Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-17T17:35:26Z No. of bitstreams: 0 / Made available in DSpace on 2017-11-17T17:35:26Z (GMT). No. of bitstreams: 0 / A utilização da técnica de teleterapia para tratamento de câncer tem sido usada por anos com bons resultados clínicos. Em meados da década de 90, a remoção do filtro aplainador, item que compõe o cabeçote de um acelerador linear de uso clínico, tem sido objeto de estudos por demonstrar bons resultados no tratamento de alguns tipos de câncer. Técnicas utilizadas como Radioterapia de Intensidade Modulada (IMRT) e Radioterapia Estereotáxica (SRT), mostram-se mais eficazes quando não se utiliza o filtro aplainador. A empresa Varian Oncology lançou em 2012 um acelerador linear de uso clínico capaz de operar com o filtro aplainador (FF) e sem o filtro aplainador (FFF), o TrueBeam. Os objetivos desse trabalho são avaliar a homogeneidade de dois importantes parâmetros utilizados para o cálculo de dose nos pacientes submetidos ao tratamento com esse modelo de acelerador linear, a porcentagem de dose profunda (PDP) e índice de qualidade do feixe (TPR20/10). Os dados fornecidos para a análise foram cedidos pelo Hospital Israelita Albert Einstein (HIAE), Real Hospital Português (RHP) e 3 instituições norte-americanas. Através de uma análise estatística dos dados das instituições citadas pode-se observar melhor o comportamento desses parâmetro que demonstraram-se muito homogêneos e com erros menores que 1% na maioria dos casos, confirmando desse modo que os aceleradores lineares do modelo TrueBeam mantém na maioria das vezes uma boa concordância dos parâmetros analisados. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Doses absorvidas e doses efetivas podem ser calculadas utilizando códigos computacionais de transporte de radiação. A qualidade desses cálculos depende dos dados nucleares, no entanto, são raras as informações sobre as diferenças nas doses causadas por diferentes bibliotecas. O objetivo desse estudo é comparar os valores de dose (absorvida e efetiva) obtidos utilizando diferentes bibliotecas de dados nucleares devido a uma fonte externa de nêutrons na faixa de 10-11 a 20 MeV. As bibliotecas de dados nucleares são: JENDL 4.0, JEFF 3.1.1 e ENDF/B-VII.0. Cálculos de doses foram realizados utilizando o código MCNPX considerando o modelo antropomórfico da ICRP-110. As diferenças nos valores das doses absorvidas utilizando as bibliotecas JEFF 3.1.1 e a ENDF/B.VII são pequenas, em torno de 1%, porém os resultados obtidos com a JENDL 4.0 apresentam diferenças de até 85 % compara aos resultados da ENDF/B-VII.0 e JEFF 3.1.1. Diferenças nas doses efetivas são em torno de 1,5% entre ENDF/B-VII.0 e JEFF 3.1.1, e 11 % entre ENDF/B-VII.0 e JENDL 4.0. / Absorbed dose and Effective dose are usually calculated using radiation transport computer codes. The quality of the calculations of absorbed dose depends on nuclear data utilized, however, there are rare information about the differences in dose caused by the use of different libraries. The objective of this study is to compare dose values obtained using different nuclear data libraries due to external source of neutrons in the energy range from 10-11 to 20 MeV. The nuclear data libraries used are: JENDL 4.0, JEFF 3.3.1 and ENDF/B.VII. Dose calculations were carried out with the MCNPX code considering the anthropomorphic ICRP 110 model. The differences in the absorbed dose values using JEFF 3.3.1 and ENDF/B.VII libraries are small, around 1%, but the results obtained with JENDL 4.0 presented differences up to 85% compared to ENDF and JEFF results. Differences in effective dose values are around 1.5% between ENDF and JEFF and 11% between ENDF/B.VII and JENDL 4.0.

Tissue heterogeneity effects present a major challenge to electron beam dosimetry in radiotherapy and radiation protection. The perturbation of the absorbed dose distribution in tissue due to the presence of heterogeneous material boundaries was investigated in this work. Experiments were conducted in a tissue-equivalent phantom in order to quantify electron backscatter from various materials. For these experiments, irradiations were performed using a 6MeV (nominal) electron beam under conditions of one dimensional geometry. Depth-energy degradation of the electron beam provided mean electron energies of 2.3MeV, 1.9MeV, and 1.4MeV at interface locations. Backscatter phenomena were investigated for the following interface geometries: polystyrene/air, polystyrene/cortical-bone-equivalent plastic, polystyrene/copper, and polystyrene/bismuth. Novel radiochromic film dosimetry techniques were developed for these experiments, and the dose and energy response characteristics of GAFChromic Type 37-041 film were investigated. Monte Carlo simulations of the experiments were performed in parallel, using tile ITS TIGER code, and methodologies were developed to determine appropriate input parameters to these simulations. From experimental and Monte Carlo results, the backscatter factor at the interface, its spatial variation with depth, and its dependence on electron energy and scatterer atomic number were investigated. / Thesis / Master of Science (MS)

The study is devoted to problems of exposure caused by radionuclides in construction materials. Results received by gamma measurements and calculations (dose modeling) are used. Construction materials produced and/or used in Lithuania were investigated. The results of measurements (concentrations of natural radionuclides and activity indexes) are given for different types of construction materials. On the basis of these results and peculiarities of use of construction materials they have been classified according to their radiological significance. It helps to determine possible amounts of construction materials to be investigated and priorities of investigations. Relationship between activity indexes of different construction materials and dose rates in premises constructed of these construction materials has been determined. It might be used for increase of precision of personal dosimetric measurements performed in premises constructed of different materials. Possible relationship between absorbed dose rate indoors and concentration of indoor radon is discussed. Results of measurements of concentrations of natural radionuclides in archeological samples of construction materials are also presented and discussed. Dose modeling has been performed with the help of ALARA planning tool Visiplan 3D. Distributions of absorbed dose rate in standard living premises have been determined, relationship between dose rate and different parameters of constructions, such as thickness... [to full text]

The study is devoted to problems of exposure caused by radionuclides in construction materials. Results received by gamma measurements and calculations (dose modeling) are used. Construction materials produced and/or used in Lithuania were investigated. The results of measurements (concentrations of natural radionuclides and activity indexes) are given for different types of construction materials. On the basis of these results and peculiarities of use of construction materials they have been classified according to their radiological significance. It helps to determine possible amounts of construction materials to be investigated and priorities of investigations. Relationship between activity indexes of different construction materials and dose rates in premises constructed of these construction materials has been determined. It might be used for increase of precision of personal dosimetric measurements performed in premises constructed of different materials. Possible relationship between absorbed dose rate indoors and concentration of indoor radon is discussed. Results of measurements of concentrations of natural radionuclides in archeological samples of construction materials are also presented and discussed. Dose modeling has been performed with the help of ALARA planning tool Visiplan 3D. Distributions of absorbed dose rate in standard living premises have been determined, relationship between dose rate and different parameters of constructions, such as thickness... [to full text]

<p>Neutron-carbon interactions have been studied with a focus on charged-particle production of relevance to radiation protection and medical applications, such as cancer therapy. The measurements have been performed using the particle-detection setup, MEDLEY, and the 96 MeV neutron beam at the The Svedberg Laboratory in Uppsala.</p><p>Double-differential cross sections of inclusive charged-particle production are compared with recent calculations from models based on the GNASH code including direct, preequilibrium and compound processes. For protons, the shapes of the cross-section spectra are reasonably well described by the calculations. For the other particles- <i>d</i>, <i>t</i>, ³He and α- there are important discrepancies, in particular for ³He-ions and α-particles, concerning both shape and magnitude of the spectra.</p><p>Using the new cross sections, partial as well as total KERMA coefficients have been determined. The coefficients have also been compared to previous experimental results and model calculations. The <i>p</i>, <i>d</i> and <i>t</i> KERMA coefficients are in good agreement with those from a previous measurement. For the helium isotopes, there are no previous measurements at this energy. The KERMA coefficients are considerably higher (by up to 30%) than those predicted by the calculations.</p><p>The KERMA results indicate that protons and α -particles are the main contributors to the dose. A 6x6x6 cm³ carbon phantom, exposed to a broad and a pencil-like beam, is used for the computation of the absorbed doses deposited by these two particles in spheres of 1 μm in diameter, located at various positions in the phantom. The maximum doses are deposited at ~3 cm from the surface of neutron impact for protons and within 1 cm for α-particles. For the pencil beam, deposited doses are spread over regions of ~1.5 cm and ~300 μm transverse to the beam for protons and α-particles, respectively. The results are consistent with previous integral measurements at lower energies.</p>

Neutron-carbon interactions have been studied with a focus on charged-particle production of relevance to radiation protection and medical applications, such as cancer therapy. The measurements have been performed using the particle-detection setup, MEDLEY, and the 96 MeV neutron beam at the The Svedberg Laboratory in Uppsala. Double-differential cross sections of inclusive charged-particle production are compared with recent calculations from models based on the GNASH code including direct, preequilibrium and compound processes. For protons, the shapes of the cross-section spectra are reasonably well described by the calculations. For the other particles- d, t, 3He and α- there are important discrepancies, in particular for 3He-ions and α-particles, concerning both shape and magnitude of the spectra. Using the new cross sections, partial as well as total KERMA coefficients have been determined. The coefficients have also been compared to previous experimental results and model calculations. The p, d and t KERMA coefficients are in good agreement with those from a previous measurement. For the helium isotopes, there are no previous measurements at this energy. The KERMA coefficients are considerably higher (by up to 30%) than those predicted by the calculations. The KERMA results indicate that protons and α -particles are the main contributors to the dose. A 6x6x6 cm3 carbon phantom, exposed to a broad and a pencil-like beam, is used for the computation of the absorbed doses deposited by these two particles in spheres of 1 μm in diameter, located at various positions in the phantom. The maximum doses are deposited at ~3 cm from the surface of neutron impact for protons and within 1 cm for α-particles. For the pencil beam, deposited doses are spread over regions of ~1.5 cm and ~300 μm transverse to the beam for protons and α-particles, respectively. The results are consistent with previous integral measurements at lower energies.

Les mesures fines des faibles radioactivités par la spectrométrie gamma nécessitent l’optimisation de la géométrie de détection et la connaissance du schéma de niveaux des raies gamma. Ainsi, on peut augmenter le taux de comptage et par conséquent, réduire l’incertitude statistique des pics spectraux exploités pour le calcul de l’activité des radio-isotopes en rapprochant le plus possible l’échantillon du détecteur. Cependant, l’augmentation du volume de l’échantillon demande une correction de l’auto-absorption des émissions par l’échantillon même, et le rapprochement du détecteur est à l’origine du phénomène de pic-somme. L’utilisation de MCNPX a permis de mettre en évidence les effets séparés de la densité de l’échantillon et le nombre atomique effectif dans l’atténuation des photons d’énergie inférieure à 100 keV. Les facteurs de correction du pic-somme sont obtenus par MCNPX, GESPCOR et ETNA. Ainsi, une base des données pour 244 radionucléides a été établie pour des géométries SG50 et SG500 au contact d’un détecteur. Dans une application à la radioprotection, des échantillons de matériaux de construction ont été analysés par la spectrométrie gamma. L’Uranium-238, le Thorium-232 et le Potassium-40 ont été identifiés et corrigés des effets sus-cités. La dosimétrie de leurs rayonnements gamma a permis d’évaluer les indices de risque, la dose absorbée et la dose efficace annuelle reçues provenant de ces matériaux. Les simulations par MCNPX corroborent le modèle de calcul de la dose absorbée. Il a permis aussi d'étudier la distribution de la dose dans les habitations de différentes dimensions. Les résultats obtenus sont en accord avec les limites règlementaires. / Precisely measuring weakly radioactive samples by gamma-ray spectrometry requires optimizing the detection geometry and knowledge of the gamma-ray decay scheme. One can thus increase the counting rate and reduce the statistical uncertainty of the spectral peaks used to determine radioisotope activities. However, an increased sample volume requires a correction for the self-absorption of y-rays in the sample itself, and approaching a sample to the detector gives rise to coincidence summing. MCNPX simulations permitted finding the separate influence of sample density and effective atomic number of the sample in the attenuation of photons with energies less than 100 keV. Peak-summing corrections were obtained with MCNPX, GESPCOR and ETNA. Thus a data base for 244 radionuclides could be established for SG50 and SG500 geometries in contact with a planar detector. In an application of the results to the health physics domain, construction materials were analyzed. Naturally-occurring Uranium-238, Thorium-232 and Potassium-40 activities were identified and corrected for the above-mentioned effects in order to evaluate the risk indexes, the absorbed dose and the annual effective dose received from different dimensions built of these materials. MCNPX simulations corroborated the model used to calculate the absorbed dose and gave its distribution in an enclosed space. The results obtained are within the recommended norms.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-03-21T19:51:42Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE FINAL versão digital.pdf: 2839254 bytes, checksum: 962b7ff83b975bcd276b612274de7368 (MD5) / Made available in DSpace on 2017-03-21T19:51:42Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE FINAL versão digital.pdf: 2839254 bytes, checksum: 962b7ff83b975bcd276b612274de7368 (MD5) Previous issue date: 2016-08-15 / Facepe / Dentre os diversos procedimentos intervencionistas com fins terapêuticos, a quimioembolização hepática tem se destacado por ser de alta complexidade e resultar em altas doses de radiação aos pacientes e à equipe médica. Em alguns casos, o paciente requer várias sessões para tratar a mesma lesão, o que aumenta a probabilidade de ocorrência de lesões na pele e/ou efeitos estocásticos. Embora seja uma técnica altamente utilizada no Brasil, a quimioembolização não tem sido alvo de estudos dosimétricos. Este estudo apresenta os resultados da avaliação dosimétrica realizada na equipe médica e pacientes durante 109 procedimentos de quimioembolização hepática, realizados em seis serviços de hemodinâmica na cidade de Recife, Pernambuco. Os procedimentos foram realizados utilizando equipamentos de angiografia digital de diferentes fabricantes e tecnologias. A dosimetria dos pacientes foi caracterizada através das estimativas da máxima dose na pele (MDP), do produto kerma ar-área (PKA) e do kerma ar de referência (Ka,r). A MDP foi estimada a partir da utilização de filmes radiocrômicos do tipo Gafchromic XR RV3. Para avaliar o risco de efeitos estocásticos, foi estimada a dose absorvida em órgãos a partir de simulações Monte Carlo utilizando fantomas antropomórficos femininos e masculinos da serie FASH e MASH. Os resultados da dosimetria com filme radiocrômico mostraram valores da MDP variando de 180 a 5650 mGy; sendo que 40% dos pacientes apresentaram valores de dose na entrada da pele que ultrapassaram o limiar de dose para ocorrência de eritema transitório, que é de 2 Gy. O estudo das correlações entre a MDP, PKA e Ka,r mostrou que o Ka,r pode ser utilizado para avaliar a possibilidade de ocorrência de reações tissulares na pele dos pacientes submetidos a procedimentos de quimioembolização. Os resultados das simulações mostraram que alguns órgãos internos dos pacientes podem receber doses entre 500 mGy e 1 Gy. A dosimetria ocupacional foi realizada utilizando dosímetros termoluminescentes e dispositivos eletrônicos pessoais distribuídos em varias regiões do corpo dos profissionais. Os resultados mostraram que, com apenas uma quimioembolização por semana, o médico principal pode ultrapassar o limite anual de 20 mSv para o cristalino quando não são utilizados dispositivos de radioproteção como óculos ou telas de acrílico plumbíferos. O valor mais alto de equivalente de dose pessoal Hp(d) por procedimento medido no corpo do médico principal foi 5135,3 μSv no pé esquerdo. A ausência da cortina plumbífera durante a realização dos procedimentos é uma explicação para os valores altos registrados. Os valores médios de dose efetiva por procedimento para o médico principal, médico auxiliar e anestesista numa das instituições acompanhadas foram: 13 μSv, 6,1 μSv e 13,7 μSv, respectivamente. Estes resultados mostram que os níveis de exposição recebidos pelo anestesista em procedimentos de quimioembolização podem ser superiores aos do médico principal. Os resultados da dosimetria ocupacional com dosimetros eletrônicos mostraram que estes dispositivos podem ser utilizados de forma complementar na estimativa da dose ocupacional no cristalino em procedimentos de quimioembolização hepática. Nas seis instituições avaliadas observou-se uma alta variabilidade nos valores de dose no paciente e equipe médica, devido, principalmente, ao desempenho dos equipamentos, complexidade dos procedimentos, características físicas dos pacientes e experiência dos médicos. / Among interventional procedures, hepatic chemoembolization has been recognized as a complex procedure where high radiation doses to patients and medical staff are delivered. In some cases the patient has to endure several sessions to treat the same lesion, which increases even more the probability of skin injuries or stochastic effects. In Brazil, chemoembolization is widely used; however few dosimetric studies have been done so far. This study presents dosimetric results for medical staff and patients based on 109 hepatic chemoembolization procedures conducted in six hemodynamic departments in Recife, Pernambuco. The procedures were performed using digital angiography equipments from different manufacturers, using different technologies. Patient dosimetry comprised the measurement of the maximum skin dose (MSD), air kerma-area product (PKA) and reference air kerma (Ka,r). The MSD was measured using radiochromic films of type Gafchromic XR RV3. To assess the risk of stochastic effects, organ absorbed doses were calculated by Monte Carlo simulations using female and male anthropometric phantoms of the FASH and MASH series. MSDs between 180 and 5650 mGy were found based on the radiochromic film measurements. 40% of the patients monitored with radiochromic films received MSDs above the 2 Gy threshold for transient skin erythema. The findings of this study showed that the Ka,r can be used for risk estimates of tissue reactions in patients undergoing chemoembolization procedures. The Monte Carlo simulations showed that patients may receive organ doses between 500 mGy and 1 Gy. Occupational dosimetry was performed using thermoluminescent dosimeters and personal electronic devices distributed over various regions of the physician’s body. The results showed that the main operator could reach the annual limit of 20 mSv for the equivalent dose in the lens of the eyes with just one procedure per week if the radiation shields such as the ceiling suspended screen and goggles are not used. The highest values of personal dose equivalent Hp(d), measured in the body of the main operator was 5135.3 μSv in the left foot. Lack of table curtains explains the registered high values. Mean effective doses for the main operator, the auxiliary physician and the anesthesiologist in one of the institutions were 13 μSv, 6.1 μSv e 13.7 μSv, respectively. These results show that occupational doses received by the anesthesiologist in chemoembolization procedures may be higher than those received by the main operator. The results of the occupational dosimetry using electronic dosimeters showed that these devices can be used in a complementary way to estimate the occupational eye lens doses in hepatic chemoembolization procedures. High variability of radiation doses to patients and medical staff was observed among the six medical institutions, mainly because of the performance of X-ray equipments, complexity of the procedures, physical characteristics of the patients and the physician´s experience

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 radiology. / Tiivistelmä 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.