Exposição de profissionais de saúde a radiações ionizantes : confiança dos profissionais nas leituras de dosimetria individual

Resumo - O avanço tecnológico e científico no campo da Medicina tem favorecido a aplicação das radiações ionizantes nas áreas da Medicina Nuclear, Radiologia, Radioterapia e noutras especialidades relacionadas com a medicina de intervenção, como a Cardiologia. As Organizações de Saúde, com profissionais com risco de exposição a radiações ionizantes, são responsáveis, legislativamente, por assegurar a sua vigilância. Certificando a observação controlada das doses de exposição, os profissionais são monitorizados com dosímetros individuais e submetidos a vigilância médica. As leituras de dosímetria individual destes profissionais, originam por vezes, nos próprios, desconfianças e incertezas quanto aos valores medidos. Objectivo: avaliar o grau de confiança dos profissionais de saúde, expostos a radiações ionizantes, no sistema de monitorização individual. Metodologia: estudo observacional do tipo analítico- transversal, por questionário. Amostra de 190 Técnicos de Diagnóstico e Terapêutica de Cardiopneumologia, Medicina Nuclear, Radiologia, Radioterapia, expostos a radiações ionizantes, que exercem a sua actividade profissional em hospitais do concelho de Lisboa. Resultados: 51,1% dos Técnicos de Diagnóstico e Terapêutica não confiam nas leituras dos dosímetros, não se determinou uma relação estatisticamente significativa entre essa confiança, o tipo de dosímetro e a empresa que realiza as leituras. A confiança é maior nos que exercem em Organizações de Saúde públicas. 40,2% das Organizações de Saúde apresentam plano de vigilância médica, constatando-se uma falta de conformidade entre os Técnicos de Diagnóstico e Terapêutica, nalguns hospitais, relativamente à existência desse plano no respectivo hospital. A margem de erro associado ao estudo é de 5,09%, com um nível de confiança de 95%. -----------Abstract - The technological and scientific advances in the field of medicine has encouraged the application of ionizing radiation with a considerable positive contribution in the areas of Nuclear Medicine, Radiology, Radiotherapy and other specialties related to medical intervention like Cardiology. The Health Organizations that arise the risk of occupational exposure to ionizing radiation and is their responsibility to ensure monitoring, according the law. To ensure the monitoring of controlled doses of exposure, the exposed works use an individual dosimeter and undergo medical supervision. The individual dosimetry readings of health-care professionals, is sometimes questionable for themselves, arising distrust and uncertainty about the values measured. Objective: evaluate the degree of confidence of health professionals, exposed to radiation, on the system of individual monitoring. Methods: Observational study of cross-type analysis by questionnaire. Sample of 190 of technologists of Cardiopneumology, Nuclear Medicine, Radiology, Radiotherapy, exposed to ionizing radiation, which work in hospitals on the region of Lisbon. Results: 51.1% of technologists does not rely on the readings of their dosimeters, and wasn’t determined a statistically significant relationship between this trust, the type of dosimeter and the company that makes the readings(s) of their(s) dosimeter(s). The confidence in the readings is higher in public Health Organizations. 40.2% of the Health Organizations have medical monitoring plan and there is a disagreement between technologists, in some hospitals, relatively to the existence of this plan in their hospital. It was estimated that the u

Sondagem de Belverde (Cenozóico, Península de Setúbal, Portugal). Diagrafias

In the aim of the project "Recognition of the Miocene of the distal region of the Lower Tagus Basin through a borehole with continuous sampling", Temperature, Natural Gamma Ray, Neutron (almost in all the borehole), Sonic, SP and SPR (in two small sections in upper and lower parts of the Miocene Series) geophysical logs were carried on. Interpretation of those logs and comparison with chronological, lithostratigraphical, micropaleontological and clay mineraIs data; helped in the definition of depositional sequences and to obtain paleoenvironmental reconstructions that could lead to a better understanding of the evolution of the Setúbal Península and Lisboa regions Miocene gulf. Log data agree with the lithologic succession observed in the Belverde borehole, essentially silty sandstones/sandy siltstones (with variable clay content) to clays, often with marly intercalations. Sonic logs (and Neutron logs, in general) reflect the sediments porosity. The higher acoustic velocities are often related to compact/massive layers as claystones and/or limestones and rather fossiliferous marly layers. Lower values are obtained for porous, silty sandstones (fossiliferous and with scarce clay content) and bio-calcareous sandstones. As indicative, we obtained the mean values of 2500-3000m/s for the higher velocities and 1300-1600m/s for the lowest ones. ln Natural Gamma Ray log, the radiation peaks can be correlated to often fossiliferous marly micaceous layers. Radioactive micas are present. It seems that the gamma peaks and the depositional sequences previously defined for the Lower Tagus Basin (see Antunes et al., 1999, 2000; Pais et al., 2002) can be correlated, taking also into account the whole available micropaleontological, palynological and isotopic evidence.

Medição dos níveis de referência de diagnóstico em tomografia computorizada para exames do abdómen

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Biomédica

Medição dos níveis de referência de diagnóstico em tomografia computorizada para exames de cabeça e pescoço

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Biomédica

Protecção radiológica do doente em tomografia computorizada

RESUMO - A preocupação com os conhecimentos, atitudes, crenças e práticas, no que concerne à utilização de radiações ionizantes para fins de diagnóstico, e a sensibilização de todos os agentes envolvidos, médicos, técnicos, físicos, utentes e responsáveis pela Saúde Publica, relativamente aos níveis de radiação emitida nos exames de Tomografia Computorizada (TC), assume particular importância no domínio da Saúde Pública, na medida em que é necessário influenciar o desenvolvimento de práticas que promovam, auditem e garantam a prestação do controlo da qualidade radiológica e dosimétrica nos serviços de Radiologia a nível Nacional. Para tal, e no âmbito da publicação de estudos já realizados ao nível da União Europeia, ―Orientações Europeias dos Critérios de Qualidade para a Tomografia Computorizada (1999) ‖, é proposto estabelecer orientações na realização de estudos que permitam, numa primeira fase, estabelecer a comparação com os resultados obtidos pelos mecanismos de Controlo da Qualidade (CQ), analisar e proceder aos ajustes (se necessário) e, numa segunda fase, implementar uma moldura sistemática de avaliação periódica dos níveis de dose de radiação por exame TC e que permita a monitorização dos dados. Nesse sentido, propõe-se a realização de um Estudo Nacional que envolva a rede hospitalar pública, privada e universitária, partindo da metodologia utilizada em estudos prévios noutros países da Europa, como seja, selecção do equipamento de TC existente na Instituição Hospitalar, onde serão reunidas informações através do preenchimento de questionários relativos ao equipamento a utilizar. Serão recolhidos dados relativos ao utente, ao equipamento e parâmetros de aquisição de imagem, que permitam identificar os níveis de referência de diagnóstico (NRD) em TC, na realidade Portuguesa. Foi efectuado um estudo piloto numa instituição EPE e os valores obtidos não são significativos, nem podem assumir valor preditivo dado o reduzido tamanho da amostra. Apesar disso, sugerem a existência de parâmetros que podem ser alterados e com isso podem fazer variar a dose de radiação utilizada. ENSP/UNL Maria de Fátima Vaz de Carvalho 5 Espera-se obter com este estudo, como foi referido, a base do estabelecimento dos NRD em TC em Portugal. ----------------- ABSTRACT - The purpose of this study, in an empirical point of view, emerges from concern with the knowledge, attitudes, beliefs and practices regarding the use of ionizing radiation for diagnostic purposes and awareness of all actors involved, medical physical, technical, and responsible public health for the development of practices that promote, audited and ensure the provision of radiological quality control and dosing in radiology service at national level. In view of the complexity and characteristics involved in relation to ionizing radiation, all assume their part in protecting the physical integrity of each user and a global perspective, to ensure the safeguarding of public health, while global and globalizing factor. To this end, and in the context of the publication of studies already carried out at European Union level, "European guidelines for quality criteria for computed tomography", it is proposed to establish guidelines in conducting studies to initially establish the comparison with the results obtained by QC and make adjustments if necessary, and subsequently implement a systematic periodic assessment frame that allows monitoring of data. Accordingly, it is proposed to conduct a national study involving the public network, private and University hospitals, that extends from the methodology used in previous studies in other countries of Europe, as is, selection of equipment of existing CT in Hospital Institution, where information will be gathered by filling out questionnaires concerning the equipment to be used. Data will be collected for the wearer, equipment and parameters of image acquisition, identifying diagnostic reference levels (NRD) in CT in Portuguese fact. A pilot study was carried out in an institution EPE and the values obtained are not significant, nor can they take predictive value given the small sample size. Despite this, suggest the existence of parameters that can be changed and this can vary the dose of radiation used It is hoped to get with this study, as mentioned, the basis of the establishment of NRD in CT in Portugal.

Monte Carlo simulations for dosimetric verification in photon and electron beam radiotherapy

Dissertação para obtenção do Grau de Doutor em Engenharia Biomédica

Study of nuclear reactions relevant for astrophysics by Micro-AMS

Dissertação para obtenção do Grau de Doutor em Física

Retrospective evaluation of bone pain palliation after samarium-153-EDTMP therapy

PURPOSE: The aim of this study was to evaluate the degree of metastatic bone pain palliation and medullar toxicity associated with samarium-153-EDTMP treatment. METHODS: Seventy-three patients with metastatic bone pain having previously undergone therapy with samarium-153-EDTMP (1 mCi/kg) were retrospectively evaluated. Routine follow-up included pain evaluation and blood counts for 2 months after treatment. Pain was evaluated using a subjective scale (from 0 to 10) before and for 8 weeks after the treatment. Blood counts were obtained before treatment and once a week for 2 months during follow-up. Dosimetry, based upon the urinary excretion of the isotope, was estimated in 41 individuals, and the resulting radiation absorbed doses were correlated with hematological data. RESULTS: Reduction in pain scores of 75% to 100% was obtained in 36 patients (49%), with a decrease of 50% to 75%, 25% to 50%, and 0% to 25% in, respectively, 20 (27%), 10 (14%), and 7 (10%) patients. There was no significant relationship between the pain response and location of the primary tumor (breast or prostate cancer). Mild to moderate myelosuppression was noted in 75.3% of patients, usually with hematological recovery at 8 weeks. The mean bone marrow dose was 347 ± 65 cGy, and only a weak correlation was found between absorbed dose and myelosuppression (Pearson coefficient = .4). CONCLUSIONS: Samarium-153-EDTMP is a valuable method for metastatic bone pain palliation. A mild to moderate and transitory myelosuppression is the main toxicity observed after samarium therapy, showing a weak correlation with dosimetric measures.

Singularities of the dynamical structure factors of the spin-1/2 XXX chain at finite magnetic field

We study the longitudinal and transverse spin dynamical structure factors of the spin-1/2 XXX chain at finite magnetic field h, focusing in particular on the singularities at excitation energies in the vicinity of the lower thresholds. While the static properties of the model can be studied within a Fermi-liquid like description in terms of pseudoparticles, our derivation of the dynamical properties relies on the introduction of a form of the ‘pseudofermion dynamical theory’ (PDT) of the 1D Hubbard model suitably modified for the spin-only XXX chain and other models with two pseudoparticle Fermi points. Specifically, we derive the exact momentum and spin-density dependences of the exponents ζτ(k) controlling the singularities for both the longitudinal  and transverse (τ = t) dynamical structure factors for the whole momentum range  , in the thermodynamic limit. This requires the numerical solution of the integral equations that define the phase shifts in these exponents expressions. We discuss the relation to neutron scattering and suggest new experiments on spin-chain compounds using a carefully oriented crystal to test our predictions.

A systematic study of the structural and magnetic properties of Mn-, Co-, and Ni-Doped Colloidal Fe3O4 nanoparticles

A series of colloidal MxFe3-xO4 (M = Mn, Co, Ni; x = 0–1) nanoparticles with diameters ranging from 6.8 to 11.6 nm was synthesized by hydrothermal reaction in aqueous medium at low temperature (200 °C). Energy-dispersive X-ray microa-nalysis and inductively coupled plasma spectrometry confirms that the actual elemental compositions agree well with the nominal ones. The structural properties of obtained nanoparticles were investigated by using powder X-ray diffraction, Raman scattering, Mössbauer spectroscopy, and electron microscopy. The results demonstrate that our synthesis technique leads to the formation of chemically uniform single-phase solid solution nanoparticles with cubic spinel structure, confirming the intrinsic doping. Magnetic studies showed that, in comparison to Fe3O4, the saturation magnetization of MxFe3-xO4 (M = Mn, Ni) decreases with increasing dopant concentration, while Co-doped samples showed similar saturation magnetizations. On other hand, whereas Mn- and Ni-doped nanoparticles exhibits superparamagnetic behavior at room temperature, ferromagnetism emerges for CoxFe3-xO4 nanoparticles, which can be tuned by the level of Co doping.

Nonlinear behavior of gelatin networks reveals a hierarchical structure

We investigate the strain hardening behavior of various gelatin networks-namely physical gelatin gel, chemically cross-linked gelatin gel, and a hybrid gel made of a combination of the former two-under large shear deformations using the pre-stress, strain ramp, and large amplitude oscillations shear protocols. Further, the internal structures of physical gelatin gels and chemically cross-linked gelatin gels were characterized by small angle neutron scattering (SANS) to enable their internal structures to be correlated with their nonlinear rheology. The Kratky plots of SANS data demonstrate the presence of small cross-linked aggregates within the chemically cross-linked network whereas, in the physical gelatin gels, a relatively homogeneous structure is observed. Through model fitting to the scattering data, we were able to obtain structural parameters, such as the correlation length (ξ), the cross-sectional polymer chain radius (Rc) and the fractal dimension (df) of the gel networks. The fractal dimension df obtained from the SANS data of the physical and chemically cross-linked gels is 1.31 and 1.53, respectively. These values are in excellent agreement with the ones obtained from a generalized nonlinear elastic theory that has been used to fit the stress-strain curves. The chemical cross-linking that generates coils and aggregates hinders the free stretching of the triple helix bundles in the physical gels.

О возможности изучения солнечно -суточной вариаций с помощью нейтронного супермонитора космофизических обсерватории им. В. Койава

ვ. ქოიავას სახელობის კოსმოფიზიკური და ქ. დუშეთის მაგნიტური ობსერვატორიების გაერთიანებული ერთობლივი სინქრონული მუშაობის შედეგად განხილულია მზე-დღეღამური ვარიაციების ზუსტი გაზომვების ჩატარება ორიგინალური მეთოდის გამოყენებით.

reale Strahlenbild bei einer Röntgenthoraxaufnahme

Digital radiography, thoracic imaging, micro-dosimetry, high-resolution x-ray film, drum scanner, x-ray intensity pattern, analysis of frequency components

Determinació de la ubicació estructural dels ions Yb3+ i Nb3+ en Yb:RTP, Nb:RTP i (Nb,Yb):RTP

Estudi elaborat a partir d’una estada al Stony Brook University al juliol del 2006. El RbTiOPO4 (RTP) monocristal•lí és un material d' òptica no lineal molt rellevant i utilitzat en la tecnologia làser actual, químicament molt estable i amb unes propietats físiques molt destacades, entre elles destaquen els alts coeficients electro-òptics i l'alt llindar de dany òptic que presenta. En els últims anys s’està utilitzant tecnològicament en aplicacions d'òptica no lineal en general i electro-òptiques en particular. En alguns casos ja ha substituït, millorant prestacions, a materials tals com el KTP o el LNB(1). Dopant RTP amb ions lantànids (Ln3+) (2-4), el material es converteix en un material làser auto-doblador de freqüència, combinant les seves propietats no lineals amb les de matriu làser. El RTP genera radiació de segon harmònic (SHG) a partir d’un feix fonamental amb longituds d’ona inferiors a 990 nm, que és el límit que presenta el KTP.La determinació de la ubicació estructural i l’estudi de l'entorn local del ions actius làser és de fonamental importància per a la correcta interpretació de les propietats espectroscòpiques d’aquest material. Mesures de difracció de neutrons sobre mostra de pols cristal•lí mostren que els ions Nb5+ i Ln3+ només substitueixin posicions de Ti4+ (8-9). Estudis molt recents d'EPR (electron paramagnetic resonance) semblen indicar que quan la concentració d'ió Ln3+ es baixa, aquest ió presenta la tendència a substituir l'ió alcalí present a l'estructura (10).Després dels resultats obtinguts en el present treball a partir de la tècnica EXAFS a la instal•lació sincrotò del Brookhaven National Laboratory/State University of New York (Stony Brook) es pot concloure definitivament que els ions Nb s’ubiquen en la posició Ti (1) i que els ions Yb3+ es distribueixen paritariament en les dues posicions del Ti (1 i 2). Aquests resultats aporten una valuosa informació per a la correcta interpretació dels espectres, tant d’absorció com d’emissió, del material i per la avaluació dels paràmetres del seu comportament durant l'acció làser.

A peripheral dose calculation model for estimating second cancer risk after breast radiotherapy

AbstractBreast cancer is one of the most common cancers affecting one in eight women during their lives. Survival rates have increased steadily thanks to early diagnosis with mammography screening and more efficient treatment strategies. Post-operative radiation therapy is a standard of care in the management of breast cancer and has been shown to reduce efficiently both local recurrence rate and breast cancer mortality. Radiation therapy is however associated with some late effects for long-term survivors. Radiation-induced secondary cancer is a relatively rare but severe late effect of radiation therapy. Currently, radiotherapy plans are essentially optimized to maximize tumor control and minimize late deterministic effects (tissue reactions) that are mainly associated with high doses (» 1 Gy). With improved cure rates and new radiation therapy technologies, it is also important to evaluate and minimize secondary cancer risks for different treatment techniques. This is a particularly challenging task due to the large uncertainties in the dose-response relationship.In contrast with late deterministic effects, secondary cancers may be associated with much lower doses and therefore out-of-field doses (also called peripheral doses) that are typically inferior to 1 Gy need to be determined accurately. Out-of-field doses result from patient scatter and head scatter from the treatment unit. These doses are particularly challenging to compute and we characterized it by Monte Carlo (MC) calculation. A detailed MC model of the Siemens Primus linear accelerator has been thoroughly validated with measurements. We investigated the accuracy of such a model for retrospective dosimetry in epidemiological studies on secondary cancers. Considering that patients in such large studies could be treated on a variety of machines, we assessed the uncertainty in reconstructed peripheral dose due to the variability of peripheral dose among various linac geometries. For large open fields (> 10x10 cm2), the uncertainty would be less than 50%, but for small fields and wedged fields the uncertainty in reconstructed dose could rise up to a factor of 10. It was concluded that such a model could be used for conventional treatments using large open fields only.The MC model of the Siemens Primus linac was then used to compare out-of-field doses for different treatment techniques in a female whole-body CT-based phantom. Current techniques such as conformai wedged-based radiotherapy and hybrid IMRT were investigated and compared to older two-dimensional radiotherapy techniques. MC doses were also compared to those of a commercial Treatment Planning System (TPS). While the TPS is routinely used to determine the dose to the contralateral breast and the ipsilateral lung which are mostly out of the treatment fields, we have shown that these doses may be highly inaccurate depending on the treatment technique investigated. MC shows that hybrid IMRT is dosimetrically similar to three-dimensional wedge-based radiotherapy within the field, but offers substantially reduced doses to out-of-field healthy organs.Finally, many different approaches to risk estimations extracted from the literature were applied to the calculated MC dose distribution. Absolute risks varied substantially as did the ratio of risk between two treatment techniques, reflecting the large uncertainties involved with current risk models. Despite all these uncertainties, the hybrid IMRT investigated resulted in systematically lower cancer risks than any of the other treatment techniques. More epidemiological studies with accurate dosimetry are required in the future to construct robust risk models. In the meantime, any treatment strategy that reduces out-of-field doses to healthy organs should be investigated. Electron radiotherapy might offer interesting possibilities with this regard.RésuméLe cancer du sein affecte une femme sur huit au cours de sa vie. Grâce au dépistage précoce et à des thérapies de plus en plus efficaces, le taux de guérison a augmenté au cours du temps. La radiothérapie postopératoire joue un rôle important dans le traitement du cancer du sein en réduisant le taux de récidive et la mortalité. Malheureusement, la radiothérapie peut aussi induire des toxicités tardives chez les patients guéris. En particulier, les cancers secondaires radio-induits sont une complication rare mais sévère de la radiothérapie. En routine clinique, les plans de radiothérapie sont essentiellement optimisées pour un contrôle local le plus élevé possible tout en minimisant les réactions tissulaires tardives qui sont essentiellement associées avec des hautes doses (» 1 Gy). Toutefois, avec l'introduction de différentes nouvelles techniques et avec l'augmentation des taux de survie, il devient impératif d'évaluer et de minimiser les risques de cancer secondaire pour différentes techniques de traitement. Une telle évaluation du risque est une tâche ardue étant donné les nombreuses incertitudes liées à la relation dose-risque.Contrairement aux effets tissulaires, les cancers secondaires peuvent aussi être induits par des basses doses dans des organes qui se trouvent hors des champs d'irradiation. Ces organes reçoivent des doses périphériques typiquement inférieures à 1 Gy qui résultent du diffusé du patient et du diffusé de l'accélérateur. Ces doses sont difficiles à calculer précisément, mais les algorithmes Monte Carlo (MC) permettent de les estimer avec une bonne précision. Un modèle MC détaillé de l'accélérateur Primus de Siemens a été élaboré et validé avec des mesures. La précision de ce modèle a également été déterminée pour la reconstruction de dose en épidémiologie. Si on considère que les patients inclus dans de larges cohortes sont traités sur une variété de machines, l'incertitude dans la reconstruction de dose périphérique a été étudiée en fonction de la variabilité de la dose périphérique pour différents types d'accélérateurs. Pour de grands champs (> 10x10 cm ), l'incertitude est inférieure à 50%, mais pour de petits champs et des champs filtrés, l'incertitude de la dose peut monter jusqu'à un facteur 10. En conclusion, un tel modèle ne peut être utilisé que pour les traitements conventionnels utilisant des grands champs.Le modèle MC de l'accélérateur Primus a été utilisé ensuite pour déterminer la dose périphérique pour différentes techniques dans un fantôme corps entier basé sur des coupes CT d'une patiente. Les techniques actuelles utilisant des champs filtrés ou encore l'IMRT hybride ont été étudiées et comparées par rapport aux techniques plus anciennes. Les doses calculées par MC ont été comparées à celles obtenues d'un logiciel de planification commercial (TPS). Alors que le TPS est utilisé en routine pour déterminer la dose au sein contralatéral et au poumon ipsilatéral qui sont principalement hors des faisceaux, nous avons montré que ces doses peuvent être plus ou moins précises selon la technTque étudiée. Les calculs MC montrent que la technique IMRT est dosimétriquement équivalente à celle basée sur des champs filtrés à l'intérieur des champs de traitement, mais offre une réduction importante de la dose aux organes périphériques.Finalement différents modèles de risque ont été étudiés sur la base des distributions de dose calculées par MC. Les risques absolus et le rapport des risques entre deux techniques de traitement varient grandement, ce qui reflète les grandes incertitudes liées aux différents modèles de risque. Malgré ces incertitudes, on a pu montrer que la technique IMRT offrait une réduction du risque systématique par rapport aux autres techniques. En attendant des données épidémiologiques supplémentaires sur la relation dose-risque, toute technique offrant une réduction des doses périphériques aux organes sains mérite d'être étudiée. La radiothérapie avec des électrons offre à ce titre des possibilités intéressantes.