We demonstrated in previous investigations that the internal structure of paintings can be visualized with conventional radiography in transmission mode when paintings have the proper stratigraphy. Unfortunately, there are many paintings that do not result in useful images. This problem can be solved by using radiography in emission mode. With this technique, the painting is irradiated with high energetic X-rays originating from an X-ray tube operating at 100 keV - 320 keV while inside the painting low energetic signals such as photoelectrons or characteristic photons are being generated. These signals escape from the top 10 µm of the painting and are able to illuminate the imaging plate. However, this technique has also some disadvantages. One of them is that it is not able to visualize underlying paintings. In this study, we explored the possibility to enhance the information depth by increasing the energy of the photon source from 100 keV up to 1.3325 MeV (i.e., 60 Co source). At the same time, we also studied how the contrast between pigments is generated in emission mode. For this, we used mathematical simulation of particle transport in matter to understand the relation between input particle (particle type such as photon, electron or positron and the energy of the particle), the material being irradiated (element from which it is composed, thickness and density) and the output signal (generated particle types and energy). Finally, we will show that it is possible to image paintings using a 192 Ir and even a 60 Co source.

Energy‐dispersive X‐ray fluorescence (XRF) is an attractive analytical method to determine the level of air pollution by heavy metals. The concentration of the filter in ng/cm2 is obtained by direct comparison of the net characteristic line intensity of an element with that of a thin film standard. As the sampled area on the filter and the area of the standard are larger than the area analysed by the instrument, the distribution of the elements on the surface of both samples and standards have to be sufficiently uniform. If this is not the case, biased concentration estimates are obtained. Two scanning macro‐XRF setups with a beam diameter of ~0.5 mm were used to investigate the distribution of elements in (1) commercially available (Micromatter) standards, (2) in‐house quartz filter standards obtained with an aerosol generator and (3) particulate matter (PM10) collected on quartz filters by a Leckel SEQ 47/50 sampler. The uniformity of the Micromatter standards was better than 2%. At least some in‐house standards showed a concave distribution with less material at the edges. The maximum bias introduced by this is less than 5%. Because of the limited sensitivity of scanning XRF compared with conventional XRF, the distribution of only a few common elements like Ca and Fe could be determined reliably in aerosol filters. The distribution of some heavy elements could only be measured in filters sampled in polluted regions. In general, the loading of particulate matter over the filters was uniform. Copyright © 2017 John Wiley & Sons, Ltd.

The radiation damage, in terms of atom displacements, induced by gamma irradiation in LYSO and LuYAP crystals is presented. 44Sc, 22Na and 48V are used as gamma sources for this study. The energy of gammas from the electron–positron annihilation processes (511keV) is also included in the study. The atom displacements distributions inside each material are calculated following the Monte Carlo assisted Classical Method introduced by the authors. This procedure also allows to study the atom displacements in-depth distributions inside each crystal. The atom displacements damage in LYSO crystals is found to be higher than in LuYAP crystals, mainly provoked by the displacements of silicon and oxygen atoms. But the difference between atom displacements produced in LYSO and LuYAP decreases when more energetic sources are used. On the other hand, the correlation between the atom displacements and energy deposition in-depth distributions is excellent. The atom displacements to energy deposition ratio is found to increases with more energetic photon sources. LYSO crystals are then more liable to the atom displacements damage than LuYAP crystals.

Four x-ray techniques: computed radiography, emission radiography, energy-resolved radiography and imaging x-ray fluorescence were compared using four mock-up panel paintings. The paintings have different stratigraphy and pigments and are representative for different historical periods. One of the paintings has a hidden underlying painting. The type of pigments used mainly influences the information obtained by both the emission and absorption measurements; high-Z white pigment and high-Z color pigments giving the best contrast. Each of the techniques revealed interesting aspects of the paintings, but none of them could reveal the hidden painting to a satisfactory level. Due to the statistical quality of the spectral data, x-ray fluorescence gives elemental images with high contrast. The radiographic images are better to reveal the internal structure. Imaging x-ray fluorescence and energy-resolved radiography measurements can be done simultaneously, and the combination has the highest potential for the study of complex multilayer paintings. Copyright (c) 2015 John Wiley & Sons, Ltd.

Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10-90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5-50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20-70%) with respect to the previous studies. (C) 2014 Elsevier B.V. All rights reserved.

Nowadays the electronic structure calculations allow the study of complex systems determining the hyperfine parameters measured at a probe atom, including the presence of crystalline defects. The hyperfine electric parameters have been measured by Mössbauer spectroscopy in silicon materials implanted with Mn57→Fe57 ions, observing four main contributions to the spectra. Nevertheless, some ambiguities still remain in the 57Fe Mössbauer spectra interpretation in this case, regarding the damage configurations and its evolution with annealing. In the present work several implantation environments are evaluated and the 57Fe hyperfine parameters are calculated. The observed correlation among the studied local environments and the experimental observations is presented, and a tentative microscopic description of the behavior and thermal evolution of the characteristic defects local environments of the probe atoms concerning the location of vacancies and interstitial Si in the neighborhood of 57Fe ions in substitutional and interstitial sites is proposed.

Magnetic state of 57Fe implanted and doped ZnO samples have been reported and studied by Mössbauer spectroscopy at different temperatures. The Mössbauer spectra mainly showed four doublets and three sextets, but some ambiguous identification remains regarding the probe site location and influence of defects in the hyperfine and magnetic parameters. In the present work some possible implantation configurations are suggested and evaluated using Monte Carlo simulation and electronic structure calculations within the density functional theory. Various implantation environments were proposed and studied considering the presence of defects. The obtained 57Fe hyperfine parameters show a good agreement with the reported experimental values for some of these configurations. The possibility of Fe pair formation, as well as a Zn site vacancy stabilization between the second and third neighborhood of the implantation site, is supported.

A first-principles study of the electric field gradient (EFG) calculated for ideal and 111In(111Cd) implanted ZnO samples is reported in the present work. The study was made for ZnO ideal hexagonal structures and supercells were introduced in order to consider the possible implantation environments. The calculation was done using the “WIEN2k” code within the density functional theory, the exchange and correlation effects were determined by the GGA approximation. Three possible 111In(111Cd) implantation configurations were studied, one substitutional incorporation at cation site and two interstitials. The obtained EFG values for the ideal structure and the substitutional site are in good agreement with the experimental reports measured by perturbed angular correlation (PAC) and high precision nuclear magnetic resonance (NMR). Thus, the ascription of substitutional incorporation of 111In(111Cd) probe atom at the ZnO cation site after annealing was confirmed.

The radiation damage created in silicon materials by Mn-57 -> Fe-57 ion implantation has been studied and characterized by Mossbauer spectroscopy showing four main lines, assigned to: substitutional, interstitial and damaged configuration sites of the implanted ions. Nevertheless, the Mossbauer spectrum of Fe-57 in this materials remains with some ambiguous identification regarding the implantation configurations before and after annealing, specially the damaged configurations and its evolution. In the present work some possible implantation configurations are suggested and evaluated using a multiscale approach by Monte Carlo ion transport and electronic structure calculations within DFT. The proposed implantation environments were evaluated in terms of stability and the Fe-57 hyperfine parameters were calculated to establish the connections with the experimental observations. Good agreement was found between the experimental and the calculated hyperfine parameters for some configurations; suggesting which ones could be the implantation environments before and after sample annealing.

We present the energy resolution and imaging performance of a digital X-ray imaging system based on a 512-strip silicon strip detector (SSD) working in the edge-on configuration. The SSDs tested in the system are 300μm thick with 1 or 2-cm-long strips and 100μm pitch. To ensure a very small dead area of the SSD working in edge-on configuration, the detector is cut perpendicular to the strips at a distance of only 20μm from the end of the strips. The 512-strip silicon detector is read out by eight 64-channel integrated circuits called DEDIX [Grybos et al., IEEE Trans. Nucl. Sci. NS-54 (2007) 1207]. The DEDIX IC operates in a single photon counting mode with two independent amplitude discriminators per channel. The readout electronic channel connected to a detector with effective input capacitance of about 2pF has an average equivalent noise charge (ENC) of about 163el. rms and is able to count 1Mcps of average rate of input pulses. The system consisting of 512 channels has an excellent channel-to-channel uniformity—the effective threshold spread calculated to the charge-sensitive amplifier inputs is 12el. rms (at one sigma level). With this system a few test images of a phantom have been taken in the 10–30keV energy range.

Descriptores: Detector semiconductor; radiograf´ ia digital; imagen medica; rayos X; caracterizacion; maniqu´ i; biopsia. The present work synthesizes the experimental results obtained in the characterization of 64 microstrips crystalline silicon detector designed for experiments in high energies physics, with the objective of studying its possible application in advanced medical radiography, specifi- cally in digital mammography and angiography. The research includes the acquisition of two-dimensional radiography of a mammography phantom using the scanning method, and its comparison with similar images simulated mathematically for different X rays sources. The paper also shows the experimental radiography of two biological samples taken from biopsies of mammas, where it is possible to identify the presence of possible pathological lesions. The results reached in this work point positively toward the effective possibility of satisfactorily introducing those advanced detectors in medical digital imaging applications.

The present work synthesizes the experimental results obtained in the characterization of 64 microstrips crystalline silicon detector designed for experiments in high energies physics, with the objective of studying its possible application in advanced medical radiography, specifically in digital mammography and angiography. The research includes the acquisition of two-dimensional radiography of a mammography phantom using the scanning method, and its comparison with similar images simulated mathematically for different X rays sources. The paper also shows the experimental radiography of two biological samples taken from biopsies of mammas, where it is possible to identify the presence of possible pathological lesions. The results reached in this work point positively toward the effective possibility of satisfactorily introducing those advanced detectors in medical digital imaging applications.

In the present work the extended Monte Carlo assisted Classical Method (MCCM) is presented. The method consists on a calculation procedure for the determination of the displacements per atom (dpa) distribution in solid materials, which allows studying the gamma irradiation damage in different materials. The same one is based on the electrons elastic scattering classic theories and makes use of the Monte Carlo simulation of physical processes involved in the radiation interactions with substance. Recently, the contribution from positrons to dpa distributions has been also included. This method has been applied to different materials: metals (iron), semiconductors (Si and CZT) and high temperature superconductors like YBCO. Among other things, this procedure has allowed to study the dpa cross sections and the in-depth dpa distributions in a wide range of incident gamma energies. Also in compound materials, the contribution from each atomic species is possible to be evaluated.

The digital radiography gradually displaces its filmic predecessor and in this behavior the development of new radiation detectors with better properties plays an essential role. A microstrips crystalline silicon detector designed for High Energies Physics researches is analyzed as detector for digital mammography. With this objective the detector was electrically and spectrometrically characterized. Also, using phantoms of fibrous structures and microcalcifications, were carried out experiments in order to obtain digital radiographic images. The obtained results were satisfactory and reveal the potentiality of this detector to be introduced in the digital mammography.

The Monte Carlo simulation of small animal conventional positron emission tomography (PET) is an important tool for geometry parameters optimization, image reconstruction algorithm tests, performance of different radioisotopic sources and some others. The present work deals with the Monte Carlo study of a small cylindrical PET system in the framework of the GEANT4 code. Two different accepted ring width values and spherical sources of 18F and 44Sc isotopes were considered. Then, the improvement of the detection efficiency and spatial resolution was analyzed in all the cases.

The present paper synthesizes the results obtained in the evaluation of a 64 microstrips crystalline silicon detector coupled to RX64 ASIC, designed for high‐energy physics experiments, as a useful X‐ray detector in advanced medical radiography, specifically in digital mammography. Research includes the acquisition of two‐dimensional radiography of a mammography phantom using the scanning method, and the comparison of experimental profile with mathematically simulated one. The paper also shows the experimental images of three biological samples taken from breast biopsies, where it is possible to identify the presence of possible pathological tissues.

We present the development of a 512-channel module for high counting rate digital X-ray imaging systems. The module consists of 512 silicon micro-strips equipped with 8 64channel readout ASICs called DEDIX. The detectors of 300 pin thickness have strips with 100 micron pitch and strip length of I or 2 cm. Detectors were designed with the possibility of choosing the cutting edge distance from the active area in the range from 60 uri down to 20 [un. To obtain good detection efficiency at the relevant energies (10-50 keV) the module works in edge-on configuration: strips are oriented parallel to the incoming X-ray beam. The DEDIX ASIC has a binary readout architecture. Each channel is built of a charge sensitive amplifier (CSA) with pole-zero cancellation circuit, a shaper, two independent discriminators and two independent 20-bit counters. Internal correction DAC implemented in each channel independently ensures a low spread of discriminator effective threshold. This module has been characterized for noise and matching performance having in mind possible future applications like dual energy mammography and angiography. An equivalent noise charge is below 210 el rms for a I cm long strip detector and below 250 el. rnis for 2 cm long strip detector with 100 pni pitch. The spread of discriminator effective threshold for 512 channels is 16 el. rms, while the high counting rate performance has been demonstrated by the measurement up to I MHz average rate of input signals per single channel.

The effect of the energy dispersion of a quasi‐monochromatic x‐ray beam on the performance of a dual‐energy x‐ray imaging system is studied by means of Monte Carlo simulations using MCNPX ( Monte Carlo N‐Particle eXtended) version 2.6.0. In particular, the case of subtraction imaging at the iodine ‐edge, suitable for angiographic imaging application, is investigated. The average energies of the two beams bracketing the iodine ‐edge are set to the values of 31.2 and 35.6 keV corresponding to the ones obtained with a compact source based on a conventional x‐ray tube and a mosaic crystal monochromator. The energy dispersion of the two beams is varied between 0 and 10 keV of full width at half‐maximum (FWHM). The signal and signal‐to‐noise ratio produced in the simulated images by iodine‐filled cavities (simulating patient vessels) drilled in a PMMA phantom are studied as a function of the x‐ray energy dispersion. The obtained results show that, for the considered energy separation of 4.4 keV, no dramatic deterioration of the image quality is observed with increasing x‐ray energy dispersion up to a FWHM of about 2.35 keV. The case of different beam energies is also investigated by means of fast simulations of the phantom absorption.

Este articulo describe el procedimiento seguido en la obtencion de imagenes digitales con fines medicos utilizando detectores de microcintas de silicio. Se muestra el proceso de calibracion y obtencion de los parametros de optimizacion del circuito de lectura RX64. Se describe el proceso de analisis de las imagenes obtenidas a partir de un fantoma dinamico de angiografia y su correspondiente simulacion en el codigo de transporte de particulas MCNP-4C. 0.15cm