Um programa de monitoramento para fins de proteção radiológica deve mostrar como ele auxilia na obtenção e demonstração de um grau de proteção adequado e comprovar que as condições de trabalho continuam satisfatórias com o transcorrer do tempo. Para o controle operacional das exposições à radiação ionizante em qualquer local de trabalho, a Comissão Internacional de Proteção Radiológica (CIPR) recomenda um programa de proteção radiológica operacional, proporcional ao grau de risco, para garantir o gerenciamento efetivo das medidas necessárias para se satisfazer o principio da otimização. O presente trabalho de pesquisa tem como premissa o potencial das Tecnologias da Informação e Comunicação (TIC) como ferramenta para a comunicação e disseminação do conhecimento em Proteção Radiológica. O trabalho inclui a informatização da filosofia e técnica do monitoramento e sua otimização, unificando e inter-relacionando informações advindas de diversas publicações nacionais e internacionais, oferecendo às instalações radiativas brasileiras um veículo completo para informação e pesquisa, que permite dimensionar os esforços de otimização tornando-os eficazes e justificados. O sistema oferece ainda tópicos de discussões no intuito de ampliar o repertório dos profissionais do campo da proteção radiológica, suscitando novas reflexões a favor da segurança. Trata-se dos temas desenvolvidos nesta tese, a saber: a necessidade de um monitoramento auditor e discussões mais aprofundadas sobre as exposições potenciais. As reflexões propostas na presente tese vêm ao encontro das novas exigências internacionais, propondo ações passíveis de serem incorporadas na prática laboral. Dentro dos princípios da proteção radiológica, a implementação de um programa de monitoramento auditor permite avaliar se os critérios e ações previamente estabelecidas pelo Serviço de Proteção Radiológica são ou não atendidos, se foram implementados com eficácia e se permanecem adequados. Os fatos resultantes dos procedimentos de auditoria auxiliam a detectar deficiências no processo, possibilitando conclusões e recomendações diante de possíveis fatores desencadeadores de exposições indevidas. Por meio de exames sistemáticos das atividades realizadas em cada tipo de monitoramento, a auditoria infere segurança ao processo, respaldando o trabalhador na realização do monitoramento relacionado com a tarefa e respaldando a instalação, que empreende ações responsáveis a favor da segurança. Em relação às exposições potenciais, somente duas publicações da CIPR são expressivas e desenvolvem o assunto. Entretanto, ainda que forneçam a fundamentação teórica, são incompletas em seus exemplos. Há uma grande falta de conhecimento das probabilidades de falhas, o que atualmente constitui um vasto campo de pesquisa da proteção radiológica. A presente tese propõe, a partir de árvores de falhas, caminhos que auxiliam a quantificar probabilisticamente a ocorrência das exposições potenciais e a probabilidade de se atingir um determinado valor da dose. Acreditamos que o potencial das TIC contribuirá largamente para a disseminação da informação para as instalações radiativas, estimulando o desenvolvimento neste país de grandes extensões territoriais, onde permanece um desafio oferecer o acesso à informação ao maior número de pessoas possível, minimizando custos e maximizando resultados. / A monitoring program for the purposes of radiological protection should demonstrate an adequate protection degree and prove that working conditions remain appropriate as time goes by. For operational control of exposures to ionizing radiation in any workplace, the International Comission on Radiation Protection (ICRP) recommends establishing a program of operational radiation protection, proportional to the risk, to ensure the effective management of all necessary measures to satisfy the principle of optimization. This research work focus on the potential value of Information and Communication Technologies (ICTs) to enhance communication and education on Radiological Protection throughout Brazil. The work includes the informatization of the monitoring policy and techniques, interrelating information currently scattered in several documents, providing Brazilian radioactive facilities a complete repository for research, consultation and information, which allows to size optimization efforts by technology, enabling them to be effective and justified. The content of monitoring programs involves not only the collection and interrelationship of existing information in the publications, but also new approaches from some recommendations, presenting some initiatives towards safety. In this sense, the two contents researched and expanded are: the need for an auditor monitoring and discussions on potential exposures. The recommendations proposed in this thesis meet the new international requirements stablished by the International Agency of Nuclear Energy (IAEA) and propose appropriate actions to be incorporated into labor practice. Respecting the scope of the principles of radiological protection, an auditing program permits to evaluate whether criteria and actions previously established by Radiological Protection Service are effectively implemented and remain appropriate as time goes by. The results of auditing procedures help to detect deficiencies in the process, enabling conclusions and recommendations, avoiding possible triggers of undue exposures. Through systematic examinations of activities in each type of monitoring, auditing attempt to ensure the process, supporting the employee in performing task-related monitoring and support the facility that choose responsible actions towards safety. Furthermore, regarding potential exposures, only two publications of ICRP develop expressively the issue. Even though these publications provide the fundamental theory, they are incomplete in their examples. There is still lack of knowledge of failure probabilities, which currently constitutes a broad research field in radiological protection. This research work proposes the development of fault trees, suggesting paths to quantify probabilistically the occurrence of potential exposures, as well as probabilities to reach a certain level of dose. We believe that the potential of ICT shall contribute greatly to provide information where it is needed, stimulating development in this large country where it is a strong challenge to ensure access to information to as many people as possible, minimizing costs and optimizing results.

O uso e a aplicação cada vez mais constante da tecnologia nuclear consistente em áreas relacionadas à saúde, energia, industrial, bélica, agrícola, entre outras, faz com que haja a necessidade de uma regulamentação de acordo com os padrões de segurança e proteção radiológica internacionais. Dessa forma, utilizando-se de conceitos provenientes do Direito Constitucional, do Direito Ambiental e do Direito do Trabalho, o enfoque da presente pesquisa foi investigar a difícil questão da competência nuclear e a competência ambiental, a impossibilidade de legislar dos Estados, bem como a falta de regulamentação sobre Rejeitos radioativos. Para tanto, foram atualizados e revisados critérios e métodos de interpretação constitucional para solucionar possíveis antinomias jurídicas advindas de múltipla positivação de normas pelos entes federados que dificultam tanto o asseguramento quanto o aprimoramento da Proteção radiológica do trabalhador e do meio ambiente. Finalmente, a hipótese considerada demonstrou que as mudanças na estrutura legislativa nas três esferas de poderes são necessárias, visando à aplicabilidade de responsabilidade legal na esfera nuclear, principalmente no que se refere às entidades administrativas e estatais. / The use and increasingly steady application of consistent nuclear technology in areas related to health, energy, industrial, war, agriculture, among others, means that there is a need for regulation in accordance with the safety standards and international radiological protection . Thus, using concepts from the Constitutional Law, Environmental Law and Labor Law, the focus of this research was to investigate the difficult issue of nuclear competence and environmental responsibility, the impossibility of legislating states, as well as the lack of regulation on radioactive waste. Therefore, it has been updated and revised criteria and methods of constitutional interpretation to solve possible legal antinomies arising from multiple positivation of the federal entities rules that hinder both the assurance and the improvement of radiation protection of workers and the environment. Finally, the working hypothesis has shown that changes in the legislative framework in the three spheres of power is needed in order to applicability of legal liability in the nuclear sphere, especially with regard to administrative and state entities

O uso e a aplicação cada vez mais constante da tecnologia nuclear consistente em áreas relacionadas à saúde, energia, industrial, bélica, agrícola, entre outras, faz com que haja a necessidade de uma regulamentação de acordo com os padrões de segurança e proteção radiológica internacionais. Dessa forma, utilizando-se de conceitos provenientes do Direito Constitucional, do Direito Ambiental e do Direito do Trabalho, o enfoque da presente pesquisa foi investigar a difícil questão da competência nuclear e a competência ambiental, a impossibilidade de legislar dos Estados, bem como a falta de regulamentação sobre Rejeitos radioativos. Para tanto, foram atualizados e revisados critérios e métodos de interpretação constitucional para solucionar possíveis antinomias jurídicas advindas de múltipla positivação de normas pelos entes federados que dificultam tanto o asseguramento quanto o aprimoramento da Proteção radiológica do trabalhador e do meio ambiente. Finalmente, a hipótese considerada demonstrou que as mudanças na estrutura legislativa nas três esferas de poderes são necessárias, visando à aplicabilidade de responsabilidade legal na esfera nuclear, principalmente no que se refere às entidades administrativas e estatais. / The use and increasingly steady application of consistent nuclear technology in areas related to health, energy, industrial, war, agriculture, among others, means that there is a need for regulation in accordance with the safety standards and international radiological protection . Thus, using concepts from the Constitutional Law, Environmental Law and Labor Law, the focus of this research was to investigate the difficult issue of nuclear competence and environmental responsibility, the impossibility of legislating states, as well as the lack of regulation on radioactive waste. Therefore, it has been updated and revised criteria and methods of constitutional interpretation to solve possible legal antinomies arising from multiple positivation of the federal entities rules that hinder both the assurance and the improvement of radiation protection of workers and the environment. Finally, the working hypothesis has shown that changes in the legislative framework in the three spheres of power is needed in order to applicability of legal liability in the nuclear sphere, especially with regard to administrative and state entities

Thesis (MPH. ) --University of Limpopo, 2014 / This dissertation reports on findings from a qualitative research that sought to investigate adherence and compliance to radiation safety protocols by radiographers and dental professionals in the Waterberg District. The study also sought to determine the knowledge the participants had on the chronic ill-effects of occupational exposure to radiation, safety protocols and their professional experience in dealing with occupational exposure to radiation. Altogether 60 participants from 8 health institutions in the Waterberg district took part in the study. They were compromised of males and females with ages ranging from 22-60 years. The response rate was 75% (n=45/60). The empirical data of the study shows a consistent yet disconcerting pattern among practitioners about safety compliance, safety protocols and their understanding of long term effect of occupational exposure to radiation. Despite their impressive knowledge of X-rays being a source of ionizing radiation, the level of their understanding of ill-effects thereof was of great concern. The general failure by both professionals in complying with the most basic safety protocols is worrisome. In a nutshell, yet some of the practitioners were found to be greatly exposed to radiation, their daily practices were found not consistent with procedures dictated by the guidelines on the use of medical X-ray equipment. Overall, only 59% of radiographers always wore their dosimeters, a basic monitoring and protective tool to measure their radiation exposure. In the study, only 38% of the dentists were found to be compliant and overwhelmingly alluded this to their employers being unable to supply them with crucial protective clothing, a finding that the researcher cannot dispute as indicated in the responses by the two groups. The failure of the employer in enforcing monitoring and assuring safety to the employees, patients and the general public emerged from this study. Various non-compliance patterns could be attributed to the participants and others to the employer. Protocols as clearly stipulated in R1332 of Hazardous Substance Act 15 of 1973 and other guidelines are not adhered to.

<p>Silicon diodes compared to other types of dosimeters have several attractive properties, such as an excellent spatial resolution, a high sensitivity, and clinically practical to use. These properties make silicon diodes a preferred dosimeter for relative dosimetry for several types of measurements in small field dosimetry, e.g., stereotactic treatments and intensity modulated radiotherapy (IMRT). Silicon diodes are, however, limited by an energy dependent response variation in photon beams, resulting in that the diode readout per dose to the phantom medium varies with photon spectral changes, thereby introducing a significant uncertainty in the measured data. The traditional solution for the energy dependent over-response caused by low-energy photons is to use diodes with a shielding filter of high atomic number. These shielded diodes, however, show an incorrect readout for small fields due to electrons scattered from the shielding (Griessbach <em>et al</em>. 2005). In regions with degraded lateral electron equilibrium (LEE) shielded diodes over-respond due to an increased degree of LEE, as a consequence of the high density shielding (Lee <em>et al</em>. 2002).</p><p>In this work a prototype software that corrects for the energy dependent response of a silicon diode is developed and validated for small field sizes. The developed software is based on the novel concept of Monte Carlo (MC) simulated fluence pencil beam kernels to calculate spectra (Eklund and Ahnesjö 2008), and the spectra based silicon diode response model proposed by Eklund and Ahnesjö (2009). The software was also extended to include correction of ionization chambers, for the energy dependent Spencer-Attix water/air stopping power ratio (<em>s</em>_w,air). The calculated <em>s</em>_w,air are shown to be in excellent agreement with published values to better than 0.1% for most values, the maximum deviation being 0.3%.</p><p>Measured relative depth doses, relative profiles, and output factors in water, for small square field sizes, for 6 MV and 15 MV clinical photon beams are presented in this work. The results show that the unshielded Scanditronix-Wellhöfer EFD^3G silicon diode response, corrected by the developed software, is in excellent agreement with reference ionization chamber measurements (corrected for change in <em>s</em>_w,air), the maximum deviation being 0.4%.</p><p>Measurements with two types of shielded diodes, namely Scanditronix-Wellhöfer PFD silicon diodes (FP1990 and FP2730), are also included in this work. The shielded diodes are shown to have an over-response as large as 2-3.5% for field sizes smaller than 5 cm x 5 cm. The presented results also suggest a difference in accuracy as large as 0.5-1% between the two types of shielded diodes, where the spectral composition at the measurement position dictates which type of diode is more accurate.</p><p>The fast correction of silicon diodes provided by the developed software is more accurate than shielded diodes for small field sizes, and can in radiotherapeutic clinical practice increase the dosimetric accuracy of silicon diodes.</p>

<p>A variety of radiation sources exist at the Department of Radiology and the Department of Nuclear Medicine at Karolinska University Hospital Huddinge. Radiation sources can also be found in areas outside of these departments due to the wide use of mobile xray machines and fluoroscopic c-arm equipment and also due to the movement of patients that have received diagnostic or therapeutic doses of radionuclides.</p><p>In a proposal for a new legislation from the Swedish Radiation Protection Authority (SSI), which was later issued as legislation SSI FS 2005:6, the effective doses of the general public from a practice using ionising radiation need to be kept below stated limit of 0.1 mSv/year. This project was performed to verify the dose limit for individuals of the general public in the above mentioned practices.</p><p>Long-term measurements with TL-dosimeters were utilised to carry out the environmental monitoring of the areas throughout the Departments of Radiology and Nuclear Medicine. To assess the contribution of ionising radiation from rooms housing mobile fluoroscopic c-arm equipment to surrounding areas, a tissue equivalent phantom of size (30×30×20 cm3) was employed to simulate a patient and the scattered radiation was monitored by using area monitors, such as portable proportional counters. The annual effective doses were calculated in terms of personal dose equivalent as well as ambient dose equivalent monitored using TL-dosimeters and area monitors, respectively. The stated limit of 0.1 mSv/year to the general public was verified by risk analysis.</p><p>An attempt to create a method for determining the amount of radiation shielding in terms of lead equivalence in walls, doors, protective glasses of manoeuvre rooms and cupboards of diagnostic x-ray labs was also performed using a radiation point source of 99mTc and a NaI scintillation detector. Depending on the accuracy in the measurements the amount of lead deviated slightly from the expected 2 mm value based on the former legislation SSI FS 1991:1.</p>

<p>Reference radiation fields for x-ray qualities are described by the International Organization of Standards (ISO). This study describes the procedure to establish nine different low energy X-ray qualities at the national metrology laboratory, Swedish Radiation Protection Authority, following the document ISO 4037. Measurements of tube voltage, half-value layer, mean energy and spectral resolution have been performed for qualities N-15, N-20, N-25, N-30, N-40, L-20, L-30, L-35 and L-55. Furthermore, dose equivalent conversion coefficients for operational quantities ambient dose equivalent, personal dose equivalent and directional dose equivalent have been calculated by folding the mono-energetic conversion factors with measured spectral distributions of the x-ray qualities. The spectral distributions were unfolded from pulse-height distributions to photon distributions using simulated data of the semi-conductor detector used for measurements, generated with the Monte Carlo code PENELOPE.</p>

<p>The tumor vasculature is poor and heterogeneous which may result in inadequate oxygenation and changed energy status. In addition the balance between cell proliferation and the rate of cell death is disturbed, which results in tumor growth. </p><p>The aims of this study were 1) to gain more insight into the relation between tumor vascularity, hypoxia, and proliferation in solid tumors, and 2) to study the changes and dynamics of tumor oxygenation in relation to the vascular architecture within individual tumors. For this purpose a double hypoxic marker method was developed, which was subsequently used to 3) determine the turnover rate of hypoxic cells in three different tumor models and 4) to study the effect of cytotoxic drugs on tumor hypoxia and cell death.</p><p>Solid tumor models grown in mice were used. The tumor microenvironment was investigated with exogenous cell markers for hypoxia (pimonidazole and CCI-103F), cell proliferation (BrdUrd) and blood perfusion (Hoechst 33342). The vasculature and the exogenous cell markers were visualized with immunohistochemical techniques. The tumor sections were scanned and quantified with an image analysis systemconsisting of a fluorescence microscope, CCD camera and image analysis software.</p><p>The spatial organization of hypoxia, proliferation, and tumor vasculature was analyzed in several xenograft lines. The study revealed two main hypoxic patterns that seemed to be the consequence of complex relations between vasculature, oxygen delivery, proliferation, and cell loss. The novel double hypoxic cell marker method, with sequential injection of two hypoxic markers, was developed to study dynamic changes of the tumor oxygenation. Based on varying injection intervals between the markers the hypoxic cell half-life was determined in three tumor lines, and ranged from 17 to 49 hours. Intra-tumoral changes in oxygenation status upon oxygen modifying treatments were measured with the double hypoxic marker method. Both decreased levels of tumor hypoxia after carbogen breathing (95%O2 and 5% CO2) and increased levels of tumor hypoxia, as a result of reduced tumor perfusion after hydralazine treatment was detected. Finally the double hypoxic marker assay was used to analyze the effects of the hypoxic cytotoxin tirapazamine in relation to the hypoxic cell population, which caused a reversible decrease of the hypoxic fraction.</p><p>The results presented in this thesis now form the basis for further studies to identify subpopulations of cells that represent specific targets for therapy, and to investigate the effects of different treatment modalities.</p>

<p> </p><p>Acquired data from dynamic contrast enhanced MRI measurements can be used to non-invasively assess tumour vascular characteristics through pharmacokinetic modelling. The modelling requires an arterial input function which is the concentration of contrast agent in the blood reaching the volume of interest as a function of time. The aim of this work is testing and optimizing a turboFLASH sequence to appraise its suitability for measuring the arterial input function by measuring phase.</p><p>Contrast concentration measurements in a phantom were done with both phase and relaxivity techniques. The results were compared to simulations of the experiment conditions to compare the conformance. The results using the phase technique were promising, and the method was carried on to in-vivo testing. The in-vivo data displayed a large signal loss which motivated a new phantom experiment to examine the cause of this signal reduction. Dynamic measurements were made in a phantom with pulsatile flow to mimic a blood vessel with a somewhat modified turboFLASH sequence. The conclusions drawn from analyzing the data were used to further improve the sequence and this modified turboFLASH sequence was tested in an in-vivo experiment. The obtained concentration curve showed significant improvement and was deemed to be a good representation of the true blood concentration.</p><p>The conclusion is that phase measurements can be recommended over relaxivity based measurements. This recommendation holds for using a slice selective saturation recovery turboFLASH sequence and measuring the arterial input function in the neck. Other areas of application need more thorough testing.</p><p> </p>

<p>The purpose of this work was to improve the diagnosis of intracranial hemorrhage with MRI, using, among others, T2*-w GE sequences. Various sequences were tested in rabbits at two magnetic field strengths. Then, the most effective technique was applied to stroke patients. </p><p>Experimental studies: The MR detectability of small experimental haematomas in the brain and of blood in the cerebrospinal fluid (CSF) spaces of 30 rabbits was evaluated. MRI examinations were performed at determined intervals. The last MR images were compared to formalin fixed brain sections and, in 16 rabbits, also to the histological findings. T2*-weighted GE sequences revealed all the intraparenchymal haematomas at 1.5 T, appearing strongly hypointense. Their signal patterns remained unchanged during the follow-up. Blood in the CSF spaces was best detected at 1.5T with T2*-weighted GE sequences during the first 2 days. FLAIR and SE sequences were rather insensitive.</p><p>Clinical studies: MR examinations were performed at 1.5T, including T1- and T2-w SE, FLAIR and T2*-w GE sequences. In the first clinical study, 66 intraparenchymal hematomas (IPH) of different sizes and ages were examined. T2*-w GE sequence was the most sensitive. On all the sequences, we found a big variety of signal patterns, without a clear relationship to the age of the hematomas. </p><p>In a second clinical study, MR examinations were performed to 83 patients with acute stroke: 43 presented acute IPH and 40 were used as controls. Old microhemorrhages (OMHs) were found in 60% of the patients with IPH, and in 15% of the controls. </p><p>Conclusion: T2*-weighted GE sequences are capable of revealing very small intraparenchymal hemorrhages at any stage, and blood in CSF spaces during at least the first 2 days. The age of IPHs cannot reliably be estimated with MRI. We have found a correlation between the presence of OMHs and acute intraparenchymal hematomas.</p>