Martin E. Poletti

University of São Paulo, San Paulo, São Paulo, Brazil

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Publications (7)11.34 Total impact

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    Wender Geraldelli, Alessandra Tomal, Martin E. Poletti
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    ABSTRACT: In this work seven tissue-equivalent materials (Nylon, Polyacetate, Polymethylmethacrylate (PMMA), water, muscle-equivalent, bone-equivalent and adipose-equivalent) were characterized, through their attenuation (linear attenuation coefficient) and scattering (scattering profile) properties. An energy dispersive X-ray system (EDXS) was used to analyze these properties simultaneously. The EDXS consisted of a tungsten anode X-ray tube operating at 60 kVp, a goniometer, and two detectors: a Cadmium Telluride (CdTe) detector, positioned at 7 degrees with relation to the incident beam, used for detecting the energy distribution of the scattered photons, and a Silicon Drift Detector (SDD), positioned at zero degree with relation to the incident beam, used for detecting the energy distribution of the transmitted beam (with the sample) or the incident beam (without the sample). The preliminary results obtained in this work show the potential of combining the linear attenuation coefficient and the scattering profile for characterizing and choosing the most suitable tissue-equivalent materials to simulate human tissue. Our results show that adipose-equivalent, water and bone-equivalent would be adequate to simulate adipose, muscle and bone tissue respectively.
    IEEE Transactions on Nuclear Science 04/2013; 60(2):566-571. DOI:10.1109/TNS.2013.2248382 · 1.46 Impact Factor
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    ABSTRACT: The aim of this work is to investigate microscopic correlations between trace elements in breast human tissues. A synchrotron X-ray fluorescence microprobe system (μ-XRF) was used to obtain two-dimensional distribution of trace element Ca, Fe, Cu and Zn in normal (6 samples) and malignant (14 samples) breast tissues. The experiment was performed in X-ray Fluorescence beam line at Laboratório Nacional de Luz Síncrotron (LNLS), Campinas, Brazil. The white microbeam was generated with a fine conical capillary with a 20 μm output diameter. The samples were supported on a XYZ table. An optical microscope with motorized zoom was used for sample positioning and choice the area to be scanned. Automatic two-dimensional scans were programmed and performed with steps of 30 μm in each direction (x, y) on the selected area. The fluorescence signals were recorded using a Si(Li) detector, positioned at 90 degrees with respect to the incident beam, with a collection time of 10 s per point. The elemental maps obtained from each sample were overlap to observe correlation between trace elements. Qualitative results showed that the pairs of elements Ca-Zn and Fe-Cu could to be correlated in malignant breast tissues. Quantitative results, achieved by Spearman correlation tests, indicate that there is a spatial correlation between these pairs of elements (p < 0.001) suggesting the importance of these elements in metabolic processes associated with the development of the tumor.
    05/2012; DOI:10.1063/1.3703341
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    ABSTRACT: The application and better understanding of traditional and new breast tumor biomarkers and prognostic factors are increasing due to the fact that they are able to identify individuals at high risk of breast cancer, who may benefit from preventive interventions. Also, biomarkers can make possible for physicians to design an individualized treatment for each patient. Previous studies showed that trace elements (TEs) determined by X-Ray Fluorescence (XRF) techniques are found in significantly higher concentrations in neoplastic breast tissues (malignant and benign) when compared with normal tissues. The aim of this work was to evaluate the potential of TEs, determined by the use of the Energy Dispersive X-Ray Fluorescence (EDXRF) technique, as biomarkers and prognostic factors in breast cancer. By using EDXRF, we determined Ca, Fe, Cu, and Zn trace elements concentrations in 106 samples of normal and breast cancer tissues. Cut-off values for each TE were determined through Receiver Operating Characteristic (ROC) analysis from the TEs distributions. These values were used to set the positive or negative expression. This expression was subsequently correlated with clinical prognostic factors through Fisher's exact test and chi-square test. Kaplan Meier survival curves were also evaluated to assess the effect of the expression of TEs in the overall patient survival. Concentrations of TEs are higher in neoplastic tissues (malignant and benign) when compared with normal tissues. Results from ROC analysis showed that TEs can be considered a tumor biomarker because, after establishing a cut-off value, it was possible to classify different tissues as normal or neoplastic, as well as different types of cancer.The expression of TEs was found statistically correlated with age and menstrual status. The survival curves estimated by the Kaplan-Meier method showed that patients with positive expression for Cu presented a poor overall survival (p < 0.001). This study suggests that TEs expression has a great potential of application as a tumor biomarker, once it was revealed to be an effective tool to distinguish different types of breast tissues and to identify the difference between malignant and benign tumors. The expressions of all TEs were found statistically correlated with well-known prognostic factors for breast cancer. The element copper also showed statistical correlation with overall survival.
    BMC Research Notes 04/2012; 5:194. DOI:10.1186/1756-0500-5-194
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    ABSTRACT: The Backscatter Factors (BSF), Entrance-Surface Dose (ESD) and Relative Depth Dose (RDD) were assessed by Thermoluminescent Dosimetry (TLD) technique. The measurements have been made varying the geometric and spectral conditions, corresponding to the most radiographic techniques employed in conventional and computer mammographic procedures, i.e., beam qualities in the range of 0.35–0.43 mmAl, tube voltages from 25 kV to 32 kV, anode/filter combinations (Mo/Mo, Mo/Rh and Rh/Rh), different focus-image detector distances from 56 cm to 66 cm, area of irradiation (81, 157, 234 and 432 cm2) and thickness of the phantom. Results indicate that BSF values show a slight dependence on the various parameters considered, except with the variation of the focus-film distance, where found that this parameter does not have influence on the BSF. ESD values show a strong dependence on the various parameters considered, showing substantially lower values (40%) for computer mammography. RDD curves decrease nearly exponentially with the depth and depend strongly on the spectral conditions. The obtained values show a satisfactory agreement with other studies obtained through Monte Carlo simulation, ionization chambers and thermoluminescent dosimeters.
    Radiation Measurements 12/2011; 46(12):2086-2089. DOI:10.1016/j.radmeas.2011.06.019 · 1.14 Impact Factor
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    ABSTRACT: Small angle X-ray scattering (SAXS) images of normal breast tissue and benign and malignant breast tumour tissues, fixed in formalin, were measured at the momentum transfer range of 0.063 nm(-1) < or = q (= 4pisin(theta/2)/lambda) < or = 2.720 nm(-1). Four intrinsic parameters were extracted from the scattering profiles (1D SAXS image reduced) and, from the combination of these parameters, another three parameters were also created. All parameters, intrinsic and derived, were subject to discriminant analysis, and it was verified that parameters such as the area of diffuse scatter at the momentum transfer range 0.50 < or = q < or = 0.56 nm(-1), the ratio between areas of fifth-order axial and third-order lateral peaks and third-order axial spacing provide the most significant information for diagnosis (p < 0.001). Thus, in this work it was verified that by combining these three parameters it was possible to classify human breast tissues as normal, benign lesion or malignant lesion with a sensitivity of 83% and a specificity of 100%.
    The Analyst 07/2009; 134(6):1077-82. DOI:10.1039/b821434d · 3.91 Impact Factor
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    ABSTRACT: In this work total reflection X-ray fluorescence spectrometry has been employed to determine trace element concentrations in different human breast tissues (normal, normal adjacent, benign and malignant). A multivariate discriminant analysis of observed levels was performed in order to build a predictive model and perform tissue-type classifications. A total of 83 breast tissue samples were studied. Results showed the presence of Ca, Ti, Fe, Cu and Zn in all analyzed samples. All trace elements, except Ti, were found in higher concentrations in both malignant and benign tissues, when compared to normal tissues and normal adjacent tissues. In addition, the concentration of Fe was higher in malignant tissues than in benign neoplastic tissues. An opposite behavior was observed for Ca, Cu and Zn. Results have shown that discriminant analysis was able to successfully identify differences between trace element distributions from normal and malignant tissues with an overall accuracy of 80% and 65% for independent and paired breast samples respectively, and of 87% for benign and malignant tissues.
    Spectrochimica Acta Part B Atomic Spectroscopy 06/2009; DOI:10.1016/j.sab.2009.05.026 · 3.15 Impact Factor
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    ABSTRACT: An investigation was carried out to study the potential use of the angular distribution of scattered photons by human breast samples for a rapid identification of neoplasias of breast tissues. This technique has possible applications as diagnostic aid for breast cancer. In this work, a commercial powder diffractometer was used to obtain the scattering profiles from breast tissues histopathologically classified as normal breast tissues, fibroadenomas (benign breast diseases) and carcinomas (malignant breast diseases), in the interval 0.02A(-1) < x < 0.62A(-1). The experimental methods and data corrections are discussed in detail, and they included background subtraction, polarization, self-attenuation and geometric effects. The validation of the experimental procedure was achieved through an analysis of water sample. The results showed that the scattering profile is a unique impression of each type of tissue, being correlated with their microscopic morphological features. Multivariate analysis was applied to these profiles in order to verify if the information carried by these scattering profiles allow the differentiation between normal, benign and malignant breast tissues. The statistical analysis results showed that a correct identification of 75% of the analyzed samples is accomplished. The values of sensibility and specificity of this method in correctly differentiating between normal and neoplastic samples were 95.6% and 82.3%, respectively, while the values for differentiation between benign and malignant neoplasias were 78.6% and 62.5%. These initial results indicate the feasible use of commercial powder diffractometer to provide a rapid diagnostic with a high sensitivity.
    Journal of Radiation Research 08/2008; 49(5):527-32. DOI:10.1269/jrr.08027 · 1.69 Impact Factor