MLCpe treatment plans, as well as the error-free plans, were measured using the Delta4 phantom. The effects of the errors were evaluated by calculating the relative deviation in mean, minimum and maximum dose within certain chosen volumes.The obtained percentages of gamma index values $\leq$1, show that the accordance between measured and calculated dose distributions was best for the modality IMRT. However, all four treatment modalities had percentages satisfying the pass/fail criteria used at the Department of Radiotherapy (St.\ Olav's Hospital). In terms of the dose parameters which were retrieved from the calculated patient dose distributions, the largest differences between modalities were seen in radiation delivery time and homogeneity index. The three VMAT modalities had markedly shorter radiation delivery times compared to IMRT. The homogeneity indexes, which were calculated for two chosen treatment volumes (PTVs), indicate that the modalities dual-arc and short dual-arc result in best homogeneity for the two volumes, whereas IMRT results in the poorest.The relative deviations in various dose parameters, due to systematic MLC leaf positioning errors (MLCpe), indicate that the VMAT modalities single-arc and dual-arc are generally more affected by systematic MLCpe compared to IMRT. However, for all three evaluated modalities, unwanted clinical effects due to systematic MLCpe may occur for all assessed volumes, due to relatively large deviation percentages.
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Lee, Choonik. "Development of the voxel computational phantoms of pediatric patients and their application to organ dose assessment." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013660.
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Nelms, Mark David. "Development of in silico models to support repeat dose safety assessment of cosmetic ingredients to humans." Thesis, Liverpool John Moores University, 2015. http://researchonline.ljmu.ac.uk/4424/.
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Cosmetic products are used daily on a global scale. Therefore, it is necessary to ensure that these products, and their ingredients, do not cause any adverse human health effects under normal usage; to ensure this, risk assessment must be performed. Traditionally, risk assessments are performed in vivo, i.e. conducting tests on animals using the chemical(s) of interest. However, over the past decade there has been an increase in research into the use of alternative toxicity testing methods, such as in vitro, in chemico and in silico. Whilst there are a number of alternative techniques that may be employed, no one method can be used in isolation as a full replacement for an in vivo test. Therefore, the Adverse Outcome Pathway (AOP) concept is an emerging method by which information provided by the in vitro, in chemico, and in silico approaches can be utilised in an integrated testing strategy. The AOP concept links an upstream molecular initiating event to a downstream adverse outcome, via a number of testable key events. In silico approaches utilise computers in order to develop predictive models. Within the AOP paradigm in silico method work to identify the key features of a chemical (structural alerts) that induce a molecular initiating event (MIE). A collection of structural alerts that induce the same MIE are considered to be an in silico profiler. Typically, these in silico profilers are supported by associated toxicity, or mechanistic, information pertaining to the ability to induce a specific MIE. The overall aim of the work presented in this thesis was the development of an in silico profiler, based upon the hypothesis that the induction of mitochondrial toxicity is a key driver of organ-level toxicity. The research presented herein demonstrates the ability to identify, and develop, two types of structural alert; mechanism- and chemistry-based; that pertain to mitochondrial toxicity. Due to the differences inherent in these two types of alert they should be utilised for different purposes. As such, the main usage of the mechanism-based alerts should be in the formation of chemical categories and subsequent data gap filling via read-across. In comparison, the chemistry-based alerts should be utilised for the purposes of prioritising chemicals, within an inventory, that should undergo additional testing in in vitro and/or in chemico assays. It is envisaged that these two types of structural alerts could be used to profile chemical inventories as part of a tiered testing strategy. Therefore, the future work discussed in detail the need to expand the chemical space covered by the alerts. Additional future work involves utilising experimental information from in vitro/in chemico assays to verify the mechanism-based alerts and to refine the chemistry-based alerts by discerning mechanistic information associated with them. Furthermore, it is envisaged that these alerts could be incorporated into predictive tools, such as the OECD QSAR Toolbox, to enable their use for screening and prioritisation purposes.
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Henderson, Alastair. "Low dose-rate brachytherapy for early prostate cancer : patient selection and assessment of patient reported outcomes." Thesis, University of Surrey, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486095.
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Introduction I Low dose-rate brachytherapy is an accepted treatment for early prostate cancer in the UK. This thesis reports studies of clinical outcome from this treatment in a UK centre. Patients and Methods Prospective observational study in three areas of outcome for patients undergoing low' dose-rate (LDR) seed brachytherapy implants: . 1. Quality of life questionnaires were used to prospectively assess toxicity of 3 LDR brachytherapy treatments: monotherapy+l- androgen deprivation+lexternal beam radiotherapy in a longitudinal study. ii. Post-implant catheter use was correlated with preoperative variables (prostate volume, androgen deprivation, urodynamic obstruction status and IPSS score) and treatment indices (prostate D90, Urethral DIO, D25, and D50). 1lI. Bicalutamide and goserelin for pre-brachytherapy prostate volume reduction. Results General health related quality of life was 'a little' to 'moderately' decreased 6weeks after brachytherapy, but unchanged by clinically significant amounts >9 months after any brachytherapy treatment. Permanent problematic urinary incontinence «4%) and significant bother from use of incontinence aids «3%) were rare after any - 4- brachytherapy subtype. Urinary problems, principally frequency and urgent micturition worsened after brachytherapy with peak 'very much' worsened symptoms at 6-weeks post treatment and improvements to 'a little' worse than baseline at 1-2 years. Sexual function declined significantly in potent men with partners who underwent brachytherapy. By 2 years post brachytherapy, almost half of men who were potent before brachytherapy as monotherapy started using phosphodiesterase inhibitors (e.g. Viagra®). Despite this medication, at least 47% rep'orted moderatesevere erectile dysfunction. Postoperative need for catheterisation was predicted by elevated prostate volume (>35cc), raised IPSS score (>7 vs. <7), and urodynamic obstruction (vs. equivocal or unobstructed patients). Bicalutamide produced smaller reductions in prostate volume than Goserelin (-8 vs. -26% reduction in volume). Conclusions Clinically significant changes in HRQOL were present at >12m but they were of small magnitude except for sexual side effects which continued to be common and marked. Use of an IPSS score, prostate volume and urodynamic assessment may improve selection of patients for brachytherapy. Bicalutamide is superior to goserelin for prostate cytoreduction prior to brachytherapy.
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Davidson, Sarah E. "Alternative Approach to Dose-Response Modeling of Toxicogenomic Data with an Application in Risk Assessment of Engineered Nanomaterials." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627666554729205.
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Palit, Robin. "Computational Tools and Methods for Objective Assessment of Image Quality in X-Ray CT and SPECT." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/268492.
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Computational tools of use in the objective assessment of image quality for tomography systems were developed for computer processing units (CPU) and graphics processing units (GPU) in the image quality lab at the University of Arizona. Fast analytic x-ray projection code called IQCT was created to compute the mean projection image for cone beam multi-slice helical computed tomography (CT) scanners. IQCT was optimized to take advantage of the massively parallel architecture of GPUs. CPU code for computing single photon emission computed tomography (SPECT) projection images was written calling upon previous research in the image quality lab. IQCT and the SPECT modeling code were used to simulate data for multimodality SPECT/CT observer studies. The purpose of these observer studies was to assess the benefit in image quality of using attenuation information from a CT measurement in myocardial SPECT imaging. The observer chosen for these studies was the scanning linear observer. The tasks for the observer were localization of a signal and estimation of the signal radius. For the localization study, area under the localization receiver operating characteristic curve (A(LROC)) was computed as A(LROC)^Meas = 0.89332 ± 0.00474 and A(LROC)^No = 0.89408 ± 0.00475, where "Meas" implies the use of attenuation information from the CT measurement, and "No" indicates the absence of attenuation information. For the estimation study, area under the estimation receiver operating characteristic curve (A(EROC)) was quantified as A(EROC)^Meas = 0.55926 ± 0.00731 and A(EROC)^No = 0.56167 ± 0.00731. Based on these results, it was concluded that the use of CT information did not improve the scanning linear observer's ability to perform the stated myocardial SPECT tasks. The risk to the patient of the CT measurement was quantified in terms of excess effective dose as 2.37 mSv for males and 3.38 mSv for females.Another image quality tool generated within this body of work was a singular value decomposition (SVD) algorithm to reduce the dimension of the eigenvalue problem for tomography systems with rotational symmetry. Agreement in the results of this reduced dimension SVD algorithm and those of a standard SVD algorithm are shown for a toy problem. The use of SVD toward image quality metrics such as the measurement and null space are also presented.
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Vaughn, Michelle Lynn. "Internal dose assessment calculations for the proposed low-level radioactive waste disposal facility in the southeast compact." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/17378.
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Staton, Robert J. "Organ dose assessment in pediatric fluoroscopy and CT via a tomographic computational phantom of the newborn patient." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013050.
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Bolt, Matthew A. "Evidence based assessment of the clinical impact of dose variations arising in the clinical radiotherapy dosimetry chain." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/848888/.
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Objectives: The accuracy of delivered dose depends directly upon initial beam calibration and subsequent maintenance of this beam output. The uncertainty associated with these measurements and its impact on clinical outcomes is not well documented. This work gives an evidence based approach to determining this variation and its clinical impact. Novelty: This work will quantify for the first time the variations present in the routine maintenance of beam output on a national scale. The novel application of these dosimetric uncertainties to radiobiological models is then employed to predict the variation in clinical outcome due to the quantified dosimetric variations for specific clinical cases, including both tumour control and associated treatment complications on both individual and patient populations. Results: The linear-quadratic and Lyman Kutcher Burman models have been implemented to allow flexibility in the modelling of individual patient doses on a fraction by fraction basis. The variation in delivered doses due to beam output variations is seen to be normally distributed with a standard deviation of 0.7%. These variations may lead to a typical patient experiencing a range in treatment outcome probabilities of over 10% for cancers with a steep dose response curve such as head and neck in both the case of an individual patient and for a patient population. Conclusions: The precise control of beam output is shown to be a major factor in the overall uncertainty for dose delivery in modern treatment techniques. With reductions in other uncertainties in radiotherapy treatments, now may be the time to consider reduction of tolerance levels to allow optimal patient treatment and outcomes.
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Suleiman, Reem Abdallah S. "Post-market assessment of the quality of first line regimen fixed-dose combination antiretrovirals in South Africa." Thesis, University of the Western Cape, 2017. http://hdl.handle.net/11394/6183.
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Magister Scientiae - MSc (Pharmaceutical Chemistry)The rapid increase in access to new antiretrovirals (ARVs) worldwide and, especially in sub-Saharan Africa, coupled with the well-documented problem of poor quality ARVs in developing countries has underscored the need for quality assessment of these medicines. South Africa has the worst human immunodeficiency virus (HIV) epidemic profile in the world; consequently, it has rolled out the world's largest antiretroviral ARV programme. With increasing market penetration of generic medicine in South Africa and especially ARVs, there is a call for stringent quality control mechanisms following the marketing approval (post-market quality control) of these medications. Unfortunately, evidence suggests that the World Health Organisation (WHO) recommendations for this aspect of quality assurance is not met by most Medicine Regulatory Authorities. In South Africa and many other countries this is attributed to a lack of physical and financial resources to enforce effective post-marketing surveillance (PMS) of all pharmaceuticals available in the country.
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Farias, Juliano Ricardo. "Resistance risk assessment of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) to Cry1F protein from Bacillus thuringiensis Berliner in Brazil." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/11/11146/tde-04022014-150013/.
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The event TC1507 maize with cry1F gene from the bacterium Bacillus thuringiensis Berliner (Bt) was approved for commercial release in Brazil in 2008. The evolution of pest resistance to Bt plants has been a great concern to preserve the lifetime of this technology. Therefore, in this study we assess the risk of evolution of resistance to Cry1F protein in Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) populations from major maize-growing regions in Brazil. The baseline susceptibility to Cry1F was detemined with diet overlay bioassay for susceptible reference population and four field populations of S. frugiperda. Then, we monitored 43 populations of S. frugiperda sampled in nine different States of Brazil during 2010/2011, 2011/2012 and 2012/2013 crop seasons. Only 4-fold variation in susceptibility to Cry1F was detected among S. frugiperda from field populations in the baseline susceptibility study. Diagnostic concentration of 2,000 ng cm-2 was defined for monitoring the susceptibility to Cry1F in S. frugiperda populations. Survival at 2,000 ng cm-2 of Cry1F protein increased significantly throughout crop seasons in populations from São Paulo, Santa Catarina, Rio Grande do Sul, Bahia, Mato Grosso, Goiás, Mato Grosso do Sul, and Paraná, but not in Minas Gerais. We also sampled a population of S. frugiperda in TC1507 field failures in Bahia in October, 2011. This population was selected in laboratory with Cry1F protein up to 20,000 ng cm-2 and the resistance ratio of the selected resistant population (BA25R) was > 5,000-fold. This resistant population was able to survive in Cry1F maize from neonate till pupa and produce normal adult. The inheritance of S. frugiperda resistance to Cry1F protein was autosomal. To test the functional dominance, neonate larvae obtained from the cross of resistant and susceptible populations were tested in leaf bioassay, and around 8% of heterozygotes were able to survive and complete the larval development and produce normal adults on TC1507 leaves while susceptible larvae could not survive for up to five days after infestation. Dominance was estimated to be 0.15 ± 0.09, suggesting that resistance to Cry1F in TC1507 maize was incompletely recessive. We also conducted resistance selection studies in other seven S. frugiperda populations from six different Brazilian states to test whether the resistance alleles were at same locus or not. The F1 larvae obtained from the cross between resistant population (BA25R) and each of the seven selected resistant populations were able to survive at 2,000 ng cm-2 of Cry1F protein in diet bioassay, and therefore they shared the same locus of resistance to Cry1F protein. We estimated the frequency of resistance allele to Cry1F protein in populations of S. frugiperda of main crop season 2011/2012 from five states. We stablished 517 isofemale lines using F2 screen method. The total frequency of Cry1F resistance allele in Brazil was 0.088 with 95% confidence interval between 0.077 and 0.100. Based on results obtained in this study, the risk of resistance evolution to Cry1F protein by S. frugiperda is high in Brazil.O evento de milho TC1507 com gene cry1F da bactéria Bacillus thuringiensis Berliner foi aprovado comercialmente no Brasil em 2008. A evolução da resistência de pragas a plantas Bt tem sido uma grande preocupação na preservação desta tecnologia. Portanto, neste estudo foi avaliado o risco de evolução da resistência à proteína Cry1F em populações de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) das principais regiões de cultivo de milho no Brasil. A linha-básica de suscetibilidade à proteina Cry1F foi determinada em bioensaio de aplicação superfícial na dieta para a população suscetível de referência e quatro populações de campo de S. frugiperda. Posteriormente, a suscetibilidade a Cry1F foi monitorada em 43 populações de S. frugiperda coletadas em nove Estados do Brasil nas safras agrícolas de 2010/2011, 2011/2012 e 2012/2013. A variação na suscetibilidade foi de apenas quatro vezes para Cry1F entre as populações de campo na linha-básica de suscetibilidade. A concentração diagnóstica de 2.000 ng cm-2 de proteína Cry1F foi definida para o monitoramento da suscetibilidade. A sobrevivência em 2.000 ng cm-2 de proteína Cry1F aumentou significativamente no decorrer das safras em populações de São Paulo, Santa Catarina, Rio Grande do Sul, Bahia, Mato Grosso, Goiás, Mato Grosso do Sul e Paraná, mas não em Minas Gerais. Além disso, uma população de S. frugiperda foi coletada em milho TC1507 com falha de controle na Bahia em outubro de 2011. Esta população foi selecionada no laboratório com a proteína Cry1F até 20.000 ng cm-2, obtendo-se uma população resistente (BA25R) com razão de resistência >5000 vezes. Esta população resistente foi capaz de sobreviver no milho TC1507 desde larva neonata até a fase de pupa e com emergência de adultos normais. O padrão de herança da resistência de S. frugiperda a Cry1F foi autossômica. Para testar a dominância funcional, as larvas neonatas do cruzamento entre a população resistente e suscetível foram testadas em folhas do evento TC1507 e cerca de 8% dos heterozigotos foram capazes de sobreviver, completar o desenvolvimento e produzir adultos normais, enquanto as larvas da linhagem suscetível não sobreviveram por mais de cinco dias após a infestação. A dominância foi estimada em 0,15 ± 0,09; portanto, a resistência à proteína Cry1F no milho TC1507 foi incompletamente recessiva. A resistência foi selecionada para outras sete populações de seis Estados brasileiros para testar se os alelos de resistência estavam no mesmo locus. As larvas F1 obtidas do cruzamento entre a população resistente (BA25R) e cada uma das sete populações selecionadas sobreviveram na concentração de 2,000 ng cm-2 de proteína Cry1F e, portanto, essas populações compartilharam o mesmo locus de resistência à proteína Cry1F. A freqüência do alelo resistente à proteína Cry1F foi estimada em populações de S. frugiperda coletadas em cinco Estados na safra 2011/2012. Foram estabelecidas 517 isolinhas utilizando o método de \"F2 screen\". A freqüência total do alelo de resistência à proteína Cry1F no Brasil foi de 0,088, com intervalo de confiança de 95% entre 0,077 e 0,100. Com base nos resultados, o risco de evolução da resistência à proteína Cry1F por S. frugiperda é elevada no Brasil.
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Stolz, Christan. "Physical activity assessment and health outcomes in old age : how valid are dose-response relationships in epidemiologic studies /." [S.l.] : [s.n.], 2009. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Cros, Torrents Maria. "Dose assessment in Computed Tomography based on Monte Carlo simulation for a 320 detector-row cone-beam scanner." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/454717.
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La tomografia computaritzada (TC) ha esdevingut una de les tècniques d’imatge més utilitzades en el camp de radiodiagnòstic. Des de la introducció dels escàners TC multidetector, el ràpid procés d’evolució tecnològica ha permès l’ús de noves aplicacions diagnostiques. Per aquest motiu, és de gran importància l’avaluació d’exposició de radiació en els escàners i protocols d’adquisició actuals amb l’objectiu d’optimitzar l’aplicació clínica del TC i de minimitzar els possibles efectes de la radiació per la salut. La motivació d’aquesta tesi fou el desenvolupament d’una eina de simulació basada en Monte Carlo (MC) que reproduís totes les característiques de l’escàner de TC de feix cònic amb 320 files de detectors i les últimes recomanacions de la ICRP amb la finalitat d’avaluar dosis a pacients sotmesos a exploracions TC. Els quatre articles que conformen aquesta tesi descriuen el procés seguit per adaptar el model d’escàner al programa de simulació, la validació del codi de MC desenvolupat, l’ús del programa per a l’estimació de dosis en òrgans i dosis efectives en diferents exploracions TC de l’equip i el desenvolupament d’una eina de software dosimètrica per a l’avaluació de dosis. En conclusió, aquesta tesi presenta un marc de referència per una estimació de dosis precisa en pacients estàndard sotmesos a exploracions TC en un escàner de feix cònic amb 320 files de detectors.La tomografía computarizada (TC) se ha convertido en una de les técnicas de imagen más utilizadas en el campo del radiodiagnóstico. Desde la introducción de los escáneres TC multidetector, el rápido proceso de evolución tecnológica ha permitido el uso de nuevas aplicaciones diagnósticas. Por este motivo, es de gran importancia la evaluación de exposición de radiación en los escáneres y protocoles actuales de adquisición con el objetivo de optimizar la aplicación clínica del TC y de minimizar los posibles efectos de la radiación para la salud. La motivación de esta tesis fue el desarrollo de una herramienta de simulación basada en Monte Carlo (MC) que reprodujera todas las características técnicas del escáner de TC de haz cónico con 320 hileras de detectores y las últimas recomendaciones de la ICRP con el objetivo de evaluar dosis en pacientes sometidos a exploraciones TC. Los cuatro artículos que forman esta tesis describen el proceso seguido para adaptar el modelo de escáner al programa de simulación, la validación del código MC desarrollado, el uso del programa para la estimación de dosis en órganos y dosis efectiva en distintas exploraciones TC del equipo y el desarrollo de una herramienta de software dosimétrica para la evaluación de dosis. En conclusión, esta tesis presenta un marco de referencia para una estimación de dosis precisa en pacientes estándar sometidos a exploraciones TC en un escáner de haz cónico de 320 hileras de detectores.
Computed Tomography (CT) has become one of the imaging techniques most used in the field of diagnostic radiology. Since the introduction of the multi-slice CT scanners, a continuous process of technological evolution has made possible a new range of diagnostic applications. For this reason, there is a need to be aware about radiation exposure in current scanners and current acquisition protocols in order to optimize the clinical application of CT and to minimize possible radiation-induced health effects. The motivation of this thesis was the development of a Monte Carlo (MC) simulation tool taking into account all relevant technical characteristics of the 320 detector-row cone-beam CT scanner and the latest recommendations of the ICRP with the aim of assessing doses in patients undergoing CT examinations. The four papers included in this thesis described the procedure followed to tailor the scanner model in a MC simulation program, the validation of the MC code, the use of the program for estimation of organ absorbed doses and effective doses in different CT examinations and the development of a dosimetric software tool for dose assessment and reporting. Hence, this dissertation presents a framework for an accurate dose estimates in standard patients undergoing CT examinations with a 320 detector-row cone-beam scanner.
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Lindström, Maria. "Particles in small airways : mechanisms for deposition and clearance & pharmacokinetic assessment of delivered dose to the lung /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7349-893-9/.
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Burau, Daniela [Verfasser]. "Assessment of dose optimisation requirements in special patient populations in the field of endocrinology and infectiology / Daniela Burau." Berlin : Freie Universität Berlin, 2021. http://nbn-resolving.de/urn:nbn:de:kobv:188-refubium-30071-5.
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Pesolillo, Daniele. "Image quality and dose evaluation of filtered back projection versus iterative reconstruction algorithm in multislice computed tomography." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8315/.
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Il presente lavoro di tesi è stato svolto presso il servizio di Fisica Sanitaria del Policlinico Sant'Orsola-Malpighi di Bologna.
Lo studio si è concentrato sul confronto tra le tecniche di ricostruzione standard (Filtered Back Projection, FBP) e quelle iterative in Tomografia Computerizzata.
Il lavoro è stato diviso in due parti: nella prima è stata analizzata la qualità delle immagini acquisite con una CT multislice (iCT 128, sistema Philips) utilizzando sia l'algoritmo FBP sia quello iterativo (nel nostro caso iDose4). Per valutare la qualità delle immagini sono stati analizzati i seguenti parametri: il Noise Power Spectrum (NPS), la Modulation Transfer Function (MTF) e il rapporto contrasto-rumore (CNR). Le prime due grandezze sono state studiate effettuando misure su un fantoccio fornito dalla ditta costruttrice, che simulava la parte body e la parte head, con due cilindri di 32 e 20 cm rispettivamente.
Le misure confermano la riduzione del rumore ma in maniera differente per i diversi filtri di convoluzione utilizzati. Lo studio dell'MTF invece ha rivelato che l'utilizzo delle tecniche standard e iterative non cambia la risoluzione spaziale; infatti gli andamenti ottenuti sono perfettamente identici (a parte le differenze intrinseche nei filtri di convoluzione), a differenza di quanto dichiarato dalla ditta. Per l'analisi del CNR sono stati utilizzati due fantocci; il primo, chiamato Catphan 600 è il fantoccio utilizzato per caratterizzare i sistemi CT. Il secondo, chiamato Cirs 061 ha al suo interno degli inserti che simulano la presenza di lesioni con densità tipiche del distretto addominale. Lo studio effettuato ha evidenziato che, per entrambi i fantocci, il rapporto contrasto-rumore aumenta se si utilizza la tecnica di ricostruzione iterativa.
La seconda parte del lavoro di tesi è stata quella di effettuare una valutazione della riduzione della dose prendendo in considerazione diversi protocolli utilizzati nella pratica clinica, si sono analizzati un alto numero di esami e si sono calcolati i valori medi di CTDI e DLP su un campione di esame con FBP e con iDose4. I risultati mostrano che i valori ricavati con l'utilizzo dell'algoritmo iterativo sono al di sotto dei valori DLR nazionali di riferimento e di quelli che non usano i sistemi iterativi.
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Harper, Robert. "Thiazide diuretics and insulin action : an assessment of the effects of low and conventional dose bendrofluazide on insulin action." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261769.
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Zhang, Wei, Xue Zhang, Yuling Tian, Yan Zhu, Yindong Tong, Ying Li, and Xuejun Wang. "Risk Assessment of Total Mercury and Methylmercury in Aquatic Products from Offshore Farms in China." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/2624.
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Contamination of methylmercury (MeHg) in aquatic products has been a wide spread health concern. The objective of this study is to determine total mercury (THg) and MeHg concentrations in different species of aquatic products from major offshore farms in China, and to assess health impacts from consumption. Results showed that the concentrations of THg and MeHg ranged 5.6–328.4 ng/g (wet weight) and 4.3–303.6 ng/g (wet weight) in aquatic products, respectively, and were very variable among species and origin sources. Target hazard quotient (THQ) suggested that MeHg exposure via consumption posed high health risks to children aged 2–7 and higher income families. Residents above the age of 13 and with low income have relatively lower health risk of MeHg exposure. Health impacts on heart attacks and newborns’ IQ from MeHg exposure were evaluated using dose-response relationships. Results showed that mother’s consumption of aquatic products (at 6 ounce per day) may cause a loss of 0.38 IQ points for newborns. For non-pregnant, consumption of aquatic products may cause an increase rate of mortality and morbidity of heart attacks at 10.59 and 78.45 per 100,000 persons, respectively. The negative health impact of consuming seawater fish was higher than freshwater fish.
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WU, JIAN-MING, and 吳見明. "Internal dose assessment of 131I." Thesis, 1986. http://ndltd.ncl.edu.tw/handle/39089964204818330940.
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Chen, Wei-Lin, and 陳韋霖. "Effective Dose Evaluation for Digital Radiography and Establishment Real-time Dose assessment." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/05986398692320164913.
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Chao, Tsi-chian, and 趙自強. "Dose Assessment in X-ray Diagnostic Radiology." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/92018988800831801496.
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