Thesis (doctoral)--University of Göteborg, 1998. / Added t.p. with thesis statement inserted.

Submitted by Suelen Reis (suziy.ellen@gmail.com) on 2013-04-24T13:10:47Z No. of bitstreams: 1 DISSERTACAO - Marianna Torres.pdf: 3737774 bytes, checksum: dc2fecaa530f7b5bc4c0f507fbe6a184 (MD5) / Approved for entry into archive by Rodrigo Meirelles(rodrigomei@ufba.br) on 2013-05-08T11:48:36Z (GMT) No. of bitstreams: 1 DISSERTACAO - Marianna Torres.pdf: 3737774 bytes, checksum: dc2fecaa530f7b5bc4c0f507fbe6a184 (MD5) / Made available in DSpace on 2013-05-08T11:48:36Z (GMT). No. of bitstreams: 1 DISSERTACAO - Marianna Torres.pdf: 3737774 bytes, checksum: dc2fecaa530f7b5bc4c0f507fbe6a184 (MD5) Previous issue date: 2009 / A tomografia computadorizada de feixe cônico (TCFC) apresenta voxel reduzido, quando comparada à tomografia computadorizada convencional. Além disso, alguns aparelhos permitem a variação do tamanho do voxel para aquisição de imagens. Em geral, quanto menor o tamanho do voxel, melhor será a resolução. No entanto, para o aparelho i-CAT, por exemplo, um voxel menor está atrelado a um tempo de varredura mais longo, o que proporciona algumas desvantagens como maiores possibilidades de movimentação do paciente durante o exame e doses mais elevadas de radiação. Este trabalho tem como objetivo avaliar doses referenciais – produto dose-área (PDA) e dose de entrada na pele (DEP) – e acurácia de mensurações lineares feitas na mandíbula através de imagens de TCFC adquiridas com diferentes tamanhos de voxel, a fim de estabelecer o melhor protocolo a ser utilizado para realização de mensurações lineares. Oito mandíbulas secas foram submetidas a exames de TCFC, usando o aparelho i-CAT, a partir de quatro protocolos, a saber: p1) voxel de 0,2mm, 40seg e 46,72mAs; p2) voxel de 0,25mm, 40seg e 46,72mAs; p3) voxel de 0,3mm, 20seg e 23,87mAs; p4) voxel de 0,4mm, 20seg e 23,87mAs. A quilovoltagem permaneceu constante (120kVp). Para avaliação da acurácia das mensurações lineares, cortes tomográficos com visualização mais central dos marcadores, colocados em seis sítios em cada mandíbula, foram selecionados para realização de medidas verticais e horizontais, com o auxílio da ferramenta de mensuração de linha do Xoran (software do i-CAT). Os valores obtidos das mensurações diretas na mandíbula seca, com uso do paquímetro digital, após secção das mesmas nos sítios pré-estabelecidos, e das mensurações nas imagens tomográficas foram comparados e o erro de mensuração (EM) calculado. Para avaliação das doses referenciais, a medição do DEP foi realizada através do uso de uma câmara de ionização do tipo lápis e para o PDA foi utilizado um aparelho PTW, nos quatro protocolos. Na avaliação da acurácia das mensurações lineares, não houve diferença significativa entre o EM dos protocolos, o que mostra que eles se comportaram iguais quanto à realização de medidas lineares. O EM foi bastante reduzido, uma vez que a média da diferença entre os valores obtidos nas imagens e na mandíbula seca foi menor do que 1mm para todos os protocolos e, em sua grande maioria, sofreram variação para menos. Para avaliação das doses referenciais, detectou-se diferença estatisticamente significante (p<0,001) entre os protocolos, para avaliação do PDA e DEP, sendo que os protocolos p3 e p4 apresentaram doses significantemente menores. A diferença significativa presente entre os protocolos está diretamente relacionada à diferença da miliamperagem e do tempo de varredura. Sendo assim, o uso dos protocolos p3 e p4 devem ser, preferencialmente, indicados na avaliação de mensurações lineares, uma vez que a dose de radiação é significantemente menor quando comparado aos protocolos p1 e p2, sem perda de acurácia das mensurações verticais e horizontais. / Salvador

Thesis (MTech Biomedical Technology)--Cape Peninsula University of Cape Town, 2005 / In clinical radiotherapy, experiments are performed to determine optimal conditions of the radiation prior to radiotherapy. These experiments focus on the relative biological effectivness(RBE) determination and are predominantly applied in high linear energy transfer (LET) radiations i.e. fast neutrons, as the RBE values for such radiations vary greatly. In general, the RBE of a certain radiation relative to a given reference radiation flCo gamma) varies widely with the energy, dose, dose rate, fractionation, type of tissue and end-point used. Experience with neutron therapy at iThemba LABS has shown that treatment with more fractions and lower doses per fraction may be beneficial for some patients. To calculate the iso-effective treatment dose needed, an appropriate alp ratio for early effects is needed. In this study, the repair of mouse jejunum was measured for split-dose irradiations to determine if a suitable alP ratio for neutrons could be estimated using the known value for gamma rays and the applicable RBE.. Crypt stem cell survival was measured 3.5 days after split-dose exposures to p(66)/Be neutrons and 6OCo gamma rays. Dose response curves for both treatment modalities and for both acute and fractionated exposures were constructed by counting crypts of Leiberkhiin at the base of the villi in haematoxylin and Eosin-stained sections of mouse jejunum. Using a RBE value of 1.64 and an alP ratio of 7Gy noted for tbe fractionated photon exposures, an alP ratio of 11.5 IV could be estimated for neutrons.

Thesis (DTech (Biomedical Technology))--Cape Technikon, 2001 / Ionising radiation has the ability to induce, inter alia, DNA damage and is well established as a causative agent of carcinogenesis and mutagenesis. The effects of high doses of short duration have been well documented, whereas the effects of continuous exposure to low doses of ionising radiation have not, nor are they as clearly understood and current risk estimates are largely extrapolated from high-dose data of atomic bomb survivors. This study evaluated the clastogenic effects of low dose ionising radiation on a population of bats (Chiroptera) residing in an abandoned monazite mine. Bats were sampled from two areas in the mine, with external radiation levels measuring around 20 µSv/h (low dose) and 100 µSv/h (high dose). A control group of bats was collected from a cave with no detectable radiation above normal background levels. The most frequently encountered genetic event in human malignancy is the alteration of the p53 gene. Mutant p53 proteins have a longer half-life than the wild-type variant and accumulate to high levels in the nucleus of tumour cells. The study showed that not only was there a significant increase in p53 positive cells of radiation exposed bats, but also in the degree of positivity, especially in the cells lining the bronchioles of the lungs. Although experimental studies have shown that exposure to radiation may lead to the onset of fibrosis and an inflammatory response in the lung and other tissues, the magnitude of the dose exposure was not comparable to this study and histological examination of bat lung and liver tissues showed no morphological changes in radiation exposed bats when compared to the control group. It has been documented that chronic radiation exposures may give rise to a number of specific haematological defects which are collectively termed "preleukemia" or myelodysplastic syndrome. Full blood counts on bat samples showed a significant decrease in the MCV indicating microcytic erythrocytes from the radiation exposed bats. Differential counts performed on the peripheral blood of the bats showed a marked neutropenia. Neutrophils also showed marked dysplasia including psuedo-Pelger Huet cells in radiation-exposed bats. Cytochemical analysis using DAB myeIoperoxidase showed that control bats had hypogranular neutrophils andradiation-exposedbats had largely '1granularneutrophils. Bonemarrow biopsies were taken from both control and radiation-exposed bats and evaluated for ceIlularity, granulocyte: lymphocyte: erythrocyte (GLE) ratio and megakaryocyte morphology. A hypocelIular bone marrow, a decreased granulocytic haematopoeisis and dysplastic megakaryocyte morphology were observed in radiation-exposed bats. Mineralisation of bone osteoid was determined using image analysis and showed a highly significant decrease in the bone matrix from radiation-exposed bats. All haematological features observed are congruent with current literature describing secondary (radiation-induced) myelodysplastic syndrome.

Thesis submitted in fulfilment of the requirements for the award of the degree of Master of Technology Radiography (Diagnostic) in the Faculty of Health and Wellness Sciences at the Cape Peninsula University of Technology 2009 / Since their discovery in 1895, the use of x-rays is continuously evolving in medicine making the diagnosis of injuries and diseases more practicable. It is therefore not surprising that x-rays contribute 90% of the radiation dose to the population from manmade sources (DWP, 1992). Moreover, these radiation doses are associated with both fatal and non-fatal cancer risk that is detrimental to adults between 20 to 60 years (Wall, 1996). Radiation dose to individuals therefore needs to be actively monitored in order to minimise such risk. Barium contrast examinations were characterised as one of the radiological examinations that contributed enormously to the collective dose to the patients in the radiology department (DWP, 1992). Determining the diagnostic reference levels of such examinations would reduce the over-exposure of individuals to ionising radiation. Currently in South Africa (SA), there are no diagnostic dose reference levels for barium meal (BaM) and barium enema (BaE) examinations. This study therefore investigated the radiation doses delivered to patients referred for BaM and BaE, obtained potential regional reference doses for these examinations, compared the radiation doses obtained with those from similar dosimetry studies and investigated sources of dose variation among the study sites. A total of 25 BaM and 30 BaE patients in the age range 18 to 85 years, weighing 50 kg to 90 kg, at 3 hospitals in the Western Cape, SA were investigated. The radiation dose to the patients was measured using Dose Area Product (DAP) meters that were permanently fitted onto fixed fluoroscopy units at these 3 hospitals. The third quartile DAP values were 20.1 Gycm2 and 36.5 Gycm2 for BaM and BaE respectively. The median DAP values were 13.6 Gycm2 and 27.8 Gycm2 for BaM and BaE respectively. The median values were recommended as the potential Diagnostic Reference Levels for BaM and BaE as they are less affected by outlying values of under or over- weight (Yakoumakis, Tsalafoutas, Sandilos, Koulentianos et al, 1999). The weights of the patients, fluoroscopy time, the number of images obtained, the use of digital or conventional fluoroscopy equipment and the level of training of the radiologists were the factors considered for dose variation among the 3 hospitals.

Orientador: Sergio Santos Muhlen / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-14T23:21:55Z (GMT). No. of bitstreams: 1 Ferraz_MarianaSacriniAyres_M.pdf: 4432455 bytes, checksum: 653b956278da2f0d25423b525a3311d0 (MD5) Previous issue date: 2009 / Resumo: Exames de cateterismo que utilizam fluoroscopia, como a angioplastia coronariana, são responsáveis por altas doses de radiação (maiores que na radiologia convencional), tanto para os pacientes como para a equipe médica. O uso intensivo dos raios X faz com que aumentem os riscos radiológicos, em decorrência da alta exposição cumulativa durante a vida dos cardiologistas intervencionistas e suas equipes. Os principais riscos decorrentes de altas doses de raios X são: câncer, cataratas, malformações e danos ao feto de mulheres grávidas. A geração de raios X com tecnologia pulsada, que se tornou disponível aos hospitais, representa uma potencial redução da dose de radiação recebida pela equipe profissional. O montante de redução da dose ainda é objeto de controvérsias na literatura, mas alguns autores descrevem reduções de até 70%. Este trabalho teve por objetivo o estudo da dose ocupacional no Laboratório de Cateterismo Cardíaco da UNICAMP. Foram comparadas as doses recebidas pela equipe para a fluoroscopia contínua e pulsada, e a diminuição proporcionada pela troca do equipamento de fluoroscopia contínua pelo pulsado no Laboratório foi quantificada. As diminuições encontradas para os médicos, principal e auxiliar, foram de 5,2% e 13,7% respectivamente. Para os enfermeiros e auxiliares de enfermagem foram de 7,5% e 8,2%. Além disso, foram calculadas as doses efetivas por procedimento para cada profissional, e foi feita uma análise dos dados dos dosímetros termoluminescentes usados em todo o período de funcionamento do Laboratório. Em conclusão, a diminuição proporcionada pela tecnologia pulsada não foi significativa, e neste trabalho são propostas novas estratégias para reduzir a dose ocupacional no Laboratório de Cateterismo. / Abstract: Procedures of catheterism using fluoroscopy, as coronary angioplasty, are responsible for high doses of radiation (higher than conventional radiology), not only for patients but for the medical staff as well. The intensive use of X-rays increases radiological risks, as a consequence of cumulative exposition, for cardiologists and their teams. The main risks resulted from high doses of X-rays are: cancer, cataracts, malformations, and damage to the fetuses of pregnant women. The production of X-rays with pulsed technology, which is now available in many hospitals, implies a potential reduction of the radiation dose received by the medical staff. The amount of dose reduction is still controversy in literature, but some authors report reductions up to 70%. This work aimed at study occupational dose in the Cardiac Catheterism Laboratory of UNICAMP. The doses received by the medical staff on the continuous and pulsed fluoroscopy modes were compared, and the dose reduction consequent to the change of technologies in the Laboratory (from continuous to pulsed fluoroscopy) was measured. The reductions found for main and auxiliary physicians were 5.2% and 13.7%, respectively. For nurses, auxiliary nurses and technicians, the reductions were 7.5% to 8.2%. Moreover, the effective dose of each procedure for each professional was calculated and data analysis of the thermoluminescent dosimeters used in the whole Laboratory working periods was made. In conclusion, the dose reduction caused by pulsed technology was not significant, and new strategies to reduce occupational doses in the Catheterism Laboratory are proposed. / Mestrado / Engenharia Biomedica / Mestre em Engenharia Elétrica

Radiography is a common radiologic investigation despite abundant evidence of its limited diagnostic value. On the other hand, computed tomography (CT) has a high diagnostic value and is widely considered to be among the most important advances in medicine. However, CT exposes patients to a higher radiation dose and it might therefore not be acceptable simply to replace radiography with CT, despite the powerful diagnostic value of this technique. At the expense of reduced CT image quality, which could be adjusted to the diagnostic needs, low-dose CT of abdomen and lumbar spine can be performed at similar dose to radiography. The aim of the current thesis project was to evaluate low-dose CT of the abdomen and lumbar spine and to compare it with radiography. The hypothesis was that CT would give better image quality and diagnostic information compared to radiography at similar dose levels. Firstly, the diagnostic accuracy of low-dose CT of the abdomen was evaluated. Results showed that low-dose CT of abdomen has a high sensitivity and specificity compared to radiography, i.e., it has higher diagnostic accuracy. Similar results were obtained from our systematic review. Secondly, in a phantom study, an ovine phantom was scanned at various CT settings. The image quality was evaluated to obtain a protocol for the optimal settings for low-dose CT of lumbar spine at 1 mSv. This new protocol was then used in a clinical study to assess the image quality of low-dose CT of the lumbar spine and compare it to radiography. Results showed that low-dose CT has significantly better image quality than radiography. Finally, the impact of Iterative reconstruction (IR) on image quality of lumbar spine CT was tested. Iterative reconstruction is a recent CT technique aimed to reduce radiation dose and/or improve image quality. The results showed that the use of medium strength IR levels in the reconstruction of CT image improves image quality compared to filtered back projection. In conclusion, low-dose CT of the abdomen and lumbar spine, at about 1 mSv, has better image quality and gives diagnostic information compared to radiography at similar dose levels and it could therefore replace radiography.

Orientador: Fernando Cendes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-28T02:24:31Z (GMT). No. of bitstreams: 1 Altemani_JoaoMauricioCarrasco_D.pdf: 1901312 bytes, checksum: bcace160b968ce113f8f422a3db9339b (MD5) Previous issue date: 2015 / Resumo: Esse trabalho foi realizado para avaliar as doses de radiação absorvidas em exames de tomografia computadorizada em um hospital geral que atende uma grande população no Brasil. O FDA (Food and Drug Administration) considera que exames de CT com a absorção de uma dose efetiva de 10 mSv podem ser associados com um aumento na probabilidade de desenvolver um câncer fatal na proporção de 1/2000. Foram revisados 1352 relatórios de exames de tomografia computadorizada, provenientes de dois aparelhos, um com 16 e outro com 64 detectores. No aparelho de 16 detectores doses absorvidas ? 10 mSv foram observadas em 182 casos de um total de 326 pacientes (56%), enquanto no aparelho de 64 detectores essas doses foram observadas em 517 casos de um total de 996 pacientes (52%). Doses absorvidas > 100 mSv foram observadas em 16% de todos pacientes. Em ambos aparelhos , exames de abdome e de tórax + abdome apresentaram doses significantemente maiores que nos exames de pescoço, cabeça e tórax. Exames de abdome e tórax + abdome realizados com espessura de 1,25 mm no tomógrafo de 16 detectores e com 1,0 mm no aparelho de 64 detectores mostraram uma significante redução da dose absorvida em comparação com os mesmos tipos de exame realizados com espessura de 0,5 mm no aparelho de 64 detectores. Os exames de tórax realizados com espessura de 1,25 mm no tomógrafo de 16 detectores também mostraram uma significante diminuição da dose absorvida em comparação ao mesmo tipo de exame realizado no aparelho de 64 detectores com cortes de 0,5 mm. O aumento da espessura dos cortes tomográficos não causou uma significativa alteração na qualidade das imagens. Em conclusão, exames de tomografia computadorizada são frequentemente associados com altas doses de radiação absorvida indicando que os protocolos de exames devem ser reavaliados. Para exames de tomografia de abdome e de tórax + abdome , o aumento da espessura dos cortes pode proteger os pacientes de altas doses de radiação desnecessárias / Abstract: This study was conducted to evaluate the absorbed radiation doses in CT examinations in a general hospital that serves a large population in Brazil. The Food and Drug Administration (FDA) considers that CT examination with an effective dose of 10 mSv may be associated with an increase in the possibility of fatal cancer of around 1/2000. CT examinations of 1352 patients performed in two types of CT equipment (with 16 and 64 detectors) were reviewed. In the 16 detector CT scanner, an absorbed dose ?10 mSv was detected in 182 out of 326 patients (56%) whereas in the 64 detector CT scanner, in 517 out of 996 (52%). Absorbed dose > 100 mSv was seen in 16% of all patients. In both CT scanners, examinations of abdomen and thorax+ abdomen presented an absorbed dose significantly higher than neck, head and thorax. Examinations of abdomen and thorax+ abdomen performed with slices of 1,25 mm in the 16 detector CT scanner and with 1,0 mm in the 64 detector CT scanner showed a significant reduction of the absorbed dose in comparison to the same type of examination with slices of 0.5 mm in the 64 detector CT scanner. The examinations of thorax performed with slices of 1,25 mm in the 16 detector scanner also showed a significant reduction of the absorbed dose in comparison to the examinations performed with slices of 0,5 mm in the 64 detectors scanner. The increase of the slice thickness did not lead to noticeable alteration of the image quality. In conclusion, CT examinations were often associated with high doses of absorbed radiation indicating that the protocols of the examinations should be reevaluated. For CT examinations of abdomen and thorax+abdomen, the increase of the slice thickness can protect patients from unnecessarily high doses of radiation / Doutorado / Fisiopatologia Médica / Doutor em Ciências

The International Commission on Radiological Protection (ICRP) determines the policy regarding radiation safety internationally. To the ICRP, hereditary changes as a result of either high or low doses, are of a major concern. The SA Forum for Radiation Protection recommended that a research project to determine the genetically-significant dose (GSD) for the South African population should be done as such a project has never been undertaken to date. This term was at first defined by UNSCEAR in 1958. The National Radiological Protection Board derived a formula from this definition as shown in the NRPB Report, NRPB-R106 (1980). This formula was implemented in the project. It combines the frequency of radiological examinations obtained during the country-wide survey and estimates of gonadal doses for different examination types, together with population and child expectancy data. New procedures, techniques and data processing that were relevant to this project had to be developed because the available information and conditions are unique to South Africa. The task was set to find a model in order to draw the best representative sample of the population and it was determined in a unique way, namely the so-called Dollar Unit Sampling method. A sample of 27 institutions out of a possible 292 (9%) was drawn in comparison, e.g., with the 8% of France and 8% in Great Britain. It was necessary to rely mainly on the calculation of gonad doses due to a shortage of manpower, contrary to other countries that were able to physically measure doses. Information obtained in the survey was used in this regard. The "RADCOMP Entrance Skin Exposure Software Program " of Nuclear Associates was used to produce parametric Free Air Exposure tables based on doses from Table B.3, NCRP Report No. 102. After the skin entrance doses were calculated, it was possible to calculate the gonad doses. A computer program was obtained from the Food and Drug Administration in the USA for this purpose. Data analysis was performed by means of the software package Microsoft Excel version 4.0. The above-mentioned formula was used in order to obtain the final results. The GSD for the total SA-population was calculated as 94.6 μGy. The breakdown of the GSD for the various South African race groups was Asian - 229.0 μGy, Black - 66.5 μGy, Coloured - 112.2 μGy and White - 463.4 μGy.

In the investigation of radiation accidents, it is of great importance to estimate the dose absorbed by exposed persons in order to plan their therapy. Although occasionally in these situations physical dose measurements are possible, most often biological methods are required for dose estimation. The aim of this investigation was to assess the suitability of the cytokinesis blocked (CB) micronucleus assay as a biodosimetric method using lymphocytes irradiated in vivo. The approach adopted to achieve this was to estimate whole body doses by relating micronuclei yields in patients undergoing radiotherapy treatment with an in vitro radiation dose-response curve. These biologically derived estimates were then compared with the corresponding doses obtained by physical measurement and calculation. As a first approach a study was performed of the in vitro dose-response of gamma-ray induced micronuclei following cytokinesis-block in the lymphocytes of peripheral blood samples obtained from 4 healthy donors. The results indicated that the distribution of the induced micronuclei were overdispersed. Furthermore, a linear dose-response relationship was established when a curve was fitted to the data by an iteratively reweighted least squares method. By means of an analysis of covariance it was demonstrated that this result is in agreement with the dose-response relationships found by various other workers (Fenech et al., 1985; Fenech et al., 1986; Fenech et al., 1989; Balasem et al., 1992, and Slabbert, 1993). To assess the suitability and accuracy of dose assessment using the CB micronucleus assay for in vivo exposure of lymphocytes, blood samples obtained from 8 patients undergoing radiotherapy before, during and after treatment were examined. The physical doses of these patients were determined according to conventional radiation treatment plans and cumulative dose-volume histograms. The dose-volume histograms permitted calculation of integral doses and subsequently the estimate of equivalent whole-body doses. The results of the CB micronucleus assay applied to peripheral blood lymphocytes of 6 patients undergoing fractionated partial-body irradiation showed a dose-related increase in micronucleus frequency in each of the patients studied. This demonstrated that micronuclei analysis may serve as a quantitative biological measure of such exposures. The pooled data of these patients compared to the pooled data of the healthy donors show that there was no statistically significant difference between in vitro and in vivo results, however a slightly lower induced micronuclei frequency was observed after in vivo exposure. When the biological dose estimates for equivalent whole-body doses obtained from the in vitro dose response curve were compared with calculated physical doses, it was found that: biologically estimated dose = 0.936 physical dose. However, there was inadequate statistical evidence to discard the hypothesis that the gradient of the equation was equal to one. Therefore, the analysis of micronuclei induced in lymphocytes in vivo yields highly quantitative information on the equivalent whole-body dose. The negative binomial method was used for analysing the micronucleus data from two patients who received single, relatively larger tumour doses of 10 Gy each, with the objective to obtain estimates of the exposed body fraction and the dose to this fraction. The dose estimates to the irradiated volume were found to be within 30% of the physical tumour dose. The irradiated volume estimates seemed to be higher than the physically calculated volumes but by discarding the correction for the loss of cells due to interphase death the agreement was good between the physically and biologically determined integral doses. This study has revealed that the CB micronucleus assay appears to offer a reliable, consistent and relatively rapid biological method of whole body dose estimation. It is recognised that further corroborative work using the techniques described in this thesis is required for estimating localized exposure.