| Περίληψη: | Breast cancer is the most common cause of cancer deaths worldwide. Early detection is important in order the patients to have right treatment and better recovery. Masses and microcalcifications (μCs) are important indicators of breast cancer since they are early stage signs. Only the appearance of μCs in a mammogram leads to the detection of significant percentage of breast cancers. Microcalcifications of the breast are described as calcium deposits within the breast tissue and are divided into Type I and Type II. Type I μCs are composed of calcium oxalate, and are associated with benign lesions of the breast. Type II μCs are composed of calcium phosphate, mainly hydroxyapatite, and are associated with malignant breast conditions. Calcifications composed of calcium carbonate are also associated with benign lesions of the breast. Up to date there is no non-invasive method to distinguish between benign and malignant μCs. When μCs, or other suspicious signs, are present in a mammogram, biopsy follows. A non-invasive method that could have the ability to characterize μCs is of interest. Such a method will contribute to discriminate between benign and malignant μCs avoiding painful procedures (biopsy). In the present thesis, the potential of characterization of μCs using the dual energy X-ray technique is examined. Calcium oxalate, calcium carbonate and hydroxyapatite μCs were considered in this study, and their effective Calcium/Phosphorus (Ca/P) mass ratio was calculated through analytical modeling. A monoenergetic study was conducted in order to select the optimum energy pair based on the minimization of the Coefficient of Variation (CV) of the effective Ca/P mass ratio. In the polyenergetic study followed both single and double exposure techniques were examined. Numerous filter materials and thicknesses, selected according to their K-absorption edges, were applied to the X-ray spectra in order to obtain mean energies similar to those indicated by the monoenergetic study. The effective Ca/P mass ratio was calculated for all μCs types and thicknesses using the optimized irradiation conditions. The experimental evaluation was performed using different X-ray tubes and energy integrating and energy dispersive (imaging) detectors for the single and double exposure techniques, respectively. Based on the results of the experimental procedure, statistical significant difference was observed between the different types of minerals when μCs thicknesses were 300 μm or higher.
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