Modeling the influence of formalin fixation time on the elemental constitution of human tissues

• Autor(a) principal: Silva, João Carlos Tomás da
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/152019
• topic: Cancer; Muscle; μEDXRF; μXRF; Trace Elements; Calibration Curves; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Cancer is a leading cause of death worldwide, accounting for nearly 9.6 million deaths. Therefore, an early and accurate diagnosis is essential. Trace elements are essential and are linked with toxicity when they exist in abnormal quantities. Thus, understanding the mechanisms of assimilation/accumulation of trace elements may be indicative of the genesis or progression of certain diseases, such as carcinogenesis. X-rays have been employed in the medical system since its discovery, particularly for diagnostics and treatments. Micro Energy Dispersive X-ray Fluorescence (μEDXRF) is used as a multielement analysis technique of trace elements, once it measures non- destructively actual tissue levels of elements in very small portion of tissue, and it was the chosen one for this Master Thesis. Previous studies show that the formalin fixation time influences the elemental composition present on the tissue, focusing on the drastic decrease of K and Cl after 48 hours. In order to have an accurate quantification of this elements, we need to study the influence of formalin fixation time on tissues. In this work, 6 sets of muscle tissues, from Instituto Português de Oncologia (IPO), submitted to different fixation times in formalin were analyzed with the goal to param- eterize the influence of formalin fixation time on the elemental constitution of human tissues, focusing on 9 trace elements - K, Zn, Cl, P, S, Cu, Fe, Mn and Ca. The quantitative analysis was done using Certified Reference Materials (CRMs) to build elemental cali- bration curves. All the data was treated in different ways, namely with ROOT software - removing background and identifying each elemental peaks - and with the Compton-to- Rayleigh Ratio correction, in order to minimize errors and improve accuracy. Statistical tests, Shapiro-Wilk was performed to test the normality of the distributions of each ele- ment and Kruskal-Wallis ANOVA to compare the tissues with different fixation times. The results obtained, confirmed what it was expected, showing that the K and Cl concentrations dramatically decrease in the first 3 hours of formalin fixation time.