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1
ACOSTA, PEREZ CLARICE de F. "Contribuição ao calculo do valor alfa no estudo de otimização da radioproteção." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11560.
Повний текст джерелаАнотація:
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
2
Brucoli, Matteo. "Total ionizing dose monitoring for mixed field environments." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS093/document.
Повний текст джерелаАнотація:
La mesure de la dose ionisante est aujourd'hui une tâche cruciale pour une large gamme d'applications fonctionnant dans des environnements de rayonnement sévères. Dans le contexte de l'amélioration de la luminosité du grand collisionneur de hadrons (LHC), la mesure des niveaux de rayonnement le long du complexe d'accélérateurs du CERN va devenir encore plus difficile. A cet effet, une connaissance plus détaillée du champ de rayonnement dans le tunnel de l'accélérateur et ses zones adjacentes devient nécessaire pour définir les exigences d'installation, de déplacement ou de blindage de l'électronique sensible au rayonnement. Dans l’objectif d’améliorer la mesure de la dose absorbée par les systèmes exposés au champ de rayonnement mixte généré par l’accélérateur, des investigations sur des nouveaux dosimètres ont été menées.Dans le cadre de cette recherche, deux dispositifs ont été étudiés et caractérisés pour être utilisés comme dosimètres et éventuellement pour compléter l'utilisation du dosimètre au silicium actuellement utilisé au CERN, à savoir le RADFET (RADiation-sensitive Field Effect Transistor) : un NMOS commercial et un ASIC (Application-specific Integrated Circuit) nommé FGDOS. Les dispositifs ont été sélectionnés selon deux approches opposées : d'une part, la réduction des coûts permettrait d'augmenter la densité des capteurs déployés. En conséquence directe, une carte des doses plus détaillée serait obtenue pour les grands systèmes distribués comme le LHC. D'autre part, la dosimétrie peut être améliorée en déployant des détecteurs plus sensibles, ce qui permettrait de mesurer la dose lorsque les niveaux sont trop faibles pour le RADFET. De plus, des capteurs à plus haute résolution permettraient de caractériser le champ de rayonnement dans un temps plus court, c'est-à-dire avec une luminosité intégrée plus faible.La première approche a été réalisée en recherchant des solutions alternatives basées sur des dispositifs COTS (Commercial Off-The-Shelf), qui réduiraient considérablement les coûts et garantiraient une disponibilité illimitée sur le marché. À cette fin, des recherches ont été menées sur un transistor NMOS discret commercial, qui s'est révélé très sensible au rayonnement.La nécessité d'améliorer la résolution de la mesure de dose a conduit à étudier le FGDOS, un dosimètre en silicium innovant à très haute sensibilité qui permet de détecter des doses extrêmement faibles.La calibration du transistor NMOS et du FGDOS a été effectuées en exposant les dosimètres à des rayons gamma. Leur réponse au rayonnement a été caractérisée en termes de linéarité, de variabilité d'un lot à l'autre et d'effet du débit de dose. L'influence de la température a été étudiée et une méthode pour compenser l'effet de la température a été développée et mise en œuvre.Le FGDOS étant un système sur puce (SoC) avec plusieurs caractéristiques qui font du dosimètre un système extrêmement flexible, la caractérisation de ses différents modes de fonctionnement (actif, passif et autonome) a été effectuée. Suite à la première caractérisation, des questions se sont posées concernant les mécanismes de dégradation de la sensibilité affectant le dosimètre. Pour étudier ce phénomène, des campagnes d’irradiations ont été effectuées avec une puce d'essai incorporant seulement le circuit sensible au rayonnement du FGDOS. L'analyse des expériences a permis de comprendre les processus responsables de la dégradation de la sensibilité, en séparant la contribution du transistor de lecture de celle du condensateur à grille flottante. Les résultats de cette étude nous ont amenés à envisager de nouvelles solutions de conception et des méthodes de compensation.L’aptitude du transistor NMOS et du FGDOS à mesurer la dose ionisante dans les champs de rayonnement mixtes produits par le complexe d’accélérateurs du CERN a été vérifiée à l’aide de test radiatifs accélérés effectués dans le centre de tests en champs mixte à haute énergie du CERN (CHARM)The Total Ionizing Dose (TID) monitoring is nowadays a crucial task for a wide range of applications running in harsh radiation environments. In view of the High-Luminosity upgrade for the Large Hadron Collider, the monitoring of radiation levels along the CERN’s accelerator complex will become even more challenging. To this extent, a more detailed knowledge of the radiation field in the accelerator tunnel and its adjacent areas becomes necessary to design installation, relocation or shielding requirements of electronics sensitive to radiation. Aiming to improve the monitoring of the TID delivered by the mixed radiation field generated within the accelerator system, investigations on new suitable dosimeters have been carried out.With this research, two devices have been studied and characterized to be employed as dosimeter and possibly to complete the use of the silicon sensor currently employed at CERN for TID monitoring, i.e. the RADiation-sensitive Field Effect Transistor (RADFET): a commercial NMOS, and an ASIC (Application-Specific Integrated Circuit) named FGDOS. The devices have been selected following two opposite approaches: on the one hand, reducing the costs would allow the density of the deployed sensors to increase. As a direct consequence, a more detailed dose map would be obtained for large distributed systems like the LHC. On the other hand, the radiation monitoring can be further improved by deploying more sensitive detectors, which would allow to measure the dose where the levels are too low for the RADFET. Moreover, sensors with higher resolution would permit the characterization of the radiation field in a shorter time, which means within a lower integrated luminosity.The first approach has been accomplished by searching for alternative solutions based on COTS (Commercial Off-The-Shelf) devices, which would significantly reduce the costs and guarantee unlimited availability on the market. For this aim, investigations on a commercial discrete NMOS transistor, which was found to be very sensitive to the radiation, has been carried out.The need for improving the resolution of TID monitoring led to investigate the FGDOS, which is an innovative silicon dosimeter with a very high sensitivity that permits to detect extremely low doses.The calibration of the NMOS and the FGDOS have been performed by exposing the dosimeters to γ-ray. Their radiation response has been characterized in terms of linearity, batch-to-batch variability, and dose rate effect. The influence of the temperature has been studied and a method to compensate the temperature effect has been developed and implemented.Being the FGDOS is a System-On-Chip with several features that make the dosimeter an extremely flexible system, the characterization of its operational modes (Active, Passive and Autonomous) have been performed. Following the first characterization, some questions arose concerning the sensitivity degradation mechanisms affecting the dosimeter. To investigate this phenomenon, radiation experiments were performed with a test chip embedding only the radiation sensitive circuit of the FGDOS. The analysis of the experiments allowed the understating of the processes responsible for the sensitivity degradation, by separating the contribution of the reading transistor and the floating gate capacitor. The results of this investigation led us to considerer new design solution and compensation methods.The suitability of the NMOS and the FGDOS for TID measurement in the mixed radiation field produced by the CERN’s accelerator complex has been verified by performing accelerated radiation tests at the Cern High energy AcceleRator Mixed field facility (CHARM). The consistency of both sensors with the RADFET measurement has been demonstrated. The high sensitivity of the FGDOS leads to a significant improvement in terms of TID measurement in mixed radiation fields with respect to the RadFET, especially for low radiation intensities
3
Chapple, Claire Louise. "The optimisation of radiation dose in paediatric radiology." Thesis, University of Newcastle Upon Tyne, 1998. http://hdl.handle.net/10443/497.
Повний текст джерелаАнотація:
The importance of monitoring, and where possible reducing, the level of radiation dose from diagnostic X-ray examinations has been recognised for many years and is becoming of increasing concern. Dose reduction is of particular concern in paediatric radiology, and there are specific problems associated with the monitoring and comparison of radiation doses to children. Any optimisation study relies on a framework of good dosimetry. Two techniques have been developed to improve the collection of patient dose data: the automation of survey techniques to increase the quantity of data collected; and a method of correcting for patient size which reduces one source of variability in the data. An optimisation strategy has been developed, consisting of theoretical simulations, experimental verification and clinical implementation. Monte Carlo techniques were used for the theoretical study, which investigated the effect of beam filtration on radiation dose and image quality for a wide range of parameters, specifically for a neonatal size phantom. Simulations included both radiography of bone in soft tissue and fluoroscopy of iodine and barium based contrast media. The results were assessed in terms of the beam spectra and the absorption and transmission characteristics of the phantom and image receptor. Experimental measurements of dose and contrast were made for a simple slab phantom corresponding to that simulated, and results showed good agreement with those predicted. A further set of experimental measurements were carried out using anthropomorphic phantoms in a clinical setting, which demonstrated how the theoretical predictions translated to clinical practice. A clinical trial of the use of a 0.1mm copper filter for fluoroscopic examinations of infants was performed, and the filter shown to give substantial dose reduction with no significant loss in image quality. Some general recommendations on dose quantities and the application of optimisation strategies to paediatric radiology have been made.
4
Poon, Emily Sau Chee. "Patient-specific dose calculation methods for high-dose-rate iridium-192 brachytherapy." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86632.
Повний текст джерелаАнотація:
In high-dose-rate iridium-192 brachytherapy, the radiation dose received by the patient is calculated according to the AAPM Task Group 43 (TG-43) formalism. This table-based dose superposition method uses dosimetry parameters derived with the radioactive iridium source centered in a water phantom. It neglects the dose perturbations caused by inhomogeneities, such as the patient anatomy, applicators, shielding, and radiographic contrast solution.In this work, we evaluated the dosimetric characteristics of a shielded rectal applicator with an endocavitary balloon injected with contrast solution. The dose distributions around this applicator were calculated by the GEANT4 Monte Carlo (MC) code and measured by ionization chamber and GAFCHROMIC EBT film. A patient-specific dose calculation study was then carried out for 40 rectal treatment plans. The PTRAN_CT MC code was used to calculate the dose based on computed tomography (CT) images. This study involved the development of BrachyGUI, an integrated treatment planning tool that can process DICOM-RT data and create PTRAN_CT input initialization files. BrachyGUI also comes with dose calculation and evaluation capabilities.
We proposed a novel scatter correction method to account for the reduction in backscatter radiation near tissue-air interfaces. The first step requires calculating the doses contributed by primary and scattered photons separately, assuming a full scatter environment. The scatter dose in the patient is subsequently adjusted using a factor derived by MC calculations, which depends on the distances between the point of interest, the iridium source, and the body contour. The method was validated for multicatheter breast brachytherapy, in which the target and skin doses for 18 patient plans agreed with PTRAN_CT calculations better than 1%.
Finally, we developed a CT-based analytical dose calculation method. It corrects for the photon attenuation and scatter based upon the radiological paths determined by ray tracing. The scatter dose is again adjusted using our scatter correction technique. The algorithm was tested using phantoms and actual patient plans for head-and-neck, esophagus, and MammoSite breast brachytherapy. Although the method fails to correct for the changes in lateral scatter introduced by inhomogeneities, it is a major improvement over TG-43 and is sufficiently fast for clinical use.
En curiethérapies à haut débit de dose, la dose aux patients est évaluée selon le protocole AAPM Task-Group 43 (TG43), qui utilise des paramètres dosimétriques obtenues avec une source dans l'eau. Cependant, le patient, l'applicateur et le contraste ont des propriétés radiologiques différentes de l'eau; ces inhomogénéités sont donc négligées dans TG43.
Dans ce travail, nous utilisons le programme Monte Carlo (MC) GEANT4 pour évaluer les propriétés dosimétriques d'un applicateur rectal muni d'un blindage radio-protecteur et d'un ballon intra-cavitaire. Ces résultats sont confirmés par des mesures d'une chambre d'ionisation et des films GAFCHROMIC EBT. Une étude des calculs de dose a été faite avec le programme PTRAN_CT avec l'aide des images scanner de 40 patients de cancer rectal. Ceci a conduit au développement de BrachyGUI, un programme de planification de curiethérapie, capable de traiter les données DICOM-RT des patients et générer les paramètres d'entrée pour PTRAN_CT. BrachyGUI dispose d'outils de calcul, d'extraction et d'analyse de dose.
Nous proposons une nouvelle méthode de calcul qui tient compte des effets de diffusion au voisinage des interfaces tissus-air. Cette méthode calcule séparément la dose due aux photons primaires et diffusés, ensuite la composante diffusée est ajustée par un paramètre extrait des calculs MC incluant les contours du patient, la source et sa position. Nos résultats s'accordent avec une incertitude inferieure à 1% avec les calculs de dose à la surface et dans la cible effectués avec PTRAN_CT pour 18 patients en curiethérapie du sein.
Enfin, nous avons conçu une méthode analytique de calcul de dose qui incorpore l'atténuation et la diffusion des photons, et qui est basée sur les chemins radiologiques déterminées par traçage des trajectoires. Cet algorithme est validé par l'utilisation de fantômes, des données de patients traités pour divers cancers (oesophage, tête et cou), et par la curiethérapie MammoSite du sein. Bien que cette méthode ne reproduise pas bien les diffusions latérales induites par les inhomogénéités, elle représente une amélioration majeure par-rapport-à TG43 et est rapide pour une implémentation clinique.
5
Tozer-Loft, Stephen M. "Dose volume analysis in brachytherapy and stereotactic radiosurgery." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366100.
Повний текст джерела
6
Swart, Gillian. "Measurement of absorbed dose for paediatric patients for the purpose of developing dose guidelines in paediatric radiology." Thesis, Peninsula Technikon, 2004. http://hdl.handle.net/20.500.11838/1546.
Повний текст джерелаАнотація:
Thesis (MTech (Radiography))--Peninsula Technikon, 2004The radiation risks associated with children are higher than the risk for adults. Children have growing organs and they have a longer life expectancy than that of adults. As a consequence the effects of damage from radiation could be greater than in adults. Children who receive radiation damage may pass genetic damage onto future generations. This study was carried out to investigate the optimal effective x-ray dose young children need to receive who have radiographic examination to the chest at Tygerberg Hospital, South Africa. Chest radiographs are documented as being the most common radiographic examination done on children. The age groups of children participating in this study were 0-1 year, 1-5 years and 5-10 years. A total of 67 children were involved and the absorbed doses for 134 views of the anterior-posteria (AP) chest and lateral chest were measured. Entrance surface dose (ESD) values were determined, and measured mean ESD (mGy) and the ESD range was reported for each age group. This was done by attaching thermolurninescent dosirneters (TLD pellets) to the patients skin at the entrance point of the x-ray beam. The results were compared to similar studies done in Ireland and Nigeria From the ESD values obtained the absorbed doses ofthe eyes, heart, liver, thyroid and genitals could be calculated by using the "Childdose" programme ofthe NRPB. The ESD dose levels for South Africa compare favourably with Ireland. However the Nigerian values differed greatly from those of Ireland and South Africa It was very encouraging to note the comparative results achieved at Tygerberg Hospital especially due to the fact that this was the first time such study had been conducted in the Tygerberg Hospital Radiology Department. The results also compare favourable with that achieved by a group working in the United Kingdom. This group does similar surveys every five years as part of their radiation protection programme. The results were also in line with the UNSCEAR document of2000. v This study could serve as a valuable source of reference to radiographers and radiologists when performing paediatric radiology especially as the radiation absorbed dose could be used as a baseline to create awareness of size of dose received, and to limit deleterious radiation doses to patients and to prevent unnecessary exposures. A second significant outcome of the study was the effect that added filters had on the x-ray beam generated. Experiments were done in which the filtration filters were added sequentially. It was found that if the filtration was increased to 2mmAl the dose to the patient decreased by more than 20%. At 50 and 60 kV the density of the x-ray image on film only increased by 2%. From these results it may be concluded that an increase in filtration thickness used for paediatric chest x-rays should be giVIng reduced dose readings and assisting with radiation protection ofthe patient.
7
Shah, Nihal. "The investigation of low dose radiation hypersensitivity." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405748.
Повний текст джерела
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Wong, Tony Po Yin, and tony wong@swedish org. "Improving Treatment Dose Accuracy in Radiation Therapy." RMIT University. Applied Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080104.144139.
Повний текст джерелаАнотація:
The thesis aims to improve treatment dose accuracy in brachytherapy using a high dose rate (HDR) Ir-192 stepping source and in external beam therapy using intensity modulated radiation therapy (IMRT). For HDR brachytherapy, this has been achieved by investigating dose errors in the near field and the transit dose of the HDR brachytherapy stepping source. For IMRT, this study investigates the volume effect of detectors in the dosimetry of small fields, and the clinical implementation and dosimetric verification of a 6MV photon beam for IMRT. For the study of dose errors in the near field of an HDR brachytherapy stepping source, the dose rate at point P at 0.25 cm in water from the transverse bisector of a straight catheter was calculated with Monte Carlo code MCNP 4.A. The Monte Carlo (MC) results were used to compare with the results calculated with the Nucletron Brachytherapy Planning System (BPS) formalism. Using the MC calculated radial dose function and anisotropy function with the BPS formalism, 1% dose calculation accuracy can be achieved even in the near field with negligible extra demand on computation time. A video method was used to analyse the entrance, exit and the inter-dwell transit speed of the HDR stepping source for different path lengths and step sizes ranging from 2.5 mm to 995 mm. The transit speeds were found to be ranging from 54 to 467 mm/s. The results also show that the manufacturer has attempted to compensate for the effects of inter-dwell transit dose by reducing the actual dwell time of the source. A well-type chamber was used to determine the transit doses. Most of the measured dose differences between stationary and stationary plus inter-dwell source movement were within 2%. The small-field dosimetry study investigates the effect of detector size in the dosimetry of small fields and steep dose gradients with a particular emphasis on IMRT measurements. Due to the finite size of the detector, local discrepancies of more than 10 % are found between calculated cross profiles of intensity modulated beams and intensity modulated profiles measured with film. A method to correct for the spatial response of finite sized detectors and to obtain the
9
McFadden, Sonyia Lorraine. "Radiation dose optimisation in paediatric interventional cardiology." Thesis, University of Ulster, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516452.
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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/.
Повний текст джерелаАнотація:
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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Alvarez, Luis Emilio. "Radiation dose to the global flying population." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103443.
Повний текст джерелаАнотація:
Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 57-60).
Civil airliner passengers and crew are exposed to elevated levels of radiation relative to being at sea level. Previous studies have assessed the radiation dose received in particular cases or for cohort studies. Here we present the first estimate of the total radiation dose received by the worldwide civilian flying population. We simulated flights globally from 2000 to 2013 using schedule data, applying a radiation propagation code to estimate the dose associated with each flight. Passengers flying in Europe and North America exceed the International Commission on Radiological Protection (ICRP) annual dose limits at an annual average of 510 or 420 flight hours per year, respectively. However, this falls to 160 or 120 hours on specific routes under maximum exposure conditions.
by Luis Emilio Alvarez.
S.M.
12
Finklea, Lauren. "Room radiation dose coefficients for external exposure." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53943.
Повний текст джерелаАнотація:
In instances where a building room is radiologically contaminated, dose rate coefficients are needed to estimate the dose rate to the occupants. One’s position in the room, whether in the center of the room or the corner, could have an effect on dose rate. The Environmental Protection Agency (EPA) published in Federal Guidance Report 12 (EPA 1993) dose rate coefficients for idealized exposure geometries, including exposure to radionuclides distributed infinitely in various thicknesses of soil. The dimensions of the exposure plane were taken to be infinite in extent. Due to this assumption, using the Federal Guidance Report coefficients could lead to an incorrect estimate of dose rate inside a contaminated room. In order to apply the published coefficients for a structure, we developed Room Ratios using MCNP5 to compare air kerma rate of various room sizes and multiple building materials to the published infinite air kerma rate taking into account several receptor positions. Room Ratio values will be used for preliminary remediation risk assessment for environmental radionuclide clean up and be integrated into existing online tools and databases (epa-bprg.ornl.gov). The incorporation of ratios into these tools will update dose coefficients that previously accounted only for surface contamination (Eckerman 2010). Additionally, Room Ratios will allow Federal Guidance Report 12 dose coefficients application to customizable building materials and thickness.
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Akisheva, Yulia, and Ramin Farid. "Radiation Dose Analysis of the MIST Satellite." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-200617.
Повний текст джерела
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Nocum, Don. "Optimising patient radiation dose for uterine artery embolisation." Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29778.
Повний текст джерелаАнотація:
Uterine artery embolisation (UAE) is a minimally invasive procedure used to treat patients with symptomatic uterine fibroids and/or adenomyosis. UAE involves x-ray imaging with an angiography system that emits ionising radiation. The practices of radiation dose optimisation are critical for UAE patients who are usually in their reproductive-age – to minimise the exposure to reproductive organs.
The aims of this thesis were to: conduct a literature review on the factors that contribute to the radiation dose of patients during UAE; establish a regression model to identify the predictors of radiation dose at our centre using baseline UAE prospective data; to introduce a continuous quality improvement (CQI) program for UAE radiation dose optimisation and assess its impact on dose reduction and image quality; and to establish a new regression model to identify new UAE dose predictors on an upgraded angiography system.
The first study concluded that the regression model formed from a high volume of baseline data had the potential to improve practice and reduce UAE radiation dose. The second study concluded that the CQI program, which used theoretical and empirical evidence, had optimised UAE radiation dose practices, where dose reduction demonstrated no detrimental effects on image quality. The third study concluded that significant dose reductions between an upgraded and preceding angiography system were achieved, and the resultant multivariable linear regression (MLR) model can be used in future UAE procedures to validate its system-dependent nature.
The next logical step in future studies influenced by this thesis is the continual exploration of radiation dosimetry for UAE, with technological advancements and the calculation of effective dose for the ovaries and uterus. Understanding the risks, benefits and outcomes from this procedure, compared to surgery, can contribute to the decision making of patients, doctors and policy makers.
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MOURA, EDUARDO S. "Desenvolvimento de um objeto simulador para investigação de heterogeneidades em braquiterapia de alta taxa de dose." reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23889.
Повний текст джерелаАнотація:
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-08-07T14:35:13Z
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
16
Veinot, Kenneth Guy. "An angular dependent neutron effective-dose-equivalent dosimeter." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17595.
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Harris, Rhodri. "Radiation effects on custom MOS devices." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301376.
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Fricker, Katherine. "Collateral exposure: the additional dose from radiation treatment." Thesis, University of Canterbury. Physics and Astronomy, 2012. http://hdl.handle.net/10092/10361.
Повний текст джерелаАнотація:
For patients receiving radiation therapy, there is a risk of developing radiation induced carcinomas, especially if they have a long life expectancy. However, radiotherapy is not the only contributor of radiation exposure to healthy tissue. With the introduction of highly conformal treatment techniques comes the increase in pretreatment imaging necessary to accurately target tumour volumes and consequently, radiation exposure to healthy tissue.
In this work the radiation dose delivered to radiosensitive organs from a number of treatment planning techniques was evaluated and the risk of radiation induced cancer was assessed. MOSFET detectors and Gafchromic film were used to measure the accumulative concomitant dose to the thyroid and contralateral breast from early stage breast carcinoma
radiotherapy and to the contralateral testis from seminoma radiotherapy, with dose contributions from CT imaging for treatment planning, pretreatment imaging (CBCT) and treatment
delivery peripheral dose. To the author's knowledge this is the first work investigating the total concomitant treatment related dose and associated risk to these treatment sites.
Peripheral dose contributed the largest concomitant dose to the healthy tissue, measuring up to 0.7, 1.0 and 5.0 Gy to the testis, thyroid and contralateral breast, respectively. The
highest testicular, thyroid and contralateral breast carcinoma risk was found to be 0.4, 0.2 and 1.4%, respectively.
In conclusion, the risk of radiation induced carcinoma to the assessed radiosensitive tissues was found to be minimal, however, when considering treatment techniques and/or
introducing pretreatment imaging protocols, the dose to the normal tissue should be kept as low as reasonably achievable.
19
Aguwa, Kasarachi. "Radiation Dose Study in Nuclear Medicine Using GATE." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/593601.
Повний текст джерелаАнотація:
Dose as a result of radiation exposure is the notion generally used to disclose the imparted energy in a volume of tissue to a potential biological effect. The basic unit defined by the international system of units (SI system) is the radiation absorbed dose, which is expressed as the mean imparted energy in a mass element of the tissue known as "gray" (Gy) or J/kg. The procedure for ascertaining the absorbed dose is complicated since it involves the radiation transport of numerous types of charged particles and coupled photon interactions. The most precise method is to perform a full 3D Monte Carlo simulation of the radiation transport. There are various Monte Carlo toolkits that have tool compartments for dose calculations and measurements. The dose studies in this thesis were performed using the GEANT4 Application for Emission Tomography (GATE) software (Janet al., 2011) GATE simulation toolkit has been used extensively in the medical imaging community, due to the fact that it uses the full capabilities of GEANT4. It also utilizes an easy to-learn GATE macro language, which is more accessible than learning the GEANT4/C++ programming language. This work combines GATE with digital phantoms generated using the NCAT (NURBS-based cardiac-torso phantom) toolkit (Segars et al., 2004) to allow efficient and effective estimation of 3D radiation dose maps. The GATE simulation tool has developed into a beneficial tool for Monte Carlo simulations involving both radiotherapy and imaging experiments. This work will present an overview of absorbed dose of common radionuclides used in nuclear medicine and serve as a guide to a user who is setting up a GATE simulation for a PET and SPECT study.
20
Dahlman, Pär. "CT Urography : Efforts to Reduce the Radiation Dose." Doctoral thesis, Uppsala universitet, Enheten för radiologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-146332.
Повний текст джерелаАнотація:
Computed tomography urography (CTU) is today the imaging method used to investigate patients with suspected urinary tract malignancy, replacing the old imaging method intravenous pyelography (IVP) about a decade ago. The downside of this shift was that the effective radiation dose to the examined patient was eight times higher for CTU compared to IVP. Based on four different studies, the present thesis focused on efforts to reduce the CTU radiation dose. In study I, the number of cysts and solid lesions in the separate scan phases was evaluated in 57 patients undergoing four-phase CTU 1997-98. The number of scans was reduced from four to three when the nephrographic scan was abolished following study I. Study II registered the diameter of renal cell carcinoma (RCC) and the presenting symptoms in the total number of patients (n=232) diagnosed with RCC between 1997 and 2003. The results from study II showed that the critical size for RCCs to cause macroscopic hematuria was ≥ 4 cm. Study III was a dose-escalation study aimed to decide the minimal possible tube load in the unenhanced and excretory phase scans if the low dose images are reviewed together with normal dose corticomedullary phase images. Study III showed that it is possible to reduce the mean effective dose in three phase CTU from 16.2 mSv to 9.4 mSv with a combined low and normal dose CTU protocol. Study IV investigated the changes in the CTU protocol between 1997 and 2008, and the development of the effective radiation dose. Study IV clarified how the CTU protocol has changed between 1997 and 2008 and as a result the mean effective radiation dose to patients undergoing CTU in 2008 is only 39% of the effective dose in 1997. In conclusion, the findings from the studies included in this thesis have contributed to a reduced radiation dose to patients undergoing CTU. The mean effective dose from CTU is at present only three times higher compared to that from the IVP.
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Nord, Janne. "Modeling of high-dose radiation damage in semiconductors." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/nord/.
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Bero, Mamdouh A. "Development of a three-dimensional radiation dosimetry system." Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/719/.
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GERULIS, EDUARDO. "Controle de dose em transporte rodoviário de material radioativo." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10594.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Zaytzev, A. S., and A. V. Kutsak. "The radiation exposure to people due to natural radiation in buildings." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/54196.
Повний текст джерелаАнотація:
Research goals and objectives: To perform the research on the territory Zaporozhye region to identify the existing level of gamma background at the open area and inside the living buildings, and to estimate possible doses of radiation from the natural sources.
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Renaud, Marc-André. "Pre-calculated track Monte Carlo dose calculation engine." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121295.
Повний текст джерелаАнотація:
Modern treatment planning techniques such as inverse planning have increased the demand for rapid dose calculation methods to accommodate the large number of dose distributions required to generate a treatment plan. General-purpose Monte Carlo approaches for dose calculation are known to offer the highest accuracy in dose calculation at the expense of significant computing time. This work adapts a Macro Monte Carlo approach to dose calculation for electrons andprotons for use with a GPU card, using pre-generated tracks from general-purpose Monte Carlo codes. The algorithm was implemented on the CUDA framework for parallel programming on graphics cards. Comparisons of the algorithm inhomogeneous and inhomogeneous geometry with benchmark Monte Carlo codes yielded agreements within 1% in dose regions of at least 50% of Dmax and up to 3% in low dose regions. A Bragg peak positioning error of less than 1 mm was also observed. Additionally, the limited memory available in commercial graphics cards was overcome by subdividing a mother track bank residing on CPU memory into smaller samples of unique tracks. A method to quantify the latent uncertainty in dose values due to the limited size of a pre-generated track bank was developed. It was shown that the latent uncertainty follows a Poisson distribution as a function of the total number of unique tracks in the track bank. The implementation of the algorithm was found to transport particles in sub-second times per million history for every situation simulated, with speed-ups of 500-2600x for electrons over DOSXYZnrc and 2600-11500x for protons over GEANT4 depending on the particle energies and simulation media.Les techniques modernes de planification de traitement, telle que la planification inverse, ont augmenté la demande pour des méthodes rapides de calcul de dose pour accomoder le grand nombre de distributions de dose requises pour générer un plan de traitement. Les approches Monte Carlo d'usage général sont réputées pour offrir la plus haute précision au calcul de dose au détriment d'une demande plus élevée en temps de calcul. Cet oeuvre revisite une approche MonteCarlo macroscopique pour le calcul de dose avec électrons et protons en utilisant des traques pré-calculées à l'aide de codes Monte Carlo d'usage général. L'approche a été mise en oeuvre avec la plate-forme de programmation CUDA pour le programmage parallèle sur cartes graphiques. Des comparaisons de l'algorithme dans des phantômes homogènes et hétérogènes contre des codes Monte Carlo de référence ont démontré un accord de 1% et 1 mm ou mieux. En outre, les problèmes associés à la basse mémoire disponible dans les cartes graphiques commercial ont été surmontés à l'aide de la méthode de banque mère de traques pré-calculés. Une méthode pour quantifier l'incertitude latente dans les valeurs de dose dû au nombre limité de traques uniques dans la banque de traques a été développée. L'incertitude latente calculée suit une distribution de Poisson en fonction du nombre total de traques unique dans la banque de traques. Finalement, l'algorithme transporte tous les particules en moins d'une seconde pour chaque millions d'historiques dans chaque situation simulée. Un facteur d'accélération de 500-2600x pour le transport d'électrons comparé à DOSXYZnrc et 2600-11500x pour les protons comparé à GEANT4 a été observé, dépendamment de l'énergie des particules et de l'environnement dans lequel les particules sont transportées.
26
Peet, Samuel. "Out-of-field dosimetry in contemporary radiation therapy." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/234916/1/9325565_samuel_peet_thesis.pdf.
Повний текст джерелаАнотація:
Radiation therapy is a beneficial treatment for approximately half of all people diagnosed with cancer. This project improved the safety of radiation therapy for several vulnerable cohorts: pregnant patients, patients with electronic implants such as pacemakers, and young people at risk of developing secondary cancers later in life. In doing so, this research furthered equitable access to safe, high-quality health care.
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ANGELOCCI, LUCAS V. "Estudo de casos clínicos em radioterapia através do sistema de planejamento AMIGOBrachy." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26926.
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O sucesso de uma radioterapia depende do correto planejamento da dose a ser entregue ao volume alvo. Na braquiterapia, modalidade da radioterapia onde um radioisótopo selado é implantado intracavitariamente ou intersticialmente no paciente, há menos avanços em sistemas de planejamento de tratamento computacionais do que na teleterapia, amplamente mais utilizada nos serviços típicos. Porém, a braquiterapia, quando aplicável, é preferível por poupar tecidos sadios vizinhos de uma dose desnecessária. O AMIGOBrachy, um sistema de planejamento para braquiterapia de interface amigável, compatibilidade com outros sistemas comerciais em uso e integrado ao código MCNP6 (Monte Carlo N-Particle Transport Code v. 6) foi desenvolvido no Centro de Engenharia Nuclear do Instituto de Pesquisas Energéticas e Nucleares (CEN-IPEN) e atualmente está em processo de validação. Este trabalho contribuiu para este processo, avaliando três diferentes casos clínicos através do AMIGOBrachy com o formalismo do TG43 da AAPM (Associação Americana de Física Médica), protocolo que rege a dosimetria em braquiterapia, e comparando seus resultados com as distribuições de dose calculadas por outros sistemas comerciais consagrados: Varian BrachyVision TM (Varian Medical Systems; Palo Alto, CA, EUA) e Nucletron Oncentra® (Elekta; Estocolmo, Suécia). Os resultados obtidos estão dentro de uma faixa de concordância de ±10%, estando mais discrepantes em regiões muito próximas do aplicador, onde os sistemas de planejamento comerciais e o AMIGOBrachy divergem devido aos diferentes métodos de cálculo. Em pelo menos dois terços da região de interesse, porém, a dose concordou em uma faixa de ±3% para os três casos. Também foram realizadas simulações utilizando o formalismo do TG186 da AAPM, que considera heterogeneidades no tecido, para avaliar o impacto dos mesmos na dose. Em adição ao processo de validação, também foi realizado um estudo em braquiterapia oftálmica para posterior inserção de um módulo adicional ao AMIGOBrachy; para isso, um modelo de olho humano foi desenvolvido utilizando geometria UM (Unstructured Mesh), para validação com o código MCNP6, que apenas nesta versão demonstra um novo recurso capaz de simular uma geometria híbrida: parcialmente analítica, parcialmente UM. O modelo considera dez diferentes estruturas no olho humano: esclera, coroide, retina, corpo vítreo, córnea, câmara anterior, lente, nervo óptico, parede do nervo óptico, e um tumor definido de forma arbitrária crescendo da superfície externa do globo ocular em direção ao seu centro. Os resultados foram comparados com um modelo de olho puramente analítico modelado com o MCNP6 e tomado como referência. Os resultados foram satisfatórios em todas as simulações desenvolvidas, exceto para as estruturas do nervo óptico e sua parede, que devido ao seu pequeno tamanho e distância da fonte, mostraram erros relativos maiores, mas ainda menores que 10%, e não representam problema de preocupação clínica uma vez que recebem doses muito pequenas. Discutiu-se também a eficácia e problemas encontrados nessa nova capacidade do código MCNP de simular geometrias híbridas, uma vez que é recente e ainda apresenta deficiências, que tiveram que ser contornadas no presente trabalho.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
28
Rowbottom, Carl Graham. "Optimisation of beam-orientations in conformal radiotherapy treatment planning." Thesis, Institute of Cancer Research (University Of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314088.
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Tangboonduangjit, Puangpen. "Intensity-modulated radiation therapy dose maps the matchline effect /." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060724.095712/index.html.
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30
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.
Повний текст джерелаАнотація:
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]
31
Wiklund, Kristin. "Modeling of dose and sensitivity heterogeneities in radiation therapy." Doctoral thesis, Stockholms universitet, Fysikum, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-74719.
Повний текст джерелаАнотація:
The increased interest in the use of light ion therapy is due to the high dose conformity to the target and the dense energy deposition along the tracks resulting in increased relative biological effectiveness compared to conventional radiation therapy. In spite of the good clinical experience, fundamental research on the characteristics of the ion beams is still needed in order to be able to fully explore their use. Therefore, a Monte Carlo track structure code, KITrack, simulating the transport of electrons in liquid water, has been developed and used for calculation of parameters of interest for beam characterization. The influence of the choice of the cross sections for the physical processes on the electron tracks has also been explored. As an alternative to Monte Carlo calculations a semi-analytical approach to calculate the radial dose distribution from ions, has been derived and validated. In advanced radiation therapy, accurate characterization of the beams has to be complemented by comprehensive radiobiological models, which relate the dose deposition into the cells to the outcome of the treatment. The second part of the study has therefore explored the influence of heterogeneity in the dose deposition into the cells as well as the heterogeneity in the cells sensitivity to radiation on the probability of controlling the tumor. Analytical expressions for tumor control probability including heterogeneous dose depositions or variation of radiation sensitivity of cells and tumors have been derived and validated with numerical simulations. The more realistic case of a combination of these effects has also been explored through numerical simulations. The MC code KITrack has evolved into an extremely useful tool for beam characterization. The tumor control probability, given by the analytical derived expression, can help improve radiation therapy. A novel anisotropy index has been proposed. It is a measure of the absence of isotropy and provides deeper understanding of the relationship between beam quality and biological effects.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.
32
Castellano, I. A. "Optimisation of radiation dose to patients in computed tomography." Thesis, Institute of Cancer Research (University Of London), 2006. http://publications.icr.ac.uk/9716/.
Повний текст джерелаАнотація:
Methodologies for optimisng CT scanning protocols have been developed in this project. In the first instance, a novel Monte Carlo CT model has been constructed to calculate effective dose. Comparisons With experimental data in CT dose phantoms indicate that the accuracy of the model is better than 10%. The model has been used to demonstrate that, if used with care, commercial dosimetry packages can calculate effective dose to standard sized subjects undergoing multi-slice CT scans of the torso without incurring errors larger than 20 %. For electron-beam CT, the model has been used to calculate effective doses for screening and diagnostic scans; it has also demonstrated that commercial packages are still valid except for scans of the thorax, where a correction factor of 0.75 should be applied. In the second instance, an optimisation methodology, based on phantom experiments to evaluate image quality and the novel Monte Carlo CT model to calculate patient doses, has been devised. It has been applied to scans of the paediatric abdomen and pelvis. If the noise levels observed in adult scanning are maintained across all patient sizes, there is a potential for dose reduction in paediatric scanning by a factor of 3-6 compared to local clinical practice. The tube voltage can be reduced to increase the visualisation of iodine-enhanced tissue and visceral fat. The optimisation methodology has also been applied to CT perfusion of the head and neck where a risk of skin radiation injury exists. A scan protocol has been recommended and implemented in a patient trial. It increases by 10 % the contrast-to-noise ratio of iodine-enhanced tissues achievable with the manufacturer's recommended protocol and delivers half the surface dose to the patient with no detrimental effect on normal perfusion parameters.
33
Raines, Katherine Elizabeth. "The effects of chronic low-dose radiation on bumblebees." Thesis, University of Stirling, 2018. http://hdl.handle.net/1893/28699.
Повний текст джерелаАнотація:
The consequences to wildlife of living in contaminated areas with chronic low-dose rates of radiation are still relatively unknown. Laboratory studies using acute radiation have demonstrated that invertebrates are relatively radioresistant compared to other taxa. However, there is little scientific evidence to show how chronic low dose rates affect invertebrates. This is problematic for understanding the consequences to wildlife living in highly contaminated areas and also testing assumptions made for invertebrates by the International Commission on Radiological Protection (ICRP). This thesis was designed to address a number of recommendations have been suggested to improve radioecological studies and help reduce the uncertainty as to effects at low dose rates. These include environmentally relevant laboratory studies (Chapters 2 and 4), improved dosimetry and dose assessments (Chapter 3), investgating confounding factors (Chapter 4) and continuity between laboratory experiments and field work conducted in the Chernobyl Exclusion Zone (CEZ) (Chapter4). Chapter 2 presents an environmentally-relevant experiment testing how bumblebee reproduction and life history is affected by chronic low-dose rates. Unexpectedly, at dose rates equivalent to the CEZ, queen production declined and reproductive timing was altered. The estimation of dose rates to establish a dose-effect relationship for wild animals is difficult and a common criticism of radioecological studies, therefore, Chapter 3 tests whether the common approach to measuring only external ambient dose rates is suitable and whether the inclusion of life-history traits significantly alters the dose rate. The findings from this chapter reiterate the necessity to use dose-assessment tools to test different parameters to estimate dose rate in different scenarios to account for unknown variation. Chapter 4 demonstrates that in areas of elevated dose rates in the CEZ parasite burden was higher and bumblebees did not live as long. These results were reinforced by a laboratory study, which determined bumblebees exposed to increased radiation doses had high parasite burdens and were infected quicker, resulting in reduced longevity. The data in this thesis detected effects below the current dose bands used in international radioprotection and therefore advocate these dose bands be re-evaluated. However, the data do not support studies which have measured adverse effects at dose rates similar to background and suggest that confounding factors such as habitat quality and co-stressors need to be included in field and laboratory studies.
34
Hagelberg, Melker. "Minimization of radiation dose exposure during a PCI procedure." Thesis, KTH, Fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189149.
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Wooten, Hasani Omar. "Calculation of internal dose conversion factors for selected spallation products." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17247.
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36
Hearnsberger, David Wayne. "An external dose reconstruction involving a radiological dispersal device." Diss., Texas A&M University, 2006. http://hdl.handle.net/1969.1/4759.
Повний текст джерелаАнотація:
Recent events have underscored the need for the United States government to provide streamlined emergency response procedures and subsequent dose estimations for personnel responding to incidents involving radioactive material. Indeed, the National Council on Radiation Protection and Measurements Report No. 138 (NCRP 2001) indicates that exposures received by first responders will be important for a number of reasons, including planning for the appropriate use of key personnel in an extended emergency situation. In response, the Department of Homeland Security has published Protective Action Guides (DHS 2006) to help minimize these exposures and associated risks. This research attempts to provide some additional radiological exposure knowledge so that an Incident Commander, with limited or no information, can make more informed decisions about evacuation, sheltering-in-place, relocation of the public, turn-back levels, defining radiation hazard boundaries, and in-field radiological dose assessments of the radiation workers, responders, and members of the public. A method to provide such insight begins with providing a model that describes the physics of radiation interactions, radiation source and geometry, collection of field measurements, and interpretation of the collected data. A Monte Carlo simulation of the model is performed so that calculated results can be compared to measured values. The results of this investigation indicate that measured organ absorbed doses inside a tissue equivalent phantom compared favorably to the derived organ absorbed doses measured by the Panasonic thermoluminescence dosimeters and with Monte Carlo âÂÂNâ Particle modeled results. Additionally, a Victoreen 450P pressurized ion chamber measured the integrated dose and these results compared well with the Panasonic right lateral TLD. This comparison indicates that the Victoreen 450P ionization chamber could potentially serve as an estimator of real-time effective dose and organ absorbed dose, if energy and angular dependence corrections could be taken into account. Finally, the data obtained in this investigation indicate that the MCNP model provided a reasonable method to determine organ absorbed dose and effective dose of a simulated Radiological Dispersal Device in an Inferior-Superior geometry with Na99mTcO4 as the source of radioactive material.
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Madhoo, Jitesh. "Continuous low dose rate irradiation of the rat brain." Doctoral thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/26785.
Повний текст джерелаАнотація:
The reported median survival time for patients who are diagnosed with high grade astrocytomas and who undergo postoperative radiotherapy is of the order of 24 to 40 weeks. The course of radiotherapy administered to these patients takes up a considerable portion of their expected survival time. Therefore, any means of reducing the treatment time may contribute to an enhanced quality of life for these patients. A potentially useful method for the reduction of the treatment time may be achieved with the use of continuous low dose rate external beam radiotherapy, where the treatment is administered over a 12 to 24 hour period. A relationship between fractionated and continuous low dose rate irradiation has been reported for skin, however, no such relationship has been reported for the brain. Low dose rate protocols that are equivalent in effect to fractionated (conventional) protocols can be derived using the linear quadratic theory, provided that quantitative radiobiological data for normal tissue (brain) is known. Thus, the aim of the current study is to test the radiation tolerance of the rat brain to low dose rate and fractionated radiation in order to establish the values for the parameters of the linear quadratic model.
38
Rossouw, Maria Susanna. "Validation of endpoints as biomarkers of low-dose radiation damage." Thesis, Cape Technikon, 2004. http://hdl.handle.net/20.500.11838/1461.
Повний текст джерелаАнотація:
Thesis (MTech (Biomedical Technology))--Cape Technikon, Cape Town, 2004The need for radiobiological research was bom from the discovery that high doses of radiation could cause cancer and other health effects. However, recent developments in molecular biology uncovered the effects of low doses of radiation on different biological systems and as a result new techniques have been developed to measure these effects. The aim of this study was thus to validate biomarkers of initial DNA strand breaks, micronucleus formation, and the different pt ;ases of apoptosis as biological indicators of low-dose radiation damage. Furthermore, the difference in response of blood cells to different qualities and doses of radiation was investigated by irradiating cells with low- and high-LET radiation simultaneously. Blood from one donor was irradiated with doses between 0 and 4 Gy gamma- and neutron radiation. The alkaline single-cell gel electrophoresis (comet) assay was performed on different cell preparations directly after irradiation for the detection of initial DNA strand breaks. Radiation-induced cytogenetic damage was investigated using the cytokinesis-blocked micronucleus assay while different features of apoptosis were investigated by measuring caspase activation, enzymatic DNA fragmentation, and cellular morphology. The comet assay was sensitive enough to detect DNA strand breaks above 0.25 Gy and showed that the Iymphocyte isolation process induced some endogenous damage in cells, detected by the formation of highly damaged cells and hedgehogs in isolated cell preparations only.
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Saukko, E. (Ekaterina). "Medical use of radiation in gastroenterology:optimising patient radiation exposure during endoscopic retrograde cholangiopancreatography (ERCP)." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526221083.
Повний текст джерелаАнотація:
Abstract Fluoroscopically guided procedures are currently an area of special concern in relation to radiation protection, as they may produce a high radiation dose to patients and increase the risk of skin injury. ERCP is a gastrointestinal procedure used as a gold standard in the treatment of pancreatobiliary disorders. It is performed under endoscopic and fluoroscopic guidance. Recently, both the number and the complexity with associated increased technical difficulty of therapeutic ERCP procedures have significantly increased. The present study aimed to assess the medical use of radiation in ERCP, with special emphasis on optimisation of radiation protection of patients. For this purpose, the level of patient radiation exposure during ERCP was evaluated by registering the radiation dose indices in Finnish hospitals. The entrance surface dose was measured by thermoluminescent dosimeters and the effective dose was estimated using conversion coefficients. For dose optimisation and for quality assurance, the local diagnostic reference levels (DRL) for ERCP were established and reviewed after five years. A single centre prospective analysis was conducted to identify patient-, procedure- and operator-related factors affecting dose area product (DAP) and fluoroscopy time (FT). The results showed a large variation of dose indices in overall, as among participating hospitals due to differences in patient characteristics, operator, equipment and procedural complexity. The risk of radiation-induced skin injury and the lifetime cancer risk seems to be reasonably low, indicating ERCP to be a low-dose study. Local DRL is an effective tool in the optimisation process, as a certain degree of dose reduction was achieved during the years. Multiple factors were found to affect DAP and FT in ERCP. The awareness of these factors may help to predict possible prolonged procedures that cause a higher radiation dose to the patient and thus facilitate the use of appropriate precautionsTiivistelmä Säteilysuojelun näkökulmasta läpivalaisuohjauksessa tehtävät toimenpiteet ovat erityisen huolen aiheena, koska ne voivat aiheuttaa potilaille suuria säteilyannoksia ja siten lisätä ihovaurion riskiä. ERCP on ruoansulatuskanavan endoskopiatoimenpide, jota käytetään haima- ja sappitiesairauksien hoidossa kultaisena standardina. ERCP suoritetaan duodenoskoopilla läpivalaisukontrollissa. Viime vuosina ERCP toimenpiteiden määrät ja toimenpiteiden monimutkaisuus ovat kasvaneet merkittävästi lisääntyneen teknisen haastavuuden vuoksi. Tutkimuksen tarkoituksena oli arvioida säteilyn lääketieteellistä käyttöä ERCP:ssa, kiinnittäen eritystä huomiota potilaan säteilysuojelun optimointiin. Potilaan säteilyaltistuksen tasoa ERCP:ssa arvioitiin keräämällä potilasannoksia suomalaisista sairaaloista, pinta-annokset mitattiin termoloistedosimetreilla ja efektiivinen annos laskettiin muuntokertoimilla. Säteilyaltistuksen optimointi- ja laadunvalvonnan työkaluksi ERCP:lle asetettiin paikalliset vertailutasot ja ne tarkistettiin 5 vuoden kuluttua. Potilaaseen, toimenpiteeseen ja toimenpiteen suorittajaan liittyvät tekijät, jotka vaikuttavat annoksen ja pinta-alan tuloon (DAP) sekä läpivalaisuaikaan, selvitettiin retrospektiivisesti yhdessä sairaalassa. Tutkimuksen tulokset osoittivat, että potilaan säteilyannoksissa oli suurta vaihtelua niin yleisesti, kuin osallistuvien sairaaloiden välillä. Vaihtelu johtui potilaan ominaisuuksista, erilaisista läpivalaisulaitteista, toimenpiteen suorittajista ja ERCP toimenpiteiden vaikeusasteesta. Säteilyn aiheuttaman ihovaurion riski ja elinikäinen syöpäriski näyttäisi tulosten perusteella olevan kohtuullisen alhainen, mikä osoittaa, että ERCP on matala-annostutkimus. Paikallinen vertailutaso osoittautui tehokkaaksi optimointityökaluksi, sillä annostason lasku ERCP:ssa saavutettiin vuosien kuluessa. Useiden tekijöiden todettiin vaikuttavan DAP:n ja läpivalaisuaikaan ERCP:ssa. Näiden tekijöiden tiedostaminen voi auttaa tunnistamaan etukäteen ne haastavat ERCP toimenpiteet, jotka voivat aiheuttaa suuria säteilyannoksia potilaille, ja siten mahdollistaa niihin varautumisen
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Skiöld, Sara. "Radiation induced biomarkers of individual sensitivity to radiation therapy." Doctoral thesis, Stockholms universitet, Institutionen för molekylär biovetenskap, Wenner-Grens institut, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-97123.
Повний текст джерелаАнотація:
Fifty percent of solid cancers are treated with radiation therapy (RT). The dose used in RT is adjusted to the most sensitive individuals so that not more than 5% of the patients will have severe adverse healthy tissue effects. As a consequence, the majority of the patients will receive a suboptimal dose, as they would have tolerated a higher total dose and received a better tumor control. Thus, if RT could be individualized based on radiation sensitivity (RS), more patients would be cured and the most severe adverse reactions could be avoided. At present the mechanisms behind RS are not known. The long term aim of this thesis was to develop diagnostic tools to assess the individual RS of breast cancer patients and to better understand the mechanisms behind the RS and radiation effects after low dose exposures. The approach was based on the hypothesis that biomarkers of individual RS, in terms of acute adverse skin reactions after breast cancer RT, can be found in whole blood that has been stressed by low doses of ionizing radiation (IR). To reach this goal two different approaches to identify biomarkers of RS have been investigated. A protocol for the analysis of differential protein expression in response to low dose in vitro irradiated whole blood was developed (paper I). This protocol was then used to investigate the proteomic profile of radiation sensitive and normo-sensitive patients, using isotope-coded protein labeled proteomics (ICPL). The results from the ICPL study (paper III) show that the two patient groups have different protein expression profiles both at the basal level and after IR. In paper II the potential biomarker 8-oxo-dG was investigated in serum after IR. The relative levels of IR induced 8-oxo-dG from radiation sensitive patients differ significantly from normo-sensitive patients. This indicates that the sensitive patients differ in their cellular response to IR and that 8-oxo-dG is a potential biomarker for RS.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.
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Fenwick, John David. "Biological modelling of pelvic radiotherapy : potential gains from conformal techniques." Thesis, Institute of Cancer Research (University Of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322314.
Повний текст джерела
42
Brunet-Benkhoucha, Malik. "Tomosynthesis-based intraoperative dosimetry for low dose rate prostate brachytherapy." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32401.
Повний текст джерелаАнотація:
The aim of this study is to develop an intraoperative dose assessment procedure that can be performed after an I-125 prostate seed implantation, while the patient is still under anaesthesia. To accomplish this, we reconstruct the 3D position of each seed and co-register it with the prostate contour acquired with a transrectal ultrasound (TRUS) probe. Our seed detection method involves a tomosynthesis-based filtered reconstruction of the volume of interest requiring 7 projections acquired over an angle of 60o with an isocentric imaging system. The co-registration between the tomosynthesis-based seed positions and the TRUS-based prostate contour is based on the planned position. A phantom and a clinical study (25 patients) were carried out to validate the technique. In the patient study, the automatic tomosynthesis-based reconstruction yields a seed detection rate of 96.7% and less than 2.6% false-positive. The seed localization error obtained with a phantom study is 0.4 ± 0.4 mm. The co-registration method based on planned seed position has proved to be not accurate enough for dosimetric purposes. We believe that this technique may be used to discover considerable underdosage and to improve the dosimetric coverage by potentially reimplanting additional seeds.L'objectif de ce projet est de développer une procédure d'évaluation dosimétrique intra-opératoire en implantation prostatique de grains d'iode 125. Pour y arriver, la position 3D des grains doit être reconstruite et recalée avec les contours de la prostate imagée en échographie endorectale. La reconstruction des grains est basée sur une technique de tomosynthèse requérant 7 projections acquises entre -30o et 30o. Le recalage entre la position 3D des grains et les contours utilise comme cible la position planifiée des grains. Notre technique de reconstruction dosimétrique a été testée sur un mannequin et dans une étude clinique incluant 25 patients. Notre méthode permet de reconstruire la position 3D des grains avec une précision de 0.4 ± 0.4 mm. De plus, l'étude clinique a démontré un taux de détection de 96.7% des grains et incluant moins de 2.6% de faux-positifs. La méthode de recalage n'a pas permis d'atteindre une précision acceptable pour une application clinique. La technique développée permet de repérer la présence de sous-dosage considérable et ouvre la porte vers la réimplantation de grains additionnels afin d'améliorer la couverture dosimétrique de la prostate.
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POLI, MARIA E. R. "Definição do volume de planejamento do alvo (PTV) e seu efeito na radioterapia." reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11552.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Lampe, Nathanael. "De l’impact à long terme des radiations ionisantes sur les systèmes vivants." Thesis, Université Clermont Auvergne (2017-2020), 2017. http://www.theses.fr/2017CLFAC011/document.
Повний текст джерелаАнотація:
La vie sur Terre s’est adaptée à un environnement où il y a un faible et persistent bruit de fond radiatif qui interagit avec les cellules. Loin des effets clairement nocifs des radiations à haute dose, il est difficile d’évaluer et de comprendre les impacts des faibles doses de la radioactivité naturelle sur les systèmes vivants. Nous avons tenté d’étudier si le bruit de fond radiatif est un facteur important dans l’évolution, en menant des expériences évolutives identiques avec Escherichia coli au Laboratoire de Physique Corpusculaire de Clermont-Ferrand, et au Laboratoire Souterrain de Modane. Malgré une différence d’un facteur 7,3 entre les taux d’interaction des rayonnements ionisants avec les cellules dans les deux laboratoires, aucune différence significative n’a pu être trouvée dans le fitness compétitif des populations cellulaires évoluées dans chaque laboratoire. Par simulation, nous avons montré que le taux d’interaction entre le bruit de fond radiatif et E. coli est cent fois plus faible que le taux de mutations d’origine endémique, ce qui renforce l’hypothèse que les radiations naturelles ont peu d’effet sur l’évolution. Dans le cadre du projet Geant4-DNA, nous avons développé une application complète de simulation mécanistique des dommages radio-induits à l’ADN, afin d’explorer davantage cette hypothèse. Avec cette application, on a irradié un modèle du génome d’E. coli, montrant que pour l’irradiation par des électrons d’énergies > 10 keV, le rendement des cassures double brin est de 0,006 – 0,010 CDB Gy-1 Mbp-1, selon le modèle de piégeage des radicaux chimiques. Ce résultat est en accord avec des données expérimentales, et souligne plus encore que les radiations ionisantes d’origine naturelle n’ont qu’une contribution mineure aux mutations responsables de l’évolutionAll life on earth has adapted to an environment where there is a small, persistent, radiation background interacting with cells. Unlike evaluating the clearly harmful effects of high radiation doses, understanding the effects of this low persistent radiation dose on living systems is incredibly difficult. We have attempted to study whether background radiation is an important factor in evolution by conducting identical evolution experiments with Escherichia coli in the Clermont-Ferrand Particle Physics Laboratory and the Modane Underground Laboratory. Despite a 7.3 fold difference in the rate of interactions between the radiation background and cells between the two environments, no significant difference was found in the competitive fitness of the cell populations grown at each location. Using simulations, we showed that the rate at which ionising radiation interacts with cells is one hundred times less frequent than E. coli’s mutation rate in our experimental conditions, supporting the contention that natural radiation has no strong evolutionary effect. To further support this conclusion, we developed a mechanistic simulation for DNA damage as part of the Geant4-DNA project. Using this application, we irradiated a model of an E. coli genome, showing that for electron irradiation > 10 keV, the double strand break yield can be reasonably estimated to be between 0.006 – 0.010 DSB Gy-1 Mbp-1, depending upon the modelling of radical scavenging. This is in agreement with experimental data, further highlighting the small role natural ionising radation plays as a cause of mutations
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Ashton, Christopher D. "Total dose radiation test methodologies for advanced spacecraft electronics experiencing enhanced low dose rate sensitivity." Thesis, University of Surrey, 2016. http://epubs.surrey.ac.uk/810105/.
Повний текст джерелаАнотація:
The purpose of this thesis is to determine whether hydrogen can be implanted into elec- tronic components for the goal of investigating low ionising dose rate sensitivity, and using this to suggest whether hydrogen implantation can be used as an accelerated method to detect ELDRS (Enhanced Low Dose Rate Sensitivity) susceptability. Current ground testing methods for total ionising dose irradiate using cobalt-60 at dose rates greater than 10mGy(Si)/s up to 200Gy. It has been found that bipolar devices show an increased susceptibility to radiation induced damage at dose rates below 10mGy(Si)/s known as ELDRS. Current research has linked ELDRS susceptibility with hydrogen content within the integrated circuit and experiments based upon hydrogen soaking de-lidded bipolar devices demonstrate this relationship, however this has not led to an accepted method for testing ELDRS susceptibility in previously un-tested devices. In this thesis, a novel proposal is put forward whereby bipolar devices are directly implanted with hydrogen using a targeted ion beam in order to accelerate the testing process. Hydrogen implantation via a 600keV ion beam has been achieved to a level of 10^17 H/cm^2 in Analog Device’s AD590KF temperature transducer, and 10^14-15 H/cm^2in National Semiconductor’s LM124 quad operational amplifiers. Devices were decapped, optically analysed, and targeted with a focussed proton beam. These devices were then irradiated at 15mGy/s, 5mGy/s and 15mGy/s. Increased degradation was seen at lower dose rates which was matched by high dose rate irradiation of the implanted devices followed by a room temperature anneal. The use of ion implantation for the development of an accelerated ELDRS test method is proposed. This thesis demonstrated that hydrogen can be succesfully implanted into devices, established an upper bound for the LM124 for implantation and a lower bound for hydrogen remaining in the target area and the effect of hydrogen implantation on the AD590 temperature transducer is discussed. This thesis concludes by suggesting hydrogen implantation as a method for use by manufacturers during the design and investigation of intrinsically ELDRS-free technologies.
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Henriksson, Katja. "Strålskydd för nuklearmedicinsk personal som jobbar med Tc-99m: vikten av att använda blyförkläde, sprutskydd och distansverktyg." Thesis, Malmö universitet, Fakulteten för hälsa och samhälle (HS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-25533.
Повний текст джерелаАнотація:
Inom nuklearmedicin exponeras personal dagligen för joniserande strålning. Det kan vara både i form av en öppen strålkälla vid uppdrag av radiofarmaka och vid bildtagning där personalen hjälper och ger stöd till patienten som blivit injicerad. Vid uppdrag av radiofarmaka används strålskydd i form av sprutskydd och distansverktyg medan blyförkläde används vid kontakt med patienter. Dessa skydd är till för att minska skador som kan uppstå vid exponering. Den svenska strålsäkerhetsmyndigheten (SSM) har föreskrivit dosgränser som inte får överskridas för att minska risken för skador. Teknetium-99m (99mTc) är den vanligaste radionukliden inom den nuklearmedicinska verksamheten. Syftet med denna studie var att kartlägga strålningsexponeringen för personal som jobbar med 99mTc och på så sätt visa behovet av olika typer av strålskydd för att reducera stråldosen. I denna studie utfördes fingerdosmätningar vid uppdrag av 99mTc med hjälp av termoluminiscenta dosimetrar som placerades på de tre mest utsatta fingrarna, digitus I-III, bilateralt. Mätningarna genomfördes vid uppdrag utan strålskydd, med en pincett och med fullt strålskydd (sprutskydd samt två pincetter). Studien innefattar även stråldosmätningar med och utan blyförkläde för myokardscintigrafi, skelettscintigrafi och lungscintigrafi. Dessa mätningar utfördes med en direktavläsande personal electronic dosimeter (PED) där den effektiva dosen registrerades. Resultaten för fingerdosmätningarna visar en signifikant skillnad i stråldos beroende på om och vilket strålskydd som används. Högst dos fick de som drog upp helt utan strålskydd och vänster långfinger fick den högsta ekvivalenta dosen. För stråldosmätningarna med och utan blyförkläde utfördes ett Mann-Whitney U-test som visade ett p-värde på <0,05 vilket tyder på att det finns en statistisk signifikant skillnad. Högst effektiv dos uppmättes vid lungscintigrafi för personal som inte använde blyförkläde.Personnel working with radiopharmaceuticals in the nuclear medicine department are exposed to radiation on the daily basis. The source of radiation can both be open as in the withdrawal procedure and external as when the patient has been injected and ready for imaging. There are different types of radiation protection depending on which task that is performed. Syringe shielding and distance tools are used during the withdrawal and lead aprons are used when positioning the patient under the camera. The Swedish radiation safety authority (SSM) prescribe dose limits to reduce any risk of injury connected to radiation. These limits must not be exceeded. Technetium-99m (99mTc) is the most common radiopharmaceutical in the nuclear medicine department. The purpose of this study was to study the radiation exposure to personnel working with 99mTc and evaluate the need for radiation protection to reduce the radiation dose. This study includes measurement of the equivalent dose to the three most exposed fingers, digitus I-III bilateral, during the withdrawal of 99mTc. Thermoluminiscent dosimeters was used to detect radiation and was placed on top of the finger. The measurements were performed without radiation shielding, with only one tweezer as distance tool and with full radiation shielding (syringe shielding and two tweezers as distance tools). It also includes measurement of the effective dose during myocardial scintigraphy, bone scan and lung scintigraphy with or without lead apron. For these measurements a personal electronic dosimeter was used to detect radiation. The result of the finger doses showed a significant difference in radiation dose depending on which protection was used. The highest dose was recovered from not using any protection at all and the highest equivalent dose was obtained by left middle finger. For the measurement regarding the effective dose with or without lead apron a Mann-Whitney U-test was performed and showed a p-value of <0,05 which indicates a statistical significant difference. The highest effective dose was recovered from lung scintigraphy when the personnel was not wearing a lead apron.
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Ozols, Agris. "Low-dose studies of genomic instability-mechanisms and targets." Thesis, Queen Mary, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271260.
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48
Dong, Xiuqin. "Safety limit estimation for cataract induced by ultraviolet radiation /." Stockholm, 2005. http://diss.kib.ki.se/2005/91-7140-451-1/.
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RODRIGUES, DEMERVAL L. "Otimizacao no controle dos valores de radiacao nas dependencias do ciclotron de 30 MeV do IPEN." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11027.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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FERREIRA, DANILO C. "Desenvolvimento e calibração de um sistema dosimétrico de rotina em processamento por irradiação." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10593.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP