Correlação entre as variações na concentração de elementos-traço e densidade eletrônica em tumores mamários caninos

Abstract

Canine life expectancy has increased significantly in the last decade. Consequently, there was a higher incidence of age-related diseases, such as neoplasms. For female dogs, breast neoplasms are the most common type of cancer, and approximately 50% of them are malignant. Once tumors are caused by chemical and physical changes in the cell, studies that characterize these abnormalities are essential. X-Ray Fluorescence (XRF) is one the most common technique used for determining the elemental composition of tissues. The Compton scattering technique, on the other hand, allows determining the electron density of samples, providing information about the tissue matrix. In this sense, the objective of this work was to study the variations in trace elements (Fe, Cu and Zn) concentration and electron density, in normal and neoplastic canine mammary tissues, combining XRF and Compton scattering techniques. Initially, computational simulations were carried out aiming the optimization of the experimental conditions. After the simulations, thirteen samples were analyzed at the Instituto de Física Gleb Wataghin (IFGW), using an energy dispersive X-ray fluorescence (ED-XRF) arrangement, to obtain the trace elements concentrations and the electron densities of the samples, simultaneously. Another seven samples were analyzed at the Laboratório Nacional de Luz Síncrotron (LNLS), in two separate experiments. First, the micro X-ray fluorescence (µ-XRF) technique was applied for mapping the spatial distribution of Fe, Cu and Zn around the tumors. Then, the Compton scattering measurements were performed at selected points of the samples, in order to obtain values of electron density at these points. The simulations results optimized the experimental conditions, providing a better use of the beam time for the experiments carried out at the LNLS. The results obtained in the experiments with the ED-XRF arrangement, despite the percentage fluctuations, served as the basis for an estimation of the concentration values of Cu and Zn and the sample's electron densities. The µ-XRF experiments provided maps with the spatial distributions of Fe, Cu and Zn around the tumors, which were compared to the histological slides and the electron density values found in the Compton scattering experiment. A higher concentration of Cu was observed in a benign tumor sample (simple adenoma), and increased Fe in regions close to tumors, and Zn was homogeneously distributed in most of the samples. Regarding the values of electron density, there was agreement with other works present in the literature, with higher values in tumor regions, and smaller in the areas of adipose tissue. Therefore, it is observed that the combination of XRF and Compton scattering techniques is an effective way for obtaining complementary information in studies with canine mammary tumors.