Avaliação dosimétrica em tumores de mama: comparação de três técnicas

Objetivo – Comparar a técnica convencional, a técnica de energias mistas e a técnica field-in-field com energias mistas, verificando a dose recebida nos órgãos de risco e no volume alvo. Metodologia – Quinze doentes com carcinoma da mama esquerda classificadas de T1-T3N0M0 foram tratadas com cirurgia conservadora da mama, seguida de radioterapia pós-operatória. Para cada doente realizaram-se 3 planeamentos dosimétricos, sendo que cada um deles diz respeito a uma das diferentes técnicas em estudo. Através dos HDV gerados avaliaram-se a Dmáx, Dmed, Dmín, D95%, D3% e a homogeneidade da dose no volume alvo, bem como a dose nos órgãos de risco. Utilizou-se o teste de Friedman para verificar a significância do estudo, com um intervalo de confiança de 95%. Resultados – Relativamente ao pulmão esquerdo e ao coração obtiveram-se, com a técnica field-in-field com energias mistas, doses inferiores em comparação com as outras duas técnicas. Para a Dmáx e a homogeneidade de dose no PTV, a técnica field-in-field com energias mistas revelou-se mais eficaz, comparativamente às outras técnicas. No entanto, verificou-se uma melhor cobertura de dose no PTV com a técnica convencional. Considerações finais – A técnica field-in-field com energias mistas permite uma redução da dose nos órgãos de risco, uma redução significativa da Dmáx no PTV e melhora a homogeneidade da dose, comparativamente com as outras técnicas. Os resultados obtidos com a técnica field-in-field com energias mistas apontam para a redução dos efeitos secundários provocados pelo tratamento. ABSTRACT - Purpose – To compare the conventional technique, the technique of mixed energies and the technique field-in-field with mixed energies, checking the received dose in organs at risk and target volume. Methods – Fifteen patients with carcinoma of the left breast classified as T1-T3N0M0 were treated with breast-conserving surgery, followed by postoperative radiotherapy. For each patient were carried out three dosimetric plannings, each one of them concerns the different techniques under study. Through the DVH generated to evaluate Dmax, Dmed, Dmin, D95%, D3% and the homogeneity of the target volume dose, well as the dose in organs at risk. We used the Friedman test to assess the significance of the study, with a confidence interval of 95%. Results – For the left lung and heart were obtained with the technique field-in-field with mixed energies, lower doses compared with the other two techniques. For the Dmax and the homogeneity of the PTV dose, the technique field-in-field with mixed energies was more effective compared to other techniques. However, there was a better coverage of the PTV dose with conventional technique. Conclusions – The technique field-in-field with mixed energy allows a reduction in dose for organs at risk, a significant reduction Dmax in PTV and improves the homogeneity of the dose compared with other techniques. The results obtained with the technique field-in-field with mixed energy indicate to reduce the side effects caused by the treatment.

Quantificação por imagem ponderada em difusão (DWI) das lesões tumorais da mama

Introdução – A técnica de Difusão por Ressonância Magnética (RM), ao avaliar o movimento das moléculas de água nos tecidos, permite inferir sobre a arquitetura dos mesmos, em particular relativamente à celularidade, volume celular e permeabilidade das membranas. O Coeficiente de Difusão Aparente (ADC) é um parâmetro quantificável da imagem ponderada em difusão (DWI). A sua análise poderá fornecer informação clínica adicional sobre estas lesões, sobretudo em relação à sua caracterização histológica. Objetivos – Caracterizar e diferenciar tipos e alguns subtipos de lesões mamárias através da análise do ADC. Metodologia – 20 Mulheres com 23 lesões mamárias foram submetidas a RM mamária: 3 lesões benignas (3 Fibroadenomas-FA) e 20 malignas (16 Carcinomas Ductais Invasivos-CDI, 2 Carcinomas Ductais In Situ-CDIS e 2 Carcinomas Invasivos Lobulares-CLI). Num equipamento 1.5T aplicou-se uma sequência de Difusão (b=0,50,250,500,750,1000 s/mm2). Obteve-se o ADC através do ajuste exponencial da intensidade de sinal das lesões em função do valor de b, fazendo-se corresponder os valores de ADC à respetiva caracterização histológica e posterior comparação com a literatura. Resultados e Discussão – As lesões malignas apresentaram ADCs significativamente (p=0,014) inferiores [(0,94±0,22)x10-3 mm2/s] aos das benignas [(1,43±0,25)x10-3 mm2/s]. A justificação pode residir no aumento da celularidade e consequente restrição da Difusão que se observa nas lesões malignas. Os CDI apresentaram ADCs baixos [(0,88±0,17)x10-3 mm2/s], enquanto que os CDIS apresentaram ADCs mais elevados [(1,33±0,29)x10-3 mm2/s]. Estes resultados estão de acordo com o facto dos CDIS estarem limitados aos ductos mamários, mantendo-se menos alterada a estrutura do tecido adjacente e resultando numa menor restrição à difusão que nos CDI. Verificaram-se diferenças significativas entre FA e CDI (p=0,010) e entre CDI e CDIS (p=0,049). Conclusões – O ADC possibilita a diferenciação entre lesões mamárias benignas e malignas, bem como entre alguns tipos histológicos. O desenvolvimento deste conceito pode representar um avanço no papel da RM na avaliação destas neoplasias. ABSTRACT - Introduction – The Magnetic Resonance (MR) diffusion technique measures the movement of water molecules in tissues. Therefore, it provides useful information about tissue architecture, specially regarding tissue cellularity, cell volume and membrane permeability. The quantification of diffusion weighted imaging (DWI) data is done by measuring the so-called. Apparent Diffusion Coefficient (ADC). This parameter provides additional clinical information about breast lesions, and potentially allows for in-vivo histological characterization. Purpose – To characterize and differentiate breast lesions through ADC analysis. Methodology – The study comprised 20 women, with 23 breast lesions: 3 benign lesions - 3 Fibroadenomas (FA); and 20 malignant - 16 Invasive Ductal Carcinomas (CDI), 2 Ductal Carcinomas In Situ (CDIS), 2 Invasive Lobular Carcinoma (CLI). On a 1.5T equipment a diffusion-weighted sequence with 6 b-values (b=0,50,250,500,750,1000 s/mm2) was used to examine the patients. ADC was obtained by fitting an exponential to data of lesion signal intensity vs. b values. A correspondence of ADC values to histological lesion characterization was done and finally, the results were comparison with the literature. Results and Discussion – Malignant lesions showed inferior ADCs significantly (p=0.014) lower ((0.94±0.22)x10-3 mm2/s) than the benign lesions ((1.43±0.25)x10-3 mm2/s). This may be associated to increasead cellularity in malignant lesions, which result in higher tissue restriction to diffusion. CDI showed low ADC values ((0.88±0.17)x10-3 mm2/s), while the CDIS showed higher ADCs ((1.33±0.29)x10-3 mm2/s). These results agree with the fact that CDIS are limited to mammary ducts, maintaining a less altered neighboring tissue structure, which results in a lower restriction to diffusion than observed in CDI. Significant differences between FA and CDI (p=0.010) and between CDI and CDIS (p=0.049) were observed. Conclusion – The ADC parameter is able to differentiate between malignant and benign breast lesions, as well as between some histological types.

Prognóstico de pacientes com tumor de Wilms unilateral no Rio de Janeiro, 1990-2000

OBJETIVO: Analisar a sobrevida e os principais fatores prognósticos entre os pacientes com tumor de Wilms unilateral. MÉTODOS: A coorte de estudo incluiu 132 casos de tumor de Wilms unilateral em menores de 15 anos de idade matriculados em serviço de oncologia pediátrica, de janeiro de 1990 a dezembro de 2000. Curvas de sobrevida foram confeccionadas utilizando-se o método de Kaplan-Meier e fatores prognósticos foram analisados pelo modelo de riscos proporcionais de Cox. RESULTADOS: A estimativa de sobrevida global em cinco anos foi 84,6%. As probabilidades de sobrevida para os estádios I, II, III e IV foram de 100%; 94,2%; 83,2% e 31,3%, respectivamente. A taxa de sobrevida para os pacientes com: histologia favorável foi de 89,4%, para aqueles com anaplasia focal 66,7 % e com anaplasia difusa 40%. Todos os pacientes com doença em estádio IV e anaplasia difusa foram a óbito (n=4). Todos os pacientes com doença em estádio I, independente da histologia, permaneceram vivos até o final do período de seguimento. CONCLUSÕES: Entre as variáveis escolhidas para o modelo final apenas o estadiamento e a histologia permaneceram associados ao elevado risco de óbito enquanto que os casos na faixa etária entre 24 e 47 meses apresentaram melhor prognóstico que os demais. Esses resultados mostram a importância do diagnóstico em fases iniciais da doença e que a histologia é fundamental para orientar a terapia adequada.

Topological Complexity and Predictability in the Dynamics of a Tumor Growth Model with Shilnikov's Chaos

Dynamical systems modeling tumor growth have been investigated to determine the dynamics between tumor and healthy cells. Recent theoretical investigations indicate that these interactions may lead to different dynamical outcomes, in particular to homoclinic chaos. In the present study, we analyze both topological and dynamical properties of a recently characterized chaotic attractor governing the dynamics of tumor cells interacting with healthy tissue cells and effector cells of the immune system. By using the theory of symbolic dynamics, we first characterize the topological entropy and the parameter space ordering of kneading sequences from one-dimensional iterated maps identified in the dynamics, focusing on the effects of inactivation interactions between both effector and tumor cells. The previous analyses are complemented with the computation of the spectrum of Lyapunov exponents, the fractal dimension and the predictability of the chaotic attractors. Our results show that the inactivation rate of effector cells by the tumor cells has an important effect on the dynamics of the system. The increase of effector cells inactivation involves an inverse Feigenbaum (i.e. period-halving bifurcation) scenario, which results in the stabilization of the dynamics and in an increase of dynamics predictability. Our analyses also reveal that, at low inactivation rates of effector cells, tumor cells undergo strong, chaotic fluctuations, with the dynamics being highly unpredictable. Our findings are discussed in the context of tumor cells potential viability.

Análise de investimentos em ativos reais – Volume 1: abordagem convencional

Estrutura da obra: CAPÍTULO I: Enquadramento e conceitos básicos CAPÍTULO II: Previsão de fluxos de capital CAPÍTULO III: O custo do capital CAPÍTULO IV: Critérios de avaliação e decisão de investimentos CAPÍTULO V: Casos Práticos Globais

Análise de investimentos em ativos reais – volume 2: análise de risco e incerteza

Estrutura da obra CAPÍTULO I: Introdução à análise de risco e incerteza CAPÍTULO II: Técnicas tradicionais de análise de risco e incerteza CAPÍTULO III: Introdução às opções reais CAPÍTULO IV: Casos Práticos Globais

Radioterapia adaptativa: utilização do cone-beam computed tomography para o cálculo de dose em radioterapia

Mestrado em Radiações Aplicadas às Tecnologias da Saúde - Ramo de especialização: Terapia com Radiações

Dosimetria e análise de incertezas em braquiterapia ginecológica

Mestrado em Radiações Aplicadas às tecnologias da Saúde

Aurícula direita: mecânica e sobrecarga de volume

Mestrado em Tecnologia de Diagnóstico e Intervenção Cardiovascular - Ramo de especialização: Ultrassonografia Cardiovascular

Dosimetric effect of tissue heterogeneity for 125I prostate implants

Aim - To use Monte Carlo (MC) together with voxel phantoms to analyze the tissue heterogeneity effect in the dose distributions and equivalent uniform dose (EUD) for (125)I prostate implants. Background - Dose distribution calculations in low dose-rate brachytherapy are based on the dose deposition around a single source in a water phantom. This formalism does not take into account tissue heterogeneities, interseed attenuation, or finite patient dimensions effects. Tissue composition is especially important due to the photoelectric effect. Materials and Methods - The computed tomographies (CT) of two patients with prostate cancer were used to create voxel phantoms for the MC simulations. An elemental composition and density were assigned to each structure. Densities of the prostate, vesicles, rectum and bladder were determined through the CT electronic densities of 100 patients. The same simulations were performed considering the same phantom as pure water. Results were compared via dose-volume histograms and EUD for the prostate and rectum. Results - The mean absorbed doses presented deviations of 3.3-4.0% for the prostate and of 2.3-4.9% for the rectum, when comparing calculations in water with calculations in the heterogeneous phantom. In the calculations in water, the prostate D 90 was overestimated by 2.8-3.9% and the rectum D 0.1cc resulted in dose differences of 6-8%. The EUD resulted in an overestimation of 3.5-3.7% for the prostate and of 7.7-8.3% for the rectum. Conclusions - The deposited dose was consistently overestimated for the simulation in water. In order to increase the accuracy in the determination of dose distributions, especially around the rectum, the introduction of the model-based algorithms is recommended.

Analysis of the respiratory dynamics during normal breathing by means of pseudo phase plots and pressure-volume loops

This paper reports on the analysis of tidal breathing patterns measured during noninvasive forced oscillation lung function tests in six individual groups. The three adult groups were healthy, with prediagnosed chronic obstructive pulmonary disease, and with prediagnosed kyphoscoliosis, respectively. The three children groups were healthy, with prediagnosed asthma, and with prediagnosed cystic fibrosis, respectively. The analysis is applied to the pressure–volume curves and the pseudophaseplane loop by means of the box-counting method, which gives a measure of the area within each loop. The objective was to verify if there exists a link between the area of the loops, power-law patterns, and alterations in the respiratory structure with disease. We obtained statistically significant variations between the data sets corresponding to the six groups of patients, showing also the existence of power-law patterns. Our findings support the idea that the respiratory system changes with disease in terms of airway geometry and tissue parameters, leading, in turn, to variations in the fractal dimension of the respiratory tree and its dynamics.

Intrinsic fractal dynamics in the respiratory system by means of pressure-volume loops

This contribution presents novel concepts for analysis of pressure–volume curves, which offer information about the time domain dynamics of the respiratory system. The aim is to verify whether a mapping of the respiratory diseases can be obtained, allowing analysis of (dis)similarities between the dynamical pattern in the breathing in children. The groups investigated here are children, diagnosed as healthy, asthmatic, and cystic fibrosis. The pressure–volume curves have been measured by means of the noninvasive forced oscillation technique during breathing at rest. The geometrical fractal dimension is extracted from the pressure–volume curves and a power-law behavior is observed in the data. The power-law model coefficients are identified from the three sets and the results show that significant differences are present between the groups. This conclusion supports the idea that the respiratory system changes with disease in terms of airway geometry, tissue parameters, leading in turn to variations in the fractal dimension of the respiratory tree and its dynamics.

Programa de controlo de acessos com configuração de regras em XML: Volume 1

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

Characterization of the glycosylation of human tumor cells

Ovarian cancer is within the most lethal gynecological malignancies in woman. Therefore, many investigators study its biological aspects with the purpose of discovering more rapid diagnostic methods and efficient treatment. Resembling many other tumors, in ovarian cancer, aberrant glycosylation occurs with the appearance of novel or altered carbohydrate structures. These can be terminal motifs, such as the Lewis determinants, or entire carbohydrate sequences, which have been related to tumorigenesis and its outcome.(...)

18F-FDG measurement in primary lung cancer: SUV normalization to different distribution volumes

Introduction: Standard Uptake Value (SUV) is a measurement of the uptake in a tumour normalized on the basis of a distribution volume and is used to quantify 18F-Fluorodeoxiglucose (FDG) uptake in tumors, such as primary lung tumor. Several sources of error can affect its accuracy. Normalization can be based on body weight, body surface area (BSA) and lean body mass (LBM). The aim of this study is to compare the influence of 3 normalization volumes in the calculation of SUV: body weight (SUVW), BSA (SUVBSA) and LBM (SUVLBM), with and without glucose correction, in patients with known primary lung tumor. The correlation between SUV and weight, height, blood glucose level, injected activity and time between injection and image acquisition is evaluated. Methods: Sample included 30 subjects (8 female and 22 male) with primary lung tumor, with clinical indication for 18F-FDG Positron Emission Tomography (PET). Images were acquired on a Siemens Biography according to the department’s protocol. Maximum pixel SUVW was obtained for abnormal uptake focus through semiautomatic VOI with Quantification 3D isocontour (threshold 2.5). The concentration of radioactivity (kBq/ml) was obtained from SUVW, SUVBSA, SUVLBM and the glucose corrected SUV were mathematically obtained. Results: Statistically significant differences between SUVW, SUVBSA and SUVLBM and between SUVWgluc, SUVBSAgluc and SUVLBMgluc were observed (p=0.000<0.05). The blood glucose level showed significant positive correlations with SUVW (r=0.371; p=0.043) and SUVLBM (r=0.389; p=0.034). SUVBSA showed independence of variations with the blood glucose level. Conclusion: The measurement of a radiopharmaceutical tumor uptake normalized on the basis of different distribution volumes is still variable. Further investigation on this subject is recommended.