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Jardine, Paul. "Applications of gel based chemistry dosimetry." Thesis, Queensland University of Technology, 1994. https://eprints.qut.edu.au/37183/1/37183_Jardine_1994.pdf.
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The transformation of Fe2+ to Fe3+ ions in ferrous sulphate-agarose-xylenol orange (FAX) gel due to irradiation results in a change of absorbance in the FAX gel, which can then be used for the dosimetry of the x-ray beam. The project's aim was to investigate the performance of a laser based system that determines the dose distribution of an x-ray field by measuring the change in absorbance of the FAX gel due to irradiation.
Initially a one-dimensional laser scanning system was constructed to perform calibration tests on the FAX gel. Calibration curves were obtained at different x-ray energies (200 kVp, 300 kVp, 6 MV, 10 MV) for the FAX gel and were approximated by a second order polynomial. The difference in the curve equation coefficients for the four dose curves was approximately 2% and hence indicating that the response of the FAX gel was not energy dependent. From a linear approximation of the calibration curve a G value of 57.8 ± 3.1 was calculated for a dose range of 0-10 Gy.
The reproducibility of the FAX gel was investigated through preparation and irradiation of a number of gel samples from a single batch. The standard deviations of absorbance measurements for both irradiated and unirradiated FAX gel samples were 1.2% and 1.1% respectively. These errors compare favourably with the standard deviation of 0.5-1 % in the conventional dosimeter (ion chamber) readings. The source of uncertainties in the FAX gel measurements is considered to be due to the continual thermal oxidation of ferrous ions in the FAX gel. Storage lifetime of the unirradiated FAX gel was investigated under a number of different storage enviroments. After 500 hours, the absorbance of the FAX gel stored under refrigeration increased by 25% whereas the absorbance of the FAX gel stored at room temperature and exposed to fluorescence light increased by 80%. The increase in the absorbance of the FAX gels led to a decrease in the dynamic range of the FAX gel response.
A scanning system was constructed to perform two-dimensional scans of a collimated x-ray field, and physical and dynamic wedged fields. For all three fields, the relative dose obtained by the laser based system was found to be within 3% of data acquired using the current standard measurement device (ion chamber). An advantage of the laser based system over the ion chamber was shorter irradiation times were required for data acquisition. These findings demonstrate the potential use of FAX gel phantoms for the acquisition of two-dimensional dose distributions.
An alternative scanning method for the FAX gels based on a video camera imaging system was also investigated. This system acquired a twodimensional dose distribution in a few minutes whereas the laser based system required up to 2 hours. To obtain any quantitative information using the video camera imaging system further investigations involving calibration of the system are required.
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Wang, Yang. "Digital film dosimetry in radiotherapy and the development of analytical applications software." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060223.150107/index.html.
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Farajollahi, Ali Reza. "An investigation into the applications of polymer gel dosimetry in radiotherapy." Thesis, Online version, 1998. http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.284699.
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Li, Bo. "An inductive superconducting transition-edge nano-detector for nano-dosimetry applications." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/848851/.
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In this thesis I have demonstrated the feasibility of using Inductive Superconducting Transition-Edge Sensor (ISTED) as an excellent nanodosimeter for nano-dosimetry applications. This thesis can be divided broadly into two parts. In the first part, I begin by addressing how the study of low energetic ionising particles in liquid water using concepts from classical mechanics is a valid approach, despite being inside the quantum-classical boundary regime. Based on the circumstantial validity condition, I showed that the percentage uncertainties in nanodosimetric quantities due to Heisenberg's uncertainty principle for sub- 1 keV electrons in liquid water as calculated by GEANT4-DNA is not significant enough to cause changes to their distributions. Important nanodosimetric quantities studied in details are ionisation cluster-size distribution, second order of moment for cluster-size distribution (M₂) and the cumulative frequency of ionisation cluster-size distribution from cluster-size two (F₂). In the second part of my thesis, I have focussed on the design, optimisation, fabrication, characterisation of the superconducting devices. An ISTED is made from three components: a) a Superconducting Quantum Interference Device (SQUID), b) a superconducting thin-film and c) a top layer of thin-film Carbon absorber. I have measured the magnetic flux noise of a nanoSQUID of loop dimension 350 nm and nano- Josephson junctions of dimensions 65 nm x 65 nm as 3 x 10⁻¹⁴ Φ₀² in the white noise region. It is shown that the measured nanoSQUID is more than capable of sub- 10 eV energy detection.
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Abbasinejad, Enger Shirin. "Dosimetry Studies of Different Radiotherapy Applications using Monte Carlo Radiation Transport Calculations." Doctoral thesis, Uppsala University, Department of Oncology, Radiology and Clinical Immunology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9277.
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Developing radiation delivery systems for optimisation of absorbed dose to the target without normal tissue toxicity requires advanced calculations for transport of radiation. In this thesis absorbed dose and fluence in different radiotherapy applications were calculated by using Monte Carlo (MC) simulations.
In paper I-III external neutron activation of gadolinium (Gd) for intravascular brachytherapy (GdNCB) and tumour therapy (GdNCT) was investigated. MC codes MCNP and GEANT4 were compared. MCNP was chosen for neutron capture reaction calculations. Gd neutron capture reaction includes both very short range (Auger electrons) and long range (IC electrons and gamma) products. In GdNCB the high-energetic gamma gives an almost flat absorbed dose delivery pattern, up to 4 mm around the stent. Dose distribution at the edges and inside the stent may prevent stent edge and in-stent restenosis. For GdNCT the absorbed dose from prompt gamma will dominate over the dose from IC and Auger electrons in an in vivo situation. The absorbed dose from IC electrons will enhance the total absorbed dose in the tumours and contribute to the cell killing.
In paper IV a model for calculation of inter-cluster cross-fire radiation dose from β-emitting radionuclides in a breast cancer model was developed. GEANT4 was used for obtaining absorbed dose. The dose internally in cells binding the isotope (self-dose) increased with decreasing β-energy except for the radionuclides with substantial amounts of conversion electrons and Auger electrons. An effective therapy approach may be a combination of radionuclides where the high self-dose from nuclides with low β-energy should be combined with the inter-cell cluster cross-fire dose from high energy β-particles.
In paper V MC simulations using correlated sampling together with importance sampling were used to calculate spectra perturbations in detector volumes caused by the detector silicon chip and its encapsulation. Penelope and EGSnrc were used and yielded similar results. The low energy part of the electron spectrum increased but to a less extent if the silicon detector was encapsulated in low z-materials.
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Chen, Yongye. "Study of luminescence signals from quartz and their applications in geothermometry." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/b40203955.
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Nasreddine, Abbas. "Alanine/EPR dosimetry for low to medium energy X-ray radiation processing control." Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAE025.
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L’irradiation par des rayons X de faible à moyenne énergie devient de plus en plus une technique répandue qui remplace des irradiations réalisées par des sources radioactives pour différentes applications telles que l’irradiation du sang, les traitements Sterile Insect Technology et la décontamination des produits alimentaires. Afin de s’assurer que la bonne dose est délivrée au produit, un dosimètre est placé sur ce dernier. Un type de dosimètres utilisé pour ces applications est le dosimètre à l’alanine, qui est équivalent à l’eau dans le cas des photons d’énergie supérieure à 200 keV. Cette thèse présente l’utilisation de l’alanine pour le control et la validation des process d’irradiations réalisés avec des rayons X de faible à moyenne énergie, ainsi que différentes méthodes développées pour déterminer des facteurs correctifs à appliquer à la réponse de ce dosimètre. Ces méthodes reposent sur des mesures expérimentales, des simulations Monte Carlo et des calculs analytiquesNowadays, low to medium energy X-ray irradiators are starting to replace irradiators using radioactivesources, mainly in the fields of blood irradiations, Sterile Insect Technique and food irradiations. A dosimeter is placed on the irradiated product to ensure that the desired dose is well delivered. One of the dosimetry systems that is used in radiation processing is the alanine/EPR dosimetry system. Alanine is considered as water equivalent, from a dosimetric point of view for photon energies that are higher than 200 keV. However, it loses its water equivalency for lower photon energies.This thesis presents the use of alanine for the control and validation of irradiation processes performed with low to medium energy X-rays, as well as different methods developed to determine corrective factors to be applied to the response of this dosimeter. These methods are based on experimental measurements, Monte Carlo simulations and analytical calculations
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Zvereva, Alexandra [Verfasser], and Katia [Akademischer Betreuer] Parodi. "Advanced modeling for personalized dosimetry in nuclear medicine applications / Alexandra Zvereva ; Betreuer: Katia Parodi." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1170061192/34.
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McCowan, Peter Michael. "in vivo patient dose verification of volumetric modulated arc therapy including stereotactic body radiation treatment applications using portal dose images." Medical Physics, 2015. http://hdl.handle.net/1993/31120.
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The complexity of radiation therapy delivery has increased over the years due to advancements in computing and technical innovation. A system of dose delivery verification has the potential to catch treatment errors and therefore improve patient safety. The goal of this thesis was to create a portal image-based in vivo dose reconstruction model for volumetric modulated arc therapy (VMAT) deliveries, specifically for stereotactic body radiation therapy (SBRT). This model-based approach should be robust and feasible within a clinical setting. VMAT involves the modulation of dose rate, gantry speed, and aperture shaping while the treatment gantry (i.e., x-ray beam) rotates about the patient. In this work, portal images were acquired using an amorphous silicon electronic portal imaging device (a-Si EPID).
A geometrical characterization of the linear accelerator (linac) during VMAT delivery was performed. An angle adjustment method was determined which improves each EPID’s angular accuracy to within ±1° of the true physical angle.
SBRT delivers large doses over fewer fractions than conventional radiotherapy, therefore, any error during an SBRT delivery will have a greater impact on the patient. In this work, a robust, model-based SBRT-VMAT dose reconstruction verification system using EPID images was developed. The model was determined to be clinically feasible.
The accuracy of a 3D in vivo dose reconstruction, using all the EPID images acquired during treatment, is sensitive to the chosen frame averaging per EPID image: the greater the frame averaging, the larger the reconstruction error. Optimization of the EPID frame averaging number as a function of average linac gantry speed and dose per fraction were determined.
The EPID-based in vivo dose reconstruction model for SBRT-VMAT developed here was determined to be robust, accurate, and clinically feasible as long as adjustments were made in order to correct for EPID image geometrical errors and frame-averaging errors.May 2016
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Chen, Yongye, and 陳永曄. "Study of luminescence signals from quartz and their applications in geothermometry." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40203955.
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Zlateva, Yana. "Investigation of Cherenkov emission with applications in dosimetry, image guidance and intensity modulation in radiation therapy." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121558.
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The aims of this work are to validate the potential application of Cherenkov emission (CE) in radiotherapy dosimetry, online imaging and beam modulation by analysis of its correlation with radiation dose and by a spectral shift to the near-infrared (NIR) window of biological tissue in order to maximize its detection. This work makes an original contribution to scientific knowledge by effectively correlating radiation dose and CE in two dimensions, using an optical fiber and grating spectrometer, without need for a computer-generated spatially variant conversion factor or a fluorescent dye, and by successfully shifting CE to the NIR in a tissue-simulating phantom with the use of quantum dots (QDs).Radiation dose was correlated with CE via both computer simulation and experimental measurements using clinical 6-18 MeV electron beams. A Monte Carlo (MC) CE simulator was designed using the Geant4 simulation toolkit. In order to maximize the signal, beam incidence angle was optimized through simulation and experiment and the feasibility of two-fiber detection was assessed. Phantoms used in the experiments were a water tank and a tissue-simulating phantom composed of water, Intralipid® and beef blood. The optical detection system consisted of a multi-mode step-index fiber optic cable (numerical aperture = 0.22 for dose versus Cherenkov studies), positioned out of the beam and connected to a single-channel diffraction grating spectrometer incorporating a front- or back-illuminated charge-coupled device (CCD). A cylindrical ionization chamber was used for dose measurements. CdSe/ZnS core-shell QDs, emitting at (650 ± 10) nm, were used to achieve a NIR shift of the CE signal.A preliminary software analysis indicated a strong correlation between radiation dose and CE with a Pearson correlation coefficient larger than 0.99. A beam incidence angle of 50° relative to the surface normal produced a CE maximum along the horizontal fiber. An angle of 47° (corresponding to more than 80% of the maximum signal) was adopted in order to maximize the scan depth by avoiding beam perturbation due to setup components and fiber protrusion into the field. Dose versus CE correlation was investigated via water phantom ion chamber scans along the beam central axis and optical fiber scans with the fiber tip positioned at the field edge. With all data sets normalized to 1, the effective point of measurement of the optical system for 18, 12 and 6 MeV clinical electron beams was found to be at depths of approximately 1.7, 0.8, and 0.1 cm, respectively, downstream from the fiber axis, with a Pearson correlation coefficient for all (simulated and experimental) data larger than 0.99. CE by an 18 MeV electron beam was successfully shifted towards 650 nm in water and in a tissue-simulating phantom. Smaller field sizes and larger QD depths resulted in a lower signal, though a shift was still apparent for a 1 cm depth of the QDs. Statistical data analysis indicated no noise bias and that radiation might have impacted the spectrometer electronics.The results of this work validate the potential for application of CE in radiotherapy dosimetry, online imaging and intensity modulation based on tumor microenvironment information, such as oxygenation, since CE is intrinsic to the beam, non-ionizing and can be detected outside the beam, and the QDs used for the experiments are photostable, tunable, and can be modified to incorporate molecular reporters. Future work involves the use of a multi-channel spectrometer for simultaneous collection of main, reference and background signals, incorporation of a lens or a single-mode fiber to reduce the sensitive volume, as well as development of better spectral data extraction techniques. It is expected that the proposed technique will be applicable to 3D dose mapping by means of diffuse optical tomography, online CE imaging and localization during radiotherapy, and beam modulation based on tumor microenvironment information.Les objectifs de cette étude sont de valider la potentielle application de l'émission Cherenkov (EC) pour la dosimétrie en radiothérapie, pour l'imagerie en temps réel et pour la modulation des faisceaux par l'analyse de sa corrélation avec la dose de rayonnement et par un décalage spectral vers la fenêtre infrarouge proche (FIP) des tissus biologiques afin de maximiser sa détection. Ce travail apporte une contribution originale aux travaux antérieurs en corrélant efficacement, d'une part, la dose de rayonnement et l'EC en 2 dimensions à l'aide d'une fibre optique et d'un spectromètre à réseau, et ce, sans l'aide d'un facteur de conversion variant spatialement et généré par ordinateur ou d'un colorant fluorescent, et d'autre part, en effectuant avec succès le déplacement de l'EC à la FIP dans un fantôme simulant les tissus biologiques grâce à l'utilisation de points quantiques (PQs).La dose de rayonnement a été corrélée avec l'EC à la fois par simulation informatique et par mesures expérimentales. Un simulateur Monte Carlo (MC) de l'EC a été conçu en utilisant la plateforme de simulation Geant4. Les fantômes utilisés dans les expériences consistaient d'un réservoir d'eau et d'un fantôme simulant les tissus biologiques composés d'eau, d'Intralipid® et de sang de boeuf. Le système de détection optique est composé d'un câble de fibre optique multi-mode à saut d'indice, placé hors du faisceau d'électron et relié à un spectromètre à réseau de diffraction à canal unique comprenant un dispositif à couplage de charge éclairé par l'avant ou l'arrière. Des points quantiques CdSe/ZnS, émettant à (650 ± 10) nm, ont été utilisés afin de réaliser un décalage de l'EC vers la FIP.Une analyse préliminaire a indiqué une forte corrélation entre la dose de rayonnement et de l'EC avec un coefficient de corrélation de Pearson supérieur à 0.99. La corrélation de la dose en fonction de l'EC a été étudiée via des scans de la chambre d'ionisation dans le fantôme d'eau le long de l'axe central du faisceau ainsi que par des scans de fibre optique avec la pointe de la fibre positionnée sur le bord du champ du faisceau. Après normalisation, le point effectif de mesure du système optique des faisceaux d'électrons cliniques de 18, 12 et 6 MeV, s'est révélé être situé à des profondeurs respectives de 1.7 cm, 0.8 cm et 0.1 cm, et ce, en aval de l'axe de la fibre, avec un coefficient de corrélation Pearson pour toutes les données de plus de 0.99. La fenêtre d'EC d'un faisceau d'électrons de 18 MeV a été décalée avec succès vers 650 nm dans le réservoir d'eau, confirmant sa capacité à stimuler la photoluminescence de CdSe/ZnS, et dans le fantôme simulant les tissus biologiques. La diminution de la taille des champs ainsi que l'augmentation de la profondeur des PQs ont eu pour effet de diminuer le signal, quoiqu'un décalage du signal était encore apparent à 1 cm de profondeur. L'analyse statistique des données nous a confirmé que le bruit n'a pas d'impact significatif sur le signal, mais que le rayonnement peut avoir un impact sur les composantes électroniques du spectromètre.Les résultats de ce travail confirment le potentiel d'application de l'EC pour la dosimétrie en radiothérapie, pour l'imagerie en temps réel et pour la modulation d'intensité des faisceaux en fonction des informations relatives au microenvironnement des tumeurs, comme l'oxygénation. En effet, l'EC est intrinsèque au faisceau d'électrons, est non-ionisante et peut être détectée en dehors du faisceau. De plus, les PQs utilisés dans nos expériences sont photostables et peuvent être modifiés afin d'intégrer des molécules pouvant nous informer sur la microbiologie des tumeurs. Il est prévu que la technique proposée sera applicable à la cartographie de dose en 3D au moyen de la tomographie optique diffuse, à l'imagerie par EC en temps réel et la localisation spatiale durant la radiothérapie, ainsi qu'à la modulation du faisceau en fonction du microenvironnement de la tumeur.
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Jhala, Ekta. "Investigation of Dosimetric Characteristics and Exploration of Potential Applications of Amorphous Silicon Detector." Thesis, University of Canterbury. Physics and Astronomy, 2006. http://hdl.handle.net/10092/1350.
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The ability of the electronic portal imaging device (EPID) to acquire a large two-dimensional array of digitized x-ray data in real time is extremely attractive for dosimetric measurements. To evaluate the potential use of an EPID for portal dose measurement in Wellington Blood and Cancer Centre, some dosimetric characteristics of the Varian's PortalVisionTM aS500 were investigated. PortalVisionTM incorporates an amorphous silicon detector (aSi). Some potential applications of EPID in linac QA were also explored. The EPID's performance for linearity with MU and dose rate was verified and it was found to be proportional over the entire measured range. Short term repeatability was found to be excellent. An investigation of calibration method to improve dosimetric accuracy demonstrated two methods of avoiding detector saturation. Firstly, acquiring flood field with the use of additional buildup and secondly, increasing the source to detector distance for calibration. A study of EPIDs behaviour under conditions of varying dose rate which commonly arise in EDW treatment techniques was carried out. The EPID exhibited a field size dependence in addition to a 8% discrepancy on the `hot edge' of EDW profiles. Further investigation into the field size dependence and the discrepancy at hot edge is required. EPIDs ability to acquire asymmetric field profile was also investigated. The profiles acquired using EPID deviated in shape and magnitude by upto 16% from the ion chamber profiles. Some potential applications of EPID to perform QA of linac beam properties, its ability to perform optical and mechanical linac QA have been explored. The EPID's capability to give constant output, flatness, symmetry, wedge angle and wedge factors with high level of accuracy and reproducibility was demonstrated. EPID was also found to be objective, efficient and feasible for performing optical linac QA. The use of EPID for linac QA could be simplified by improving the available software analysis tools thus making it more efficient.
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Manninen, A. L. (Anna-Leena). "Clinical applications of radiophotoluminescence (RPL) dosimetry in evaluation of patient radiation exposure in radiology:determination of absorbed and effective dose." Doctoral thesis, Oulun yliopisto, 2014. http://urn.fi/urn:isbn:9789526206240.
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Abstract Computed tomography (CT) and interventional procedures cause relatively high patient doses compared with other imaging modalities in radiology. The optimization of the imaging equipment and procedures is important and necessary due to the known risks caused by ionization radiation. The different irradiation geometries and dose units between imaging techniques complicate the comparison of patients’ radiation exposure. Absorbed doses (D) of organs predict the tissue reactions of the procedures, while effective dose (E) is a useful means of comparing the stochastic effects of the different imaging procedures. A and E can be estimated from dosimetric measurements in a phantom. In vivo measurements are used during a radiological examination. In the present thesis, various properties of radiophotoluminescence dosimeters (RPLD) were investigated to verify the applicability of RPL dosimetry in radiology. The absorbed dose was determined in vaginal fornix of seven pregnant women, in the area near the head of the fetus during prophylactic catheterization before uterine artery embolization (UAE). The evaluation of the radiation exposure of digital subtraction angiography (DSA) and computed tomography angiography (CTA) was performed using an anthropomorphic phantom. Absorbed doses of organs and effective dose were determined for a typical four-vessel angiography of the cerebral area, including intracranial vessels, and for the cervicocerebral area, including both cervical and intracranial vessels. RPLD shows excellent dose linearity and minimal fading. The low dose detection threshold was determined to be 20 µGy with a coefficient of variation (CV) of 12.2%. The methodology is independent of photon energy in the energy range used in radiology. For seven patients studied, the mean value of D in vaginal fornix was 11.2 mGy (range 2.2–28.7) being low dose study when pulsed fluoroscopy with an optimized protocol is used without angiography exposures. In the assessment of cerebral vessels, the effective dose for CTA was approximately one-fifth of the dose compared with DSA. The dose for cervicocerebral vessels CTA was approximately one third higher compared with DSA. Conversion factors from the DAP and the DLP to the effective dose were calculated for the specific angiographic protocols. RPL dosimetry shows sufficient reliability in measuring radiation doses in radiologyTiivistelmä Tietokonetomografiakuvauksissa ja toimenpideradiologisissa tutkimuksissa potilaan säteilyaltistus on suhteellisesti korkeampi verrattuna muihin radiologisiin kuvausmenetelmiin. Kuvauslaitteiden erilaiset kuvausgeometriat ja annosyksiköt hankaloittavat potilaan säteilyaltistuksen vertailua eri tutkimusmenetelmien välillä. Kudokseen absorboituneen annoksen (D) avulla arvioidaan ionisoivan säteilyn suoraa haittavaikutusta kudokselle, kun taas efektiivisen annoksen (E) määrittämisellä arvioidaan säteilyn satunnaista haittaa. D ja E voidaan mitata annosmittarilla käyttäen potilasvastinetta. In vivo mittauksella saadaan annostietoa tutkimuksen aikana suoraan potilaasta. Radiofotoluminesenssiannosmittarin (RPLD) soveltuvuus radiologisiin annosmittauksiin varmistettiin tutkimalla mittarin eri fysikaalisia ominaisuuksia. RPLD:a käytettiin intravaginaalisen annoksen mittauksessa seitsemällä raskaana olevalla naisella. Potilaille tehtiin massiivisen verenvuodon ehkäisemiseksi kohdun valtimosuonten katetrointi läpivalaisuohjattuna ennen kohtuvaltimoiden tukkimishoitoa (UAE). Mittaustulokset antavat tietoa kudokseen absorboituneesta annoksesta lähellä syntymätöntä lasta. Tietokonetomografia-angiografia (TTA) ja digitaalinen subtraktioangiografia (DSA) tutkimusten annosmittaukset tehtiin potilasvastineessa käyttäen RPLD:a. Elinannoksista laskettiin efektiivinen annos aivovaltimoiden ja aivokaulavaltimoiden angiografiatutkimuksille. RPL -annosmittausmenetelmän havaittiin olevan lineaarinen ja annoksen häviäminen mittarista on vähäistä. Matalan annoksen mittausraja oli 20 µGy 12.2% toistettavuudella. RPLD on riippumaton säteilyenergiasta radiologiassa käytettävällä energia-alueella. Seitsemän potilaan keskimääräinen absorboitunut annos oli 11.2 mGy (vaihteluväli 2.2–28.7 mGy) emättimen pohjukasta mitattuna. Annostaso osoittaa, että katetrointitoimenpide on matala-annostutkimus, kun toimenpide tehdään läpivalaisuohjauksessa, eikä angiografisia kuvia käytetä. Aivovaltimoiden TTA:n efektiivinen annos oli viidesosa DSA menetelmän annoksesta. Aivokaulavaltimoiden TTA:n efektiivinen annos oli arviolta 35% korkeampi kuin DSA menetelmän annos. Konversiokertoimet DAP ja DLP yksiköistä efektiivisen annoksen laskemiseksi määritettiin tutkimuksessa käytetyille kuvausohjelmille. RPL -menetelmä osoitti riittävää luotettavuutta radiologisten säteilyannosten mittauksessa
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Lemaréchal, Yannick. "Dosimétrie pour des applications de radiothérapie en utilisant les processeurs graphiques." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0035.
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Le cancer de la prostate est le cancer le plus fréquemment diagnostiqué en France chaque année. Il est responsable d’environ 10 % des morts liées au cancer. Les principaux traitements sont la chirurgie et la radiothérapie. Cette dernière concerne environ 60 % à 70 % des patients pris en charge en oncologie. La radiothérapie consiste à délivrer la dose la plus élevée possible à une cible tumorale, via des rayonnements ionisants, tout en limitant au maximum la dose délivrée aux tissus sains et organes à risque (OAR) environnants. Cette pratique requiert un contrôle sans faille de la dose délivrée au patient car une déviation de la prescription médicale peut réduire l’efficacité du traitement des volumes tumoraux. Elle peut également avoir des conséquences graves sur le patient dues à l’irradiation excessive des tissus sains. Un moyen pour évaluer de façon précise la dose délivrée est de simuler l’interaction rayonnement matière à l’intérieur du patient par simulation Monte-Carlo (SMC). Ceci exige une capacité de calcul importante notamment pour simuler les milliards de particules nécessaires à l’évaluation de la dosimétrie. Le temps nécessaire pour obtenir un résultat satisfaisant peut varier de quelques heures à plusieurs jours. Dans ce contexte, le moteur de simulation Monte-Carlo GGEMS (GPU GEant4-based Monte-Carlo Simulation), basé sur l’utilisation de cartes graphiques (GPUs), a pu être développé. Les effets physiques modélisés se basent sur le code Monte-Carlo générique Geant4 réputé et validé. Ce logiciel tient compte de différents types de simulations comme la radiothérapie externe ou les techniques de curiethérapie bas débit et haut débit de dose. Ces exemples ont nécessité la modélisation précise et l’utilisation de plusieurs types de géométries comme des volumes voxélisés, analytiques ou maillés. Concernant la radiothérapie, il n'existait pas de code Monte-Carlo utilisant les architectures GPUs prenant en considération l'ensemble de l'appareil de traitement. Dans ce contexte, nous avons développé un modèle de source paramétrée reproduisant scrupuleusement le faisceau d'émission et permettant une utilisation sur GPU. Nous avons modélisé analytiquement les géométries des mâchoires. Le collimateur multi-lames est quant à lui formé par un ensemble de triangles (maillage). La navigation des électrons dans un volume voxélisé a également été développée. Nous avons utilisé comme exemple l'accélérateur Novalis TrueBeam® Stx. Nous pouvons ainsi effectuer des simulations Monte-Carlo reproduisant fidèlement cet accélérateur linéaire. L’ensemble de l’appareil a été validé à l’aide de comparaisons avec des mesures expérimentales ou avec des simulations Monte-Carlo de référence. Finalement, nous avons développé une plateforme de simulation Monte-Carlo utilisant les architectures GPUs pour des applications de curiethérapie et de radiothérapie externe. Cette plateforme comprend la navigation des photons et des électrons. Elle gère également les volumes voxélisés, analytiques (cylindre, pavé) et maillés. Les sources d'émission des particules sont modélisées pour reproduire fidèlement leur modèle de référence. Les facteurs d'accélération par rapport à Geant4 sont compris entre 40 et 568 selon l'application. Des applications de GGEMS dans des conditions cliniques, notamment en curiethérapie, sont la prochaine étape du développementProstate cancer is the most frequently diagnosed cancer in France each year. It is responsible for about 10% of deaths related to cancer. The main treatments are surgery and radiation therapy. The latter concerns about 60 % to 70 % of patients treated in oncology. The aim of radiation therapy is to deliver the highest possible dose to the tumor target, via ionizing radiation, while minimizing the dose delivered to surrounding healthy tissues and organs at risk (OAR). This practice requires a flawless dose control for patient safety as far as a deviation from the medical prescription could reduce treatment efficiency This could also lead to an excessive irradiation of healthy tissues and cause serious damage to the patient. A way to evaluate the dose delivered to the patient is to track particles in the matter using Monte Carlo simulations (MCS). This requires a large computation time specially to simulate billion of particles and to evaluate the associated dosimetry. The time required to obtain a satisfactory result may vary from hours to days. In this context, the Monte Carlo simulation engine GGEMS (GPU Geant4-based Monte Carlo Simulation), based on the use of graphics cards (GPUs), has been developed. Physics effects are based on the generic and validated Monte Carlo code Geant4. This software is able to handle various types of simulations such as external beam radiation therapy and low dose rate or high dose rate brachytherapy. These examples need an accurate modelling and the use of several types of geometries such as for voxelised, analytical or meshed volumes. We analytically modeled jaw geometries. The multi-leaf collimator was formed by a set of triangles (mesh). Electron navigation in a voxelised volume was also developed. We used the example of the Novalis TrueBeam® Stx accelerator. We can then perform Monte Carlo simulations reproducing the linear accelerator. The entire device was validated using comparisons with experimental measurements or with Monte Carlo simulations from Geant4 Finally, we have developed a Monte Carlo simulation platform using GPU architectures for applications of brachytherapy and external beam radiotherapy. This platform includes photons and electrons navigation. It also manages voxelised, analytical (cylinder, cube) and mesh volumes. The particle emission sources are modelled to accurately reproduce their reference model. The acceleration factors from Geant4 are between 40 and 568 depending on the application. GGEMS Applications under clinical conditions, including brachytherapy, are the next development step
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Fung, Karl Ka Lok. "Investigation of dosimetric characteristics of the high sensitivity LiF : Mg,Cu,P thermoluminescent dosemeter and its applications in diagnostic radiology." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/752/.
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FASASI, MUSIBAU. "Modelisations des reponses du silicium et du tellure de cadmium aux rayonnements gamma et neutron : applications a la dosimetrie." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13128.
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Modelisation des reponses des detecteurs a semiconducteurs lorsque ceux-ci sont utilises en mode de comptage en vue de leur application a la dosimetrie gamma et neutron (thermique et rapide). A l'aide de trois programmesm de monte carlo, les valeurs optimales des parametres necessaires pour la mise au point des dosimetres individuels sont obtenues
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Howland, Matthew. "Transcriptomic and Secretomic Profiling of Isolated Leukocytes Exposed to Alpha-Particle and Photon Radiation - Applications in Biodosimetry." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26081.
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The general public is at risk of ionising-radiation exposure. The development of high-throughput methods to triage exposures is warranted. Current biodosimetry techniques are low-throughput and encumbered by time and technical expertise. Although there has been an emergence of gene-profiling tools for the purpose of photon biodosimetry, similar capacities do not exist for alpha-particle radiation. Herein is the first genomic study useful for alpha-particle radiation biodosimetric triage. This work has identified robust alpha-particle induced gene-based biomarkers in isolated, ex-vivo irradiated leukocytes from multiple donors. It was found that alpha-particle and photon radiation elicited similar transcriptional responses, which could potentially be distinguished by aggregate-signature analysis. Although no distinct genes were sole indicators of exposure type, clustering algorithms and principal component analysis were able to demarcate radiation type with some success. By comparing the biological effects elicited by photon and alpha-particle radiation, significant contributions have been made to the field of radiation biodosimetry.
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Treccani, Matteo. "Qualification of an X-ray unit for dosimetrical application." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669449.
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Este proyecto de doctorado se centra en la evaluación de calidad de una unidad de rayos X para aplicaciones dosimétricas.
Esta tesis describe todo el proyecto en tres secciones diferentes.
La primera parte puede considerarse una introducción para presentar los conceptos e instrumentos utilizados para este trabajo. La base teórica del principio de funcionamiento de un tubo de rayos X se explica en el Capítulo 1. El Capítulo 2 muestra las magnitudes y el sistema de unidades de Protección Radiológica. Estos dos primeros capítulos representan los antecedentes teóricos de mi tesis. El Capítulo 3 muestra el laboratorio montado durante la primera parte de mi trabajo de doctorado. La unidad de irradiación y el laboratorio relacionado se pusieron a punto en el marco de una colaboración entre los Laboratorios Nacionales de Frascati del INFN (INFN - LNF), la Agencia Espacial Italiana (ASI) y el Consorzio di ricerca Hypatia. El aparato de rayos X funciona entre 40 y 120 kV con corrientes de hasta 5 mA. Se pueden implementar diferentes filtraciones de acuerdo con la calidad de haz deseada. Un banco mecánico permite colocar dispositivos y muestras a diferentes distancias del ánodo del tubo de rayos X.
La segunda parte muestra los principales resultados obtenidos con diferentes experimentos y pruebas para calificar la salida de radiación del tubo de rayos X:
• diseño y desarrollo de una cámara de ionización para medir la salida dependiente del tiempo de la unidad de rayos X (Capítulo 4);
• determinación de la posición del foco del tubo de rayos X, que es un punto de referencia importante de la línea de irradiación (Capítulo 5);
• verificación experimental de la calidad del haz a través de mediciones HVL (Espesor de semireducción - Half Value Layer) con la cámara de ionización para la elección de combinaciones adecuadas de kilovoltios-filtración para lograr calidades de radiación bien identificadas, según lo especificado por las Normas Internacionales relevantes (ISO 4037). Los haces de la serie de espectro estrecho (serie ISO 4037 N) se seleccionaron porque su distribución de energía aproximadamente monoenergética es muy adecuada para estudiar la respuesta de los dispositivos en función de la energía del fotón. La concordancia entre los valores ISO y los experimentales es excelente: la discrepancia es inferior a aproximadamente el 5% (Tabla 6-3, Capítulo 6).
• estudio sobre la uniformidad del campo de rayos X (Capítulo 7), que es una tarea importante que debe cumplir el haz de rayos X, ya que es importante que todas las áreas de campo sean equivalentes y que la dosis impartida al dispositivo bajo prueba sea independiente de la posición en que se coloque. Se utilizaron dos técnicas de medición diferentes para verificar la uniformidad. La primera se basa en un detector pasivo, película Gafchromica, y la segunda emplea un detector de silicio que funciona en modo corriente. La variabilidad total del campo es aproximadamente del 11% dentro de una región central de 8 cm de radio (párrafo 7.4, Capítulo 7).
• medición espectral de los haces de rayos X utilizando espectrómetros de fotones basados en semiconductores (detectores de silicio y de telurato de cadmio). Estas mediciones son básicas para verificar la forma del espectro continuo de radiación de frenado y las energías de punto final de las componentes espectrales, además de las mediciones de calidad de HVL (Capítulo 8). Los espectros confirman lo que se esperaba de las mediciones de HVL: utilizando las combinaciones de kilovoltios-filtración adecuadas (escritas en la Tabla 6-3) es posible lograr las calidades de radiación bien identificadas de la serie N, la serie estrecha de ISO 4037, útil como referencia de calibración
La actividad de la última parte de mi tesis doctoral se centró en un innovador detector activo para dosimetría de cristalino (Capítulo 9). Durante los últimos años se ha puesto de manifiesto la necesidad de una reevaluación detallada de la radiosensibilidad del cristalino. Varios estudios epidemiológicos han destacado una mayor incidencia de cataratas que la prevista previamente. Por estas razones, la ICRP redujo el límite de exposición para los trabajadores de 150 mSv por año a 20 mSv en un año promedio durante períodos definidos de cinco años consecutivos, sin que en ningún año se excedan los 50 mSv (ICRP 2011). Por lo tanto, el gran interés en este tema es la evaluación esencial de la dosis ocupacional en cristalino y la protección del ojo. Gracias a la calificación física del tubo de rayos X bajo un punto de vista metrológico, fue posible utilizar esta instalación de irradiación como banco de pruebas para el desarrollo y pruebas de tipo (estudio sobre energía y respuesta angular) de un prototipo de un dosímetro de cristalino basado en semiconductores y desarrollado dentro del equipo de trabajo. Esta parte innovadora de mi trabajo de doctorado representa un estudio de I + D sobre la necesidad de dosimetría operativa.This PhD project is focused on the qualification of an X-ray unit for dosimetrical applications. This thesis describes all the project in three different sections. The first part can be considered an introduction for depicting concepts and instruments used for this work. The theorical basis of the working principle of an X-ray tube is explained in Chapter 1. Chapter 2 shows the quantities and units system on Radiation Protection. These first two chapters represent the theoretical background of my thesis. Chapter 3 depicts the laboratory assembled during the first part of my PhD work. The irradiation unit and the related laboratory were set up in the framework of a collaboration between INFN - Frascati National Laboratories (INFN - LNF), the Italian Space Agency (ASI) and Consorzio di ricerca Hypatia. The X-ray apparatus operates from 40 to 120 kV with currents up to 5 mA. Different filtrations can be implemented according to the desired beam quality. A mechanical bench allows positioning devices and samples at different distances from the anode of the X-ray tube. The second part shows the main results obtained with different experiments and tests to qualify the radiation output of the X-ray tube: • design and development of a monitor ion-chamber to measure the time-dependant output of the X-ray unit (Chapter 4); • determination the X-ray tube focus position, which is an important reference point of the irradiation line (Chapter 5); • experimental verification of the beam quality through HVL (Half Value Layer) measurements with ion-chamber for the best choice of adequate kilovolt-filtration combinations in order to achieve well-identified radiation qualities, as specified by relevant International Standards (ISO 4037). The beams from the narrow spectrum series (ISO 4037 N-series) were selected because their roughly mono-energetic energy distribution is well suited to study the response of devices as a function of the photon energy. The accordance between ISO values and experimental ones is excellent: the discrepancy is less than about 5% (Table 6-3, Chapter 6) . • study on the X-ray field uniformity (Chapter 7), which is an important task that the X-ray beam must comply with, because it is important that all the field areas are equivalent and wherever the device under test is placed, it is exposed to the same dose. Two different measurements techniques were involved to verify the uniformity. The first is based on a passive detector, Gafchromic film, and the second employs a silicon detector operating in current mode. The total field variability is about 11% within a central region of 8 cm radius (paragraph 7.4, Chapter 7). • spectral measurement of the X-ray beams using semiconductor-based photon spectrometers (Silicon and Cadmium-Telluride detector). These measurements lead a role for checking the continuum shape of bremsstrahlung spectrum and the endpoint energies of the spectral components in addition to the quality measurements of HVLs (Chapter 8). The spectra confirm what expected from HVL measurements: using the proper kilovolt-filtration combinations (written in the Table 6-3) is possible to achieve the well-identified radiation qualities of the N-series, the narrow series of ISO 4037, useful as calibrating reference. The activity for the last part of my PhD thesis was focused on an innovative active detector for eye-lens dosimetry (Chapter 9). During the last years the need of a detailed re-evaluation of the eye lens radio-sensitivity was put in evidence. Various epidemiological studies highlighted a higher incidence of cataracts than previously foreseen. For these reasons the ICRP reduced the exposure limit for workers from 150 mSv per year to 20 mSv in a year averaged over defined periods of five consecutive years, with no single year exceeding 50 mSv (ICRP 2011). Therefore, the keen interest on this topic is for the essential evaluation of the occupational eye dose and eye protection. Thanks to the physical qualification of the X-ray tube under a metrological point of view, it was possible to use this irradiation facility as test bench for the development and type testing (study on energy and angular response) of a semiconductor-based prototype of an eye-lens dosimeter developed within the work team. This innovative part of my PhD work represents a R&D study on a need for operational dosimetry.
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Vismara, Marcus Vinícius Gonçalves [UNESP]. "Estudo das propriedades dosimétricas de polímeros conjugados." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/99657.
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Este trabalho teve como objetivo a investigação da interação de radiação gama com três polímeros: o polímero Poli(2-metóxi, 5-(2'-etil-hexilóx)-1,4- fenileno vinileno) (MEH-PPV)n e os polímeros solúveis em água Poly {[2,5-bis(2-(N,N-diethylamino)ethoxy) -1,4 -phenylene]-alt-1,4-phenylene} e o Poly [(2,5-bis (2 - (N,N - diethylammonium bromide) ethoxy) - 1,4 -phenylene) - alt - 1,4-phenylene]. O polímero MEH-PPV foi dissolvido nos solventes orgânicos clorofórmio e bromofórmio, já os outros dois polímeros, em água destilada e solução de HCI 1M. As amostras foram preparadas em várias concentrações e irradiadas com doses que variaram desde 0,01 Gy, sendo que cada amostra foi irradiada com apenas uma dose. Os resultados foram avaliados com técnicas espectroscópicas, sendo elas, espectroscopia de absorção óptica UV-visível e espectroscopia de fluorescência. Foi avaliada a alteração na posição do pico principal de absorção óptica com a dose absorvida pelas amostras. Como resultado principal, observou-se que os polímeros solúveis em água não apresentam alteração espectral após serem irradiados. Não sendo interessante para aplicação dosimétrica. Já para as amostras do polímero MEH-PPV diluídas em bromofórmio apresentaram alta sensibilidade para doses inferiores a 1 Gy, e apresentaram certa linearidade com a dose recebida (fator importante para aplicação dosimétrica). Para as amostras em clorofórmio, não foi observado deslocamento significativo do escpectro de absorção para doses inferiores a 1 Gy. No entanto para doses de 1 Gy à 90 Gy, o comportamento observado pode ser descrito por duas regiões lineares: uma com maior inclinação da reta para doses até cerca 30 Gy, e outro com inclinação da reta menor para doses entre 30 Gy e 90 Gy. O comportamento linear, assim como a inclinação da reta, do deslocamento da posição...
The subject of this work is the investigation of gamma radition interaction with tree polymers: the polymer Poli(2-metóxi, 5-(2'-etil-hexilóx)-1,4- fenileno vinileno) (MEH-PPV)n e os polímeros solúveis em água Poly {[2,5-bis(2-(N,N-diethylamino)ethoxy) -1,4 -phenylene]-alt-1,4-phenylene} e o Poly [(2,5-bis (2 - (N,N - diethylammonium bromide) ethoxy) - 1,4 -phenylene) - alt - 1,4-phenylene]. The MEH-PPV polymer was dissolved in organic solvents, choloroform and bromoform, the other two polymers in distilled water and 1 M aqueous HCI solution. The samples were prepared at various concentrations and irradiated with doses ranging from 0.01 Gy to 90 Gy. The results were evaluated by spectroscopic techniques, which were, UV-visible absorption spectroscopy and fluorescence spectroscopy. They were evaluated the changes in the position of main optical absorption peak with the dose absorbed by the samples. As main result, it was observed that water-soluble polymers did not show spectral change after being irradiated. For dosimetric application this results are not interesting. For the MEH-PPV polymer samples diluted in bromoform presented highly sensitive to doses below 1 Gy, and showed some linearity with the dose received. For samples in chloroform, doses below 1 Gy did not showed significant shift in the absorption spectra. However, the samples irradiated with doses from 1 Gy to 90 Gy, the behavior can be described by two linear regions: one with a higher slope for doses up to about 30 Gy, and another with a lower slope for doses between 30 Gy and 90 Gy. A greater slope to doses up to about 30 Gy, and another with lower slope to doses between 30 and 90 Gy. The linear behavior and the slope of the main peak position is a important factor for dosimetric application. At the same time, a study of stability of the samples was performed. It was observed that the MEH-PPV samples in bromoform... (Complete abstract click electronic access below)
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Petitfils, Aurélie. "Propriétés thermoluminescentes du diamant CVD : applications à la dosimétrie des rayonnements ionisants." Toulouse 3, 2007. http://thesesups.ups-tlse.fr/44/.
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Ce travail souligne l'intérêt du diamant synthétique pour la dosimétrie par thermoluminescence (TL) et plus particulièrement pour la radiothérapie. La première partie de ce travail porte sur les propriétés thermoluminescentes et dosimétriques du diamant polycristallin élaboré par synthèse CVD. Les résultats obtenus montrent que ce matériau est bien adapté pour la dosimétrie médicale par TL. La deuxième partie de ce travail s'intéresse à l'application du diamant CVD en radiothérapie. Des mesures de profils de dose, de rendements en profondeur sous photons et électrons, la cartographie d'un faisceau d'électrons et des mesures en Radiothérapie Conformationnelle avec Modulation d'Intensité ont été réalisées avec nos échantillons et comparées à la réponse d'un détecteur de référence. L'ensemble des résultats obtenus montre tout le potentiel du diamant CVD pour une utilisation comme dosimètre TL dans les zones à forts gradients de dose et pour le contrôle des faisceaux d'accélérateurs de traitementRemarkable properties of synthetic diamond (human soft tissue equivalence, chemical stability, non-toxicity) make this material suitable for medical application as thermoluminescent dosimeter (TLD). This work highlights the interest of this material as radiotherapy TLD. In the first stage of this work, we looked after thermoluminescent (TL) and dosimetric properties of polycristalline diamond made by Chemically Vapor Deposited (CVD) synthesis. Dosimetric characteristics are satisfactory as TLD for medical application. Luminescence thermal quenching on diamond has been investigated. This phenomenon leads to a decrease of dosimetric TL peak sensitivity when the heating rate increases. The second part of this work analyses the use of synthetic diamond as TLD in radiotherapy. Dose profiles, depth dose distributions and the cartography of an electron beam obtained with our samples are in very good agreement with results from an ionisation chamber. It is clearly shown that CVD) diamond is of interest to check beams of treatment accelerators. The use of these samples in a control of treatment with Intensity Modulated Radiation Therapy underlines good response of synthetic diamond in high dose gradient areas. These results indicate that CVD diamond is a promising material for radiotherapy dosimetry
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Traore, Issiaka. "Etude et caractérisation des fonctions de réponse des détecteurs solides de traces nucléaires : applications à la dosimétrie radon et neutron." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01067060.
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Cette thèse a été préparée en cotutelle entre l'Université de Strasbourg et l'Université des SciencesTechniques et Technologies de Bamako (Mali). Elle s'articule principalement autour de la caractérisation des Détecteurs Solides de Traces Nucléaires (DSTN) afin de les utiliser pour la métrologie du radon et des neutrons conformément aux nouvelles recommandations de la Commission Internationale de Protection Radiologique (CIPR-103). Les fonctions de réponse de PN3 et Neutrak, associés avec des convertisseurs adaptés, ont été étudiés en les irradiant par des neutrons du calibrateur Am-Be de l'IPHC (Institut Pluridisciplinaire Hubert Curien), aux protons de 1 à 3 MeV de l'accélérateur Van de Graaff de l'INESS (INstitut d'Electronique du Solide et des Systèmes) et par des neutrons de référence thermiques et rapides auprès des installations de l'IRSN (Institut de Radiologie et de Sûreté Nucléaire). En dosimétrie neutronique, nous avons pu reproduire les résultats d'un test d'intercomparaison pour des neutrons rapides organisé par l'IRSN qui a validé nos mesures expérimentales, ce qui a permis de les appliquer aux neutrons thermiques. Un prototype de dosimètre neutrons basé sur la détection des thermiques a été testé avec succès au calibrateur de l'IPHC. Nous avons ainsi pu démontrer la faisabilité d'un dosimètre pouvant discriminer la contribution des neutrons thermiques des neutrons rapides par des convertisseurs chargés en bore BE10 et BN1. Les étalonnages de PN3 par des protons et des particules alpha permettraient de reconstituer le spectre en énergie des neutrons et de déterminer la dose associée.En métrologie radon, l'étalonnage de CR-39 dans une chambre à 222Rn a fourni une valeur de 0,12±0,02tr.cm-2.j-1.Bq-1.m3. Elle a été comparée à la valeur 0,13 tr.cm-2.j-1.Bq-1.m3 obtenue par simulation Monte Carlo à l'aide du code MCNPX. Comme application, la concentration et la dose effective annuelle du radon ont été déterminées pour la première fois dans des habitats de Bamako. Toutes les valeurs obtenues se trouvent dans les limites de sécurité recommandées par la CIPR. Également pour la première fois, des mesures par spectrométrie gamma et par contact radiographie ont été réalisées sur des échantillons de sol malien. Les activités massiques mesurées pour les régions de Ségou, Sikasso, Bamako et Kayes se trouvent dans la gamme de 19,9 à 132 Bq.kg-1.
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Vismara, Marcus Vinícius Gonçalves. "Estudo das propriedades dosimétricas de polímeros conjugados /." Bauru : [s.n.], 2011. http://hdl.handle.net/11449/99657.
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Resumo: Este trabalho teve como objetivo a investigação da interação de radiação gama com três polímeros: o polímero Poli(2-metóxi, 5-(2'-etil-hexilóx)-1,4- fenileno vinileno) (MEH-PPV)n e os polímeros solúveis em água Poly {[2,5-bis(2-(N,N-diethylamino)ethoxy) -1,4 -phenylene]-alt-1,4-phenylene} e o Poly [(2,5-bis (2 - (N,N - diethylammonium bromide) ethoxy) - 1,4 -phenylene) - alt - 1,4-phenylene]. O polímero MEH-PPV foi dissolvido nos solventes orgânicos clorofórmio e bromofórmio, já os outros dois polímeros, em água destilada e solução de HCI 1M. As amostras foram preparadas em várias concentrações e irradiadas com doses que variaram desde 0,01 Gy, sendo que cada amostra foi irradiada com apenas uma dose. Os resultados foram avaliados com técnicas espectroscópicas, sendo elas, espectroscopia de absorção óptica UV-visível e espectroscopia de fluorescência. Foi avaliada a alteração na posição do pico principal de absorção óptica com a dose absorvida pelas amostras. Como resultado principal, observou-se que os polímeros solúveis em água não apresentam alteração espectral após serem irradiados. Não sendo interessante para aplicação dosimétrica. Já para as amostras do polímero MEH-PPV diluídas em bromofórmio apresentaram alta sensibilidade para doses inferiores a 1 Gy, e apresentaram certa linearidade com a dose recebida (fator importante para aplicação dosimétrica). Para as amostras em clorofórmio, não foi observado deslocamento significativo do escpectro de absorção para doses inferiores a 1 Gy. No entanto para doses de 1 Gy à 90 Gy, o comportamento observado pode ser descrito por duas regiões lineares: uma com maior inclinação da reta para doses até cerca 30 Gy, e outro com inclinação da reta menor para doses entre 30 Gy e 90 Gy. O comportamento linear, assim como a inclinação da reta, do deslocamento da posição... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: The subject of this work is the investigation of gamma radition interaction with tree polymers: the polymer Poli(2-metóxi, 5-(2'-etil-hexilóx)-1,4- fenileno vinileno) (MEH-PPV)n e os polímeros solúveis em água Poly {[2,5-bis(2-(N,N-diethylamino)ethoxy) -1,4 -phenylene]-alt-1,4-phenylene} e o Poly [(2,5-bis (2 - (N,N - diethylammonium bromide) ethoxy) - 1,4 -phenylene) - alt - 1,4-phenylene]. The MEH-PPV polymer was dissolved in organic solvents, choloroform and bromoform, the other two polymers in distilled water and 1 M aqueous HCI solution. The samples were prepared at various concentrations and irradiated with doses ranging from 0.01 Gy to 90 Gy. The results were evaluated by spectroscopic techniques, which were, UV-visible absorption spectroscopy and fluorescence spectroscopy. They were evaluated the changes in the position of main optical absorption peak with the dose absorbed by the samples. As main result, it was observed that water-soluble polymers did not show spectral change after being irradiated. For dosimetric application this results are not interesting. For the MEH-PPV polymer samples diluted in bromoform presented highly sensitive to doses below 1 Gy, and showed some linearity with the dose received. For samples in chloroform, doses below 1 Gy did not showed significant shift in the absorption spectra. However, the samples irradiated with doses from 1 Gy to 90 Gy, the behavior can be described by two linear regions: one with a higher slope for doses up to about 30 Gy, and another with a lower slope for doses between 30 Gy and 90 Gy. A greater slope to doses up to about 30 Gy, and another with lower slope to doses between 30 and 90 Gy. The linear behavior and the slope of the main peak position is a important factor for dosimetric application. At the same time, a study of stability of the samples was performed. It was observed that the MEH-PPV samples in bromoform... (Complete abstract click electronic access below)
Orientador: Carlos Frederico de Oliveira Graeff
Coorientador: Marco Antonio Rodrigues Fernandes
Banca: Armando Beltran Flors
Banca: Antonio Ricardo Zanatta
O programa de Pós graduação em Ciência e Tecnologia de Materiais, PosMat, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp
Mestre
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Goulet, Mathieu. "Application of tomography techniques to plastic scintillation dosimetry." Thesis, Université Laval, 2014. http://www.theses.ulaval.ca/2014/30599/30599.pdf.
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Cette thèse porte sur le développement d’outils de contrôle de qualité pour les traitements de radiothérapie externe. Le but principal vise à incorporer les principes de tomographie à la dosimétrie par scintillateurs plastiques pour concevoir des appareils de haute résolution spatiale et faciles d’utilisation, tout en étant justes et précis. Dans un premier temps, la réponse de longues fibres scintillantes placées dans un champ de radiation est étudiée, et un détecteur de fluence est développé pour la validation en temps réel des traitements de radiothérapie. En utilisant l’information des deux extrémités de chaque fibre simultanément, la position de l’interaction du champ ainsi que l’intégrale de la fluence traversant la fibre peuvent être mesurées, permettant la détection d’erreurs de lames d’au moins 2 mm à l’isocentre. Le modèle théorique de réponse précédemment développé est ensuite appliqué à la reconstruction tomographique d’une distribution de dose mesurée à l’aide d’une matrice rotative de longues fibres scintillantes parallèles. Le dosimètre 2D obtenu parvient à reconstruire la dose calculée par le système de planification de traitement avec un écart maximal de 2% dans les régions de bas gradient de dose. Le concept de dosimétrie tomographique, ou tomodosimétrie, est ensuite appliqué à la mesure de dose en trois dimensions en utilisant des plans de fibres cylindriques et concentriques. En simulant la rotation de ces plans autour de leur axe central et en interpolant en trois dimensions les doses 2D obtenues, le dosimètre 3D parvient à reconstruire la dose de départ à un écart d’au plus 1% en dehors des zones de haut gradient de dose. Finalement, les principes de reconstruction itérative démontrés pour les longues fibres scintillantes sont appliqués à un volume de scintillateurs imagé à l’aide d’une caméra plénoptique. En re-projetant les projections acquises par les pixels de la caméra dans le volume de scintillateurs, le dosimètre 3D parvient à reconstruire en temps réel la dose à un écart d’au plus 3% dans les régions de faible gradient de dose. Cette étude conclut que le mariage de la tomographie et de la dosimétrie permet l’apparition d’une nouvelle génération d’appareils de contrôle de qualité alliant à la fois résolution spatiale et facilité d’utilisation.This thesis deals with the development of tools for the quality assurance of external beam radiotherapy. The main goal is to incorporate tomography processes to plastic scintillator dosimetry in order to conceive high resolution, precise, accurate and easy-to-use quality assurance devices. First, a long scintillating fiber response to an incoming radiation field is studied, and a fluence monitoring device is developed for the real-time validation of radiotherapy treatments. Using the light signal emitted from both sides of each fiber, both the interaction position of the incoming field and the fluence integral across the fiber can be measured, allowing for the detection of leaf errors of at least 2 mm at isocentre. The theoretical response model previously developed is then applied to the tomographic reconstruction of dose distributions measured using a rotating matrix of long scintillating fibers. The dose reconstructed using this 2D dosimeter is in agreement with the calculations from the treatment planning software up to a maximum difference of 2% in the low dose gradient regions. The concept of tomographic dosimetry, or tomodosimetry, is then applied to 3D dose measurements using concentric, cylindrical planes of fibers. By simulating the rotation of these planes around the dosimeter central axis and by interpolating in three dimensions the obtained 2D doses, the 3D dosimeter is able to reconstruct the initial input dose with a deviation of maximum 1% outside of high dose gradient regions. Finally, the iterative reconstruction principles demonstrated for long scintillating fibers are applied to a scintillator volume imaged using a plenoptic camera. By re-projecting the projections acquired by the camera sensor pixels inside the scintillator volume, the 3D dosimeter is able to reconstruct the dose in real time with a maximal deviation of 3% in the low dose gradient regions. This study concludes that the union of tomography and dosimetry enables the development of a new generation of quality assurance devices, combining both spatial resolution and user-friendliness.
Tableau d'honneur de la FÉSP
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Ritter, Birgit [Verfasser]. "The mobile dosimetric telescope : a small active dosimeter for the application in space ; development, calibration and measurements / Birgit Ritter." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/104218562X/34.
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Wai, Philip. "The application of 3-d dosimetry in brachytherapy treatment." Thesis, University of Surrey, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504948.
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In the UK, prostate cancer is the second most commonly occurring cancer in men.. The number of prostate cancer incidents is expected to increase due to improved screening and diagnostic techniques, whilst the mortality rate continues to fall as the variety ofavailable treatments increases. This research focuses on the commonly used brachytherapy seed OncoSeed Model 6711 manufactured by GE Healthcare. lodine-125 seeds are surgically implanted and left inside the prostate permanently to obtain local control of the malignant prostate cancer. Prior to the surgical procedure, a treatment plan is created on a computer planning system. There is currently no 3-D method to verify whether the planning system model matches the actual delivery ofradiation dose to the prostate. This study is presented as a typical case study of what can be achieved using solid polymer dosimetry. Experimental results are presented comparing solid polymer dosimetry using Optical-CT with radiochromic films (RCF) and Monte Carlo simulations. Initial Optical-CT results have shown good agreement to Monte Carlo, radiochromic films and comparable to previously published data.
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Hedtjärn, Håkan. "Dosimetry in brachytherapy : application of the Monte Carlo method to single source dosimetry and use of correlated sampling for accelerated dose calculations /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/med790s.pdf.
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Donovan, Ellen Mary. "Application of radiation physics to improve dosimetry in early breast cancer radiotherapy." Thesis, Institute of Cancer Research (University Of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417317.
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Dardaillon, Rémi. "Fibres optiques passives et actives sous irradiation : application à l'amplification et à la dosimétrie en environnement spatial." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS052/document.
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Les fibres dopées erbium couvrent de nombreuses applications, particulièrement dans le domaine des télécommunications terrestres et sous marines, avec les amplificateurs optiques. Aujourd’hui, il existe un réel intérêt pour l’industrie spatiale d’utiliser ces fibres dans les satellites. Cependant, pour utiliser leur potentiel, une qualification en milieu radiatif doit être effectuée, c'est justement l'objet principal de ce travail de thèse. Grâce au partenariat industriel avec Draka-Prysmian, nous avons accès à une grande diversité de fibres en termes de compositions chimiques : ceci nous permet d’étudier leur sensibilité aux radiations, et de comprendre le rôle essentiel des dopants et des codopants dans cette sensibilité. Une étude de celle-ci en temps réel, associée à une caractérisation pré et post-irradiation des fibres optiques, rend possible l'identification fine des défauts induits sous irradiation, et la compréhension de leur mécanisme de formation, en fonction de la composition de ces fibres. Cette étude permet ainsi de proposer un modèle physique de leur dégradation, et aussi de leur guérison, complété par un modèle d'amplificateur. Il permet de prédire, en fonction de la composition des fibres, le comportement quantitatif des amplificateurs optiques associés, en termes de gain et et de bande passante, versus un dépôt de dose typique d'une mission spatiale ; il répond ainsi aux attentes des principaux acteurs du domaine. En outre, le bénéfice de ce travail ouvre des portes dans le domaine de la dosimétrie par fibre optique active, dans différents environnements radiatifs autres que le domaine spatial, tels que le milieu médical ou l'environnement nucléaireErbium-doped optical fibers open up many applications, especially in the field of terrestrial and underwater telecommunications, with optical amplifiers. Nowadays, there is a real interest for the space industry to use these fibers in satellites. However, in order to use their full potential, qualification in radiative environments is to be carried out, this is the main focus of this PhD work. Thanks to the partnership with Draka-Prysmian group, we have a full access to a large diversity of specialty fibers, in terms of chemical compositions : this allows us to study their sensitivity to radiations, and to determine the important role of dopants and co-dopants in this sensitivity. A real-time study of it, associated with a qualification of pristine and irradiated optical samples, enables the detection of radiation-induced defects, and the understanding of their creation process, as a function of the fiber structure. This study provides a physical model describing the degradation and the recovery of these fibers, enhanced with an amplifier modeling. It allows the prediction of the quantitative behavior of specialty fiber-based amplifiers, in terms of gain and bandwidth, versus the chemical composition of the fibers used, for a typical space mission dose ; thus this modeling meets the needs of the spatial market key actors. Furthermore, the benefit of this work opens up another avenues for some larger opportunities, in various radiative environments, such as the medical field or the areas of nuclear facilities
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Flux, Glen David. "Multimodality image registration and its application to the dosimetry of intralesional radionuclide therapy." Thesis, Institute of Cancer Research (University Of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294908.
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Kouroukla, Eftychia. "Luminescence dosimetry with ceramic materials for application to radiological emergencies and other incidents." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11362/.
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The likelihood of the occurrence of radiological accidents which can induce significant health consequences to the members of the public has raised the importance of developing a personal radiation dosimetry system applicable to populations not monitored by dedicated dosemeters. Mobile phones are personal devices with high ubiquity and great potential for accident dosimetry applications. Alumina surface mount resistors (SMRs) are abundant in the printed circuit board of mobile phones and their potential as fortuitous dosemeters has been investigated using thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques. The physical mechanism of the generation of luminescence of the alumina SMRs is, however, less known. The basic luminescence defects in SMRs were identified to be F-type centres and their emission process was shown to be temperature dependent and highly quenched at room temperature (RT). The trap environment of beta irradiated SMRs includes a series of closely spaced traps covering thermal depths between 0.9-1.4 eV; predicting an average lifetime for thermal fading at RT of ca 23 years. Trapped charges evicted by thermal or optical stimulation are likely to recombine at F-type centres and contribute to the luminescence response that is likely to be thermally assisted via the vibrational modes of the lattice. A phonon-assisted de-excitation of the trapped charge population could additionally be involved in the mechanism of athermal or anomalous fading. Based on the temperature dependence of the rate of fading, a model is presented for the anomalous fading observed where phonon-assisted and tunnelling effects alternate or operate simultaneously depending on the temperature of the material. A number of aspects related to the use of SMRs in dosimetry seem to benefit from the investigation of the physical processes, although for accurate dose reconstruction it is imperative to know the energy of the ionising radiation source and the position of the mobile phone relative to the direction of the source. For example, at low-energy exposures the dose may be over-estimated, not only due to the non-flat energy response of the alumina, but also due to the presence of several parts of the mobile phone which can increase the amount of energy deposited in alumina substrates due to backscatter effects. In addition, MCNP simulations indicated that for low-energy exposures, such as for 192Ir, differences of up to an order-of-magnitude between resistor and whole body dose are expected. Finally, to specify the most appropriate dose conversion coefficients that can be applied to estimate whole body dose from OSL / TL determinations, the knowledge of the exposure geometry is crucial.
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Kwa, William. "Asymmetric collimation : dosimetric characteristics, treatment planning algorithm, and clinical applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq27182.pdf.
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Alaamer, Abdulaziz. "Quantification in single photon emission computed tomography and its application to targeted radiotherapy and dosimetry." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296162.
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Jafari, Shakardokht. "Characterisation and novel applications of glass beads as dosimeters in radiotherapy." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/808112/.
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The intent of external beam radiotherapy is to deliver as high a radiation dose as possible to tumour volume whilst minimizing the dose to surrounding normal tissues. Recent development of techniques such as intensity modulated radiation therapy (IMRT) and stereotactic ablative body radiotherapy (SABR) aim to extend this capability. The main feature of these techniques is to use beams which often contain small fields and very steep dose gradients. These present several dosimetric challenges including loss of charge particle equilibrium (CPE), partial occlusion of the direct-beam source and steep fall-off in dose in the penumbra. Dosimeters which are small in size relative to the radiation field dimensions are recommended for such conditions. The particular glass beads studied herein have several potentially favourable physical characteristics; they are small in size (1 to 3 mm diameter), chemically inert, inexpensive, readily available and reusable. The dosimetric characterisation of glass beads has been obtained by irradiating them in various radiotherapy beams of kilo-voltage and mega-voltage photons, megavoltage electrons, protons and carbon ions. They exhibit minimal fading compared with commercial LiF thermo-luminescent (TL) dosimeters, have high TL light transparency, high sensitivity and a large dynamic dose range that remains linear from 1 cGy to 100 Gy They have also been shown to be independent of dose rate and beam incidence angle, as well as having a low variation in response with energy over a range of megavoltage photon and electron beams. The latter characteristic is of importance, where spectral changes may occur as a function of field size and off axis location and for the use of dosimeters in postal audit situations where each institution may have slightly different quality index (QI) for their respective photon energies thus ensuring that the calibration is still valid. These properties suggest their practical use as TL dosimeters for radiotherapy dosimetry. Investigations have been performed to evaluate the feasibility of using glass beads in treatment plan verification, small field radiation dosimetry and postal dosimetry audit.
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Hochman, Mark Brett McEwen. "The application of artificial thermoluminescence to uranium exploration and uranium ore genesis studies." Title page, abstract and contents only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phh6825.pdf.
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Bose, Rajiv. "The development of an in-vivo dosimeter for the application in radiotherapy." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/7173.
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The expectation for continual improvements in the treatment of cancer has brought quality assurance in radiotherapy under scrutiny in recent years. After a cancer diagnosis a custom treatment plan is devised to meet the particular needs of the patient's condition based on their prognosis. A cancer treatment plan will typically comprise of several cancer treatment technologies combining to form a comprehensive programme to fight the malignant growth. Inherent in each cancer treatment technology is a percentage error in treatment accuracy. Quality assurance is the medical practice to minimise the percentage error in treatment accuracy. Radiotherapy is one of the several cancer treatment technologies a patient might receive as part of their treatment plan, and in-vivo dosimetry is a quality assurance technology specifically designed to minimise the percentage error in the treatment accuracy of radiotherapy. This thesis outlines the work completed in the design of a next generation dosimeter for in-vivo dosimetry. The proposed dosimeter is intended to modernise the process of measuring the absorbed dose of ionising radiation received by the target volume during a radiotherapy session. To accomplish this goal the new dosimeter will amalgamate specialist technologies from the field of particle physics and reapply them to the field of medical physics. This thesis describes the design of a new implantable in-vivo dosimeter, a dosimeter comprising of several individual stages of electronics working together to modernise quality assurance in radiotherapy. Presented within this thesis are the results demonstrating the performance of two critical stages for this new dosimeter, including: the oating gate metal oxide field effective transistor, a radiation sensitive electronic component measuring an absorbed dose of radiation; and the micro antenna, a highly specialist wireless communications device working to transmit a high frequency radio signal. This was a collaborative project between Rutherford Appleton Laboratory and Brunel University. The presented work in this thesis was completed between March 2007 and January 2011.
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Manescu, Petru-Stefan. "Continuum description of deformable organs based on tetrahedral meshes : application to dosimetry and imaging for hadron therapy." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10188.
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Dans le cadre du projet européen ENVISION (2010-2014) et en collaboration avec l'équipe CAS-PHABIO de l'IPNL, cette thèse constitue une contribution méthodologique et technique dans le domaine de la dosimétrie et de l'imagerie de contrôle par émission des positons (TEP) pour les organes en mouvement. Les méthodes actuelles utilisent le recalage déformable d'images CT pour estimer le mouvement des organes internes. Le recalage déformable permet d'estimer le déplacement de chaque voxel d'une image à une autre. La dose radio-thérapeutique ainsi que l'activité TEP sont accumulées sur des voxels. Ces approches ont des difficultés quand il s'agit de prendre en compte la variation de densité à l'intérieur des organes et l'aspect non-répétitif du mouvement respiratoire. Les travaux antérieurs de l'équipe ont permis de développer un premier modèle biomécanique complet du système respiratoire qui, corrélé avec des signaux externes, pourrait prendre en compte la variabilité du mouvement respiratoire. Cette thèse présente une approche qui permet d'intégrer un tel modèle biomécanique dans un système de planification de traitement pour l'hadronthérapie. Dans cette thèse, nous avons choisi d'investiguer de près l'utilisation des maillages tétraédriques déformables dans la dosimétrie et la reconstruction d'images TEP afin d'estimer les avantages et inconvénients de ce type de géométrie. En conclusion, notre approche peut être utilisée avec n'importe quel modèle de déformation basé sur une géométrie tétraédrique et dont le mouvement est décrit par le déplacement des nœuds des maillages et donc contrairement aux méthodes basés images, notre approche n'est pas nécessairement dépendante de l'existence des images internes à tout moment. Dans le futur, les méthodes développées dans cette thèse pourraient être utilisées avec un modèle biomécanique complet du système respiratoire afin de quantifier, par exemple, les effets de la variabilité de la respiration sur le dépôt de doseRespiratory-induced organ motion is a technical challenge to nuclear imaging and to charged particle therapy dose calculations for lung cancer treatment in particular. Internal organ tissue displacements and deformations induced by breathing need to be taken into account when calculating Monte Carlo dose distributions as well as when performing tomographic reconstructions for PET imaging. Current techniques based on Deformable Image Registration (DIR) cannot fully take into account the density variations of the tissues nor the fact that respiratory motion is not reproducible. As part of the ENVISION (2010-2014) European project, in collaboration with the CAS-PHABIO team from IPNL (the Nuclear Physics Institute from Lyon), this PhD project presents a methodological contribution to physical dose calculations and PET-based treatment verification for hadron therapy in the case of moving tumours. Contrary to DIR-based methods where motion is described by relative voxel displacement, each organ is represented as a deformable grid of tetrahedra where internal motion is described by mesh vertex transformations calculated using continuum mechanics. First, this PhD project proposes a new method to calculate four dimensional dose distribution over tetrahedral meshes, which are deformed using biomechanical modeling based on Finite Element Analysis (FEA). The second part of the PhD is focused on motion compensation for PET image reconstruction using deformable tetrahedral meshes
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Eivazi, Mohammad Taghi. "The application of experimental microdosimetric techniques to the dosimetry of X-rays in the diagnostic energy range." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238708.
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Schmitz, Tobias [Verfasser]. "ESR-dosimetry in thermal and epithermal neutron fields for application in Boron Neutron Capture Therapy / Tobias Schmitz." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/1112150870/34.
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CHAILLOU, STEPHANE. "Le sous maillage dans la fdtd application a la dosimetrie des radiotelephones." Paris 6, 1999. http://www.theses.fr/1999PA066099.
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Cette etude, realisee au centre national d'etudes des telecommunications (cnet), est consacree a la dosimetrie des radiotelephones. Il s'agit de mettre en uvre des techniques capables de quantifier l'energie deposee dans les tissus de la tete d'un utilisateur de radiotelephone. Dans une premiere partie, la methode fdtd (finite difference in time domain) et les divers outils developpes pour repondre specifiquement a cette problematique d'un point de vue numerique, sont presentes. Dans le but d'ameliorer les modeles utilises, une technique de sous maillage appliquee a la fdtd a ete developpee. Cette technique accroit localement dans un facteur 8 la resolution du maillage ce qui permet une meilleure description des antennes filaires qui composent les radiotelephones et d'augmenter, notamment, la definition dans certaines parties de la tete qui se trouvent proches de la source de rayonnement. Dans une deuxieme partie, diverses applications liees a la dosimetrie ont ete presentees en s'appuyant sur la fdtd et en particulier dans le cas d'un maillage non uniforme. Pour ameliorer le modele de telephone, nous avons cherche a modeliser une antenne helicoidale correspondant a un modele commercial qui equipe certains terminaux actuels. La difficulte principale mise en evidence est la prise en compte des interactions entre les spires juxtaposees. La derniere partie de cette etude est consacree a la dosimetrie experimentale qui s'inscrit comme une methode de validation des methodes numeriques mais surtout comme une methode complementaire. La solution numerique permet de prendre en compte un modele de tete reelle alors que l'experimentation permet de prendre en compte un telephone reel. Cette etude doit servir de support technique dans les debats menes autour des questions sanitaires qui se posent actuellement a propos des radiotelephones.
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Rahmanian, Shirin [Verfasser], and Oliver [Akademischer Betreuer] Jäkel. "Application of Fluorescent Nuclear Track Detectors for Cellular Dosimetry in Ion Beam Radiotherapy / Shirin Rahmanian ; Betreuer: Oliver Jäkel." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1210490064/34.
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Bush, Daniel A. "Application of luminescence dating to the study of archaic age anthropogenic mounds from the Lower Mississippi River Valley /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/6417.
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Mandelli, Elena. "Ionizing radiation detectors and their innovative application in proton therapy." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21880/.
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Through this thesis we wanted to present a branch of radiotherapy that uses proton beams to destroy tumors, namely proton therapy.
This technique, although relatively new (1946), is rapidly spreading thanks to the advantage of being able to precisely locate the release of the therapeutic dose of radiation.
After a brief presentation of the discovery of ionizing radiations’ history and their possible applications, we focused on the study of the protons’ behavior when they interact with matter, going to show why they are so advantageous, by studying different quantities such as stopping power, flow rate, flow rate variation, multiple coulomb scattering and proton RBE.
In fact, proton therapy represents a new and important therapeutic approach that allows a large part of healthy tissue to absorb less dose than in conventional therapies that use photons or electrons.
The most interesting aspect of this thesis, and still with a broad future perspective, concerns the different types of detectors used in this therapy, which play a fundamental role in the progress of nuclear medicine, leading to ever better methods of prevention, diagnosis and treatment of illnesses.
The future goal of this therapy is to develop new detectors, that are more equivalent to human tissues, both in behavior and detections, in order to obtain always better performances.
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Zhou, Yang. "Development of a CMOS pixel sensor for embedded space dosimeter with low weight and minimal power dissipation." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAE021/document.
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Cette thèse porte sur le développement d'un capteur de pixel monolithique CMOS utilisé pourl’identification et le comptage des particules ionisés dan l’espace avec un flux élevé. Un nouveauconcept pour l’identification de l’espèce des particules proposé dans la présente étude, est basésur l'analyse des amas de particules déclenchés. Pour valider ce nouveau concept, un capteur detaille complet, qui comprend la matrice de pixel sensible aux particules ionisés signal, une chaînede traitement du signal analogique, un convertisseur analogue numérique de 3 bits, et untraitement du signal numérique a été conçu dans un processus de 0.35 μm. Le capteur sortiedirectement des informations de flux à travers 4 canaux avec un débit de données très faible(80 bps) et dissipation d’énergie minimale (~ 100 mW). Chaque canal représente particules avecdifférentes espèces et les énergies. La densité maximum de flux mesurable est jusqu'à 108particules/cm2/s (coups s'accumulent < 5%). Un prototype à échelle réduite a été fabriqué et testéavec trois types d'illumination de rayonnement (rayons X, les électrons et laser infrarouge). Tousles résultats obtenus valident le nouveau concept proposé. Un moniteur de rayonnement spatialtrès miniaturisé basé sur un capteur de pixel CMOS peut être prévu. Le moniteur peut présente lesmêmes performances que les compteurs actuels, mais avec une dissipation de puissance réduited'un ordre de grandeur qu'un poids, un volume d'encombrement et un coût moindre. En outre, enraison de ses sorties de haut niveau et faible débit de données, aucune traitement supplémentairedu signal dehors du capteur est nécessaire, ce qui le rend particulièrement attrayant pour desapplications dan les petits satellitairesThis thesis focuses on the development of a CMOS monolithic pixel sensor used for space ionizingparticles identification and counting in high flux. A new concept for single particle identification isproposed in this study, which is based on the analysis of particle triggered clusters. To validate thisnew concept, a full size sensor including the sensitive pixel matrix, an analogue signal processingchain, a 3-bit analogue to digital converter, and a digital processing stage was designed in a 0.35μm process. The sensor directly output particles flux information through 4 channels with a verylow data rate (80 bps) and minimal power dissipation (~ 100mW). Each channel representsparticles with different species and energies. The highest measurable flux density is up to 108particles/cm2/s (hits pile up < 5%). A reduced scale prototype was fabricated and tested with 3types of radiation illumination (X-ray, electrons and infrared laser). All the results obtained validatethe proposed new concept and a highly miniaturized space radiation monitor based on a singleCMOS pixel sensor could be foreseen. The monitor could provide measurements of comparable orbetter quality than existing instruments, but at around an order of magnitude lower powerconsumption, mass and volume and a lower unit cost. Moreover, due to its high level and low datarate outputs, no signal treatment power aside the sensor is required which makes it especiallyattractive for small satellite application
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Allard, Thierry. "La kaolinite : un dosimetre des rayonnements naturels application au tracage de migrations anciennes de radioelements dans la geosphere." Paris 7, 1994. http://www.theses.fr/1994PA077114.
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La kaolinite, un mineral argileux frequent a la surface de la terre, peut memoriser la presence ancienne de radioelements. Elle contient en effet des defauts crees par les rayonnements naturels et stables a l'echelle des temps geologiques: les centres a, detectes par resonance paramagnetique electronique. Cette these definit les potentialites du dosimetre kaolinite pour l'etude de migrations anciennes d'uranium dans la geosphere. Dans une premiere partie, on a irradie des kaolinites naturelles de reference avec des rayonnements alpha et gamma dans un vaste domaine de doses compatibles avec les geosystemes de la surface de la terre. On a tenu compte de la variabilite naturelle des kaolinites en termes de desordre cristallin et d'impuretes chimiques (fe#3#+) ou mineralogiques (illite, smectite). On montre que la courbe de dosimetrie du centre a peut etre definie par une fonction exponentielle dependant de deux parametres (la valeur de la concentration a saturation et le coefficient d'efficacite) qui sont correles entre eux. Ces parametres de dosimetrie sont aussi correles au degre d'ordre cristallin local des kaolinites, ce qui suggere la possibilite de les estimer par une simple mesure du desordre cristallin. Dans une seconde partie, on utilise ces resultats experimentaux pour estimer les paleodoses de kaolinites prelevees dans deux gisements d'uranium tertiaires, consideres comme analogues naturels de sites de stockage de dechets radioactifs a haute activite. On montre qu'il est possible de quantifier des pertes ou accumulations anciennes d'uranium, sous reserve de determiner prealablement (i) l'age des kaolinites et les periodes de fonctionnement de l'alteration (ii) les contributions des radiosources comme #2#3#2th, #4#0k et rayons cosmiques (la partie residuelle de la paleodose etant due a l'uranium) (iii) un modele de mobilite de l'uranium (perte/accumulation ponctuelle ou continue) realiste par rapport a l'histoire geochimique du site
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Nefzi, Amani. "Analysis and dosimetry of the coupling of electromagnetic waves with biological tissues : application to applicator design for biomedical and study of health effects." Thesis, Limoges, 2021. http://www.theses.fr/2021LIMO0011.
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L’évolution et l’utilisation croissante des systèmes de communications mobiles sont associées à des études en laboratoire pour s’assurer de l’innocuité d’une exposition aux ondes électromagnétiques radiofréquences. Dans ce contexte, ce mémoire se concentre sur la caractérisation de systèmes d'exposition permettant des études en laboratoire sur des modèles cellulaires in vitro. Une double approche, numérique et expérimentale, est mise en œuvre pour réaliser la dosimétrie de ces dispositifs, afin de déterminer et maîtriser les niveaux d’exposition. Une des problématiques liées à cette dosimétrie est due aux dimensions micrométriques mises en jeu. Aussi, une technique de microscopie basée sur un marqueur fluorescent dépendant de la température, nommé Rhodamine B, a été mise en place et évaluée. Il ressort de cette évaluation une recommandation sur la concentration du marqueur de l’ordre de 50 μM. Après calibration, il est alors possible d’estimer le débit d’absorption spécifique (DAS) à partir de la variation de température, et ce même pour de faibles niveaux de DAS (< W/kg) avec une résolution spatiale inférieure à la dizaine de micron. On parle alors de microdosimétrie. Les deux principaux systèmes d’exposition étudiés, basés sur des réseaux de microélectrodes (MEA), permettent l’enregistrement d’une activité électrophysiologie de neurones. L’exposition aux ondes électromagnétiques est réalisée simultanément en insérant ces MEA dans des cellules TEM. De la dosimétrie effectuée à 1.8GHz, il ressort une plus forte sensibilité du premier MEA à son environnement. On a montré que les modifications apportées au second MEA, taille de l’ouverture et plan de masse, ont permis de limiter de façon significative l’influence de l’environnement. La microdosimétrie a mis en évidence une bonne homogénéité du DAS entre les électrodes avec une valeur estimée à 7±1W/kg pour1W incident. Enfin, un dispositif d'exposition microfluidique basé sur un guide d'ondes coplanaire a été caractérisé en conditions statiquesThe evolution and increasing use of mobile communications systems was associated with laboratory investigations to study radiofrequency electromagnetic waves exposure safety. In this context, this thesis focuses on the characterization of exposure systems allowinglaboratory in vitro studies on cell models. A dual numerical and experimental approach is implemented to perform the devices dosimetry allowing to determine and control the exposure levels. One of the limitations associated with this dosimetry is due to the micrometric dimensions involved. Therefore, a microscopy technique based on a temperature-dependent fluorescent dye named Rhodamine B was set up and evaluated. This assessment recommends an optimal concentration of the dye at around 50 μM. After calibration, it is possible to estimate the specific absorption rate (SAR) from the temperature variation, even for low levels of SAR (< W / kg) with a spatial resolution of less than ten micrometers i.e. microdosimetry. The two main exposure systems studied, based on microelectrode arrays (MEA), allow the recording of neurons electrophysiological activity. Exposure to electromagnetic waves is achieved simultaneously by inserting these MEAs into TEM cells exposure systems. Dosimetry carried out at 1.8 GHz shows a higher sensitivity of one MEA to its environment. It was shown that the modifications made to the second MEA such as its aperture size and ground planes, have reduced the proximity environment influence. The microdosimetry demonstrated good homogeneity of the SAR between the electrodes with an estimated value of 7 ± 1 W / kgfor 1 W incident power. Finally, a microfluidic exposure device based on a coplanar waveguide was characterized under static conditions
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Cavallone, Marco. "Application of laser-plasma accelerated beams to high dose-rate radiation biology." Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX063.
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Le cancer est la deuxième cause de décès dans le monde, représentant environ un décès sur six en 2018. Parmi les techniques employées de nos jours dans la lutte contre le cancer, l’une des plus utilisées et prometteuses est la radiothérapie, technique consistant en l’utilisation de rayonnements ionisants afin de déposer de l’énergie dans la tumeur pour la traiter. Or, puisque les cellules saines sont également endommagées par les rayonnements, le but de la radiothérapie est d’augmenter la sélectivité du traitement en épargnant autant que possible les tissus sains. L’optimisation de la sélectivité repose sur plusieurs aspects, comprenant l’optimisation spatiale de la dose, la précision de l’imagerie et de la dosimétrie, le type de rayonnement et la structure temporelle utilisée pour délivrer la dose. En particulier, le rôle du débit de dose et du temps d’irradiation n’a pas encore été explorés en détail.Les accélérateurs cliniques délivrent la dose avec un débit de dose d’environ quelques Gy/min, ce qui entraîne des temps d’irradiation de l’ordre de quelques minutes. Si, d’une part, l’effet d’une réduction du débit de dose de l’ordre de cGy/min sur la réponse biologique est bien connu, d’autre part l’effet d’un débit de dose élevé doit encore être éclairci. Recemment, des études in vivo réalisées avec des électrons et des photons produits par des prototypes d’accélérateurs ont montré que l’administration de la dose dans un temps court (<500 ms) et à un débit de dose élevé (>40 Gy/s) augmente la sélectivité du traitement en réduisant le risque d’effets secondaires sur les tissus sains. Bien que les causes de ce phénomène soient encore à l’étude, le protocole FLASH a été testé avec succès sur le premier patient en 2019. Ces résultats soulignent l’importance de la structure temporelle de l’irradiation et les avantages potentiels que les protocoles d’irradiation à haut débit de dose peuvent apporter en clinique. Or, l’utilisation de ces protocoles demande une compréhension plus approfondie des processus physico-chimiques et biologiques déclenchés par un dépôt de dose rapide.Dans ce contexte, les faisceaux de particules accélérées par laser représentent un outil unique pour jeter de la lumière sur les processus qui régissent la réponse biologique suite à une irradiation à haut débit de dose. Ces faisceaux sont produits en focalisant une impulsion laser ultra-courte (~fs) et ultra-intense (1019 W/cm2) sur une cible mince solide ou gazeuse (~μm), ce qui produit des faisceaux de particules ayant une durée de l’impulsion allant de la picoseconde à la femtoseconde. Ces caractéristiques permettent d’atteindre un débit de dose dans l’impulsion de l’ordre de ~109 Gy/s, c’est-à-dire des conditions d’irradiation extrêmement différentes par rapport aux protocoles de traitement conventionnels et FLASH. Pour cette raison, les faisceaux de particules accélérées par laser ont reçu une grande attention au cours des dernières années, mais leur effet biologique est toujours en discussion et d’autres études plus approfondies sont nécessaires.Cette thèse décrit les atouts des Protons Accélérés par Laser (PAL) et des Électrons Accélérés par Laser (EAL) produits par différents types de laser à haute puissance disponibles dans le commerce. En particulier, elle présente des études expérimentales et théoriques réalisées avec trois types de faisceaux permettant différentes modalités temporelles d’administration de la dose. L’objectif est de traiter certains des principaux problèmes liés à l’application de ces sources de particules à la biologie des rayonnements et de montrer des solutions et des techniques viable pour mener des études de radiobiologie systématique. Cela demande une caractérisation précise de ces faisceaux, l’optimisation de la distribution de la dose dans la cible biologique à travers la conception de lignes de transport adaptées et, enfin, l’étude de la réponse des instruments de dosimétrie utilisés en clinique à haut débit de doseCancer is the second leading cause of death globally, accounting for an estimated 9.6 million deaths, or one in six deaths, in 2018. Besides surgery and chemotherapy, radiotherapy is one of the major treatment modality. It consists in the use of ionising radiation to kill cancerous cells by depositing energy into the tumour and destroying the genetic material that controls how cells grow and divide. While both cancerous and healthy cells are damaged by radiation, the goal of radiotherapy is to increase the treatment selectivity by sparing as much as possible the healthy tissues. Optimisation of the selectivity reposes on several aspects, including spatial optimisation of the dose, precision of imaging techniques and dosimetry instruments, use of different radiations and temporal structures of dose delivery. In particular, the role of the dose-rate and the total irradiation time has not been extensively explored yet.Clinical accelerators typically deliver the dose with a dose rate around few Gy/min, leading to exposure times in the order of few minutes to deliver a therapeutic dose. While the effect of a reduction of the dose rate in the order of cGy/min is well known, the effect of high-dose rate, fast irradiation on living cells still need to be elucidated. Evidences of an effect of the high dose-rate on the biological response have been recently observed in many studies. In particular, in-vivo studies performed with electrons and photons produced by accelerator prototypes have shown that delivering the prescribed dose in a short exposure time (<500ms) and at a high dose-rate (>40Gy/s) increases the treatment selectivity by reducing the occurrence of secondary effects on healthy tissues compared to conventional treatments with the same total dose. Although theoretical explanations underpinning such phenomenon are still under discussion, the so-called FLASH protocol has been successfully tested with the first human patient in 2019, paving the way for further research in this domain. These important results point out the importance of the dose delivery modality on the treatment selectivity and the potential benefit that high dose-rate protocols may bring to clinics, asking for a deeper understanding of the physico-chemical and biological processes following fast dose deposition.In this scenario, Laser-Driven Particle (LDP) beams represent a unique tool to shed some light on the radiobiological response following high-dose rate irradiation. LDP sources are produced by focusing an ultra-short (~fs) and ultra-intense (1019 W/cm2) laser pulse on a solid or gaseous thin target (~μm), producing proton and electron bunches with duration of respectively a few picoseconds and a few femtoseconds. These characteristics allow the reach of extremely high peak dose-rate in the pulse of the order of ~109 Gy/s in comparison with conventional and FLASH treatment protocols. For this reason, LDP sources have been receiving great attention in the last decade, but their radiobiological effect is still debated and further systematic studies are required.This thesis discusses the potential of both Laser-Accelerated Protons (LAP) and Laser-Accelerated Electrons (LAE) produced by different types of commercially available high-power lasers systems. In particular, it presents experimental and theoretical studies carried out with three different types of LDP beams, i.e. Hz LAPs, single-shot LAPs and kHz LAEs, enabling different temporal modalities of dose delivery. The goal is to address some of the main issues related to the application of such sources to radiation biology and show viable solutions and irradiation protocols to perform systematic radiobiology studies. Such issues include accurate characterisation of the source, optimisation of the dose distribution at the biological target through the design of adapted transport beamlines and investigation of the behaviour of dosimetric instruments for high dose-rate dosimetry
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Kamenopoulou, Vassiliki. "Proprietes dosimetriques des fibres textiles : application a la dosimetrie par resonance paramagnetique electronique d'un accident d'irradiation gamma." Toulouse 3, 1987. http://www.theses.fr/1987TOU30172.
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ALESSANDRI-FRACCARO, MARIE FRANCE. "Proprietes exoemissives et thermoluminescentes de l'alumine alpha : application a la dosimetrie des rayonnements ionisants en cas d'accident." Toulouse 3, 1989. http://www.theses.fr/1989TOU30088.
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Le travail expose comporte deux parties. Dans la premiere, plus fondamentale, on a mis en evidence un phenomene de phototransfert en emission exoelectronique thermostimulee (e. E. T. S. ). Dans la seconde partie, on s'interesse a l'application des proprietes dosimetriques de l'alumine alpha a la dosimetrie et la cartographie d'accident d'irradiation
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Parisi, A. "A new method using a dosimetric technique to evaluate ultraviolet spectra and doses for application to plants." Thesis, Queensland University of Technology, 1996.
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Brambilla, Andrea. "Application des semi-conducteurs couches minces a la detection de rayonnements nucleaires dans le cadre de la radioprotection." Paris 11, 1998. http://www.theses.fr/1998PA112103.
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Des detecteurs de rayonnement a base de diodes p-i-n en silicium amorphe hydrogene (a-si:h) et de couches de diamant polycristallin ont ete elabores par la technique de depot chimique en phase vapeur assiste par plasma. Les echantillons ont ete caracterises afin de determiner les proprietes physiques, optiques et electriques et d'optimiser les conditions de depot du point de vue de la detection de rayonnements. Les detecteurs ont ete testes sous rayonnements de maniere a determiner leurs performances en termes de sensibilite et de rapport signal sur bruit. Les mecanismes de collection des charges ont ete analyses. Dans les diodes p-i-n en a-si:h, l'effet du profil de champ electrique, du transport dispersif des trous et de la recombinaison des charges a ete etudie. Dans le diamant polycristallin, des mecanismes de recombinaison dans le volume des cristallites et au niveau des joints de grains ont ete mis en evidence. L'interaction de rayonnements , et dans les detecteurs a ete etudiee par simulation numerique avec un code de calcul monte carlo et par des mesures experimentales. Le faible pouvoir d'arret permet de detecter de maniere selective des particules chargees en presence d'un bruit de fond du au rayonnement. L'utilisation de diodes a-si:h minces de grande surface permet donc d'ameliorer la sensibilite de detecteurs pour des mesures de contamination surfaciques necessitant une bonne discrimination entre particules chargees et photons. La reponse dosimetrique des detecteurs sous photons ou electrons a ete simulee par la methode de monte carlo et comparee a celle d'un detecteur classique. Des mesures sous faisceau de references ont ete effectuees afin de valider les resultats obtenus par simulation. Le diamant, dont le numero atomique est proche de celui des tissus humains, est un bon materiau equivalent tissu et peut etre utilise pour la mesure de la dose sans apporter de corrections dues a l'energie des photons incidents.