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This work is based on the adaptation of a commercial X-ray fluorescence mapping equipment to map the transmission of characteristic X-ray beams through a sample. This adaptation was made without physical adjustments to the equipment, working only on the measurement and data processing parameters. The arrangement of the equipment's components causes not only the primary beam to pass through the sample, but also the resulting characteristic X-rays, causing a double attenuation and a defect in the final image known as ghosting. In this approach, a rudimentary genetic algorithm was developed using artificial images with simulated defects. This algorithm showed the characteristics of the convolution matrix K needed to solve the problem. The results show the real possibility of using the equipment for this adapted measurement and a methodology that can be expanded to different situations.

Nondestructive assays are essentials for certain types of sample materials, and, among those, the X-ray fluorescence technique enables the determinations of stable elements, and there is an increasing effort on the development of equipment to suit the various needs. Nevertheless, a great difficulty on the analysis of unknown materials' composition is to account for self-absorption of the fluorescence photons that must be considered in the elemental concentration calculation. The correlation between the Rayleigh to Compton scattering ratio to the mass attenuation coefficient has proved to follow a single polynomial function for the first 20 elements of the periodical table with a correlation factor higher than of 0.998 for the sixth order function. The Rayleigh to Compton scattering ratios for pure elements and the 22.16 keV photons, the main energy from an X-ray tube with silver anode, were determined with the MCNP6 Monte Carlo computer code. Two scattering angles were considered. Reference samples were measured, and the calculated results were compared to the literature values of the mass attenuation coefficient for some known samples and showed to be within 20% for de 90° scattering angle. Only Lucite was slightly above 20%. Curve fit coefficients are also presented for the 7.11- and 17.40-keV photon energies.

In this work was developed a portable system of grazing exit X-ray fluorescence (geometric 90° - 0°) that can be applied in several areas science and technology. GE-XRF portable system is formed by a mini X-ray tube of low power (anode of Au) and a SiPIN detector. The reflectors used as sample support (sampler carrier) were quartz discs. The grazing exit angle was experimentally determined by measuring a cooper solution (10 μg.g-1). The accuracy of the system was checked using multielement reference solution as standard reference material. The relative errors between measured and certified values are in the range of 4 to 19%. The first results showed a background was drastically reduced at grazing exit angles, enabling trace elemental analysis. The system of GE-XRF proved to be quite stable and reproducible. This paper shows that it is possible to produce a portable system of grazing exit X-ray fluorescence compact, efficient, low-cost and easy-to-handle instrumentation using a low power X-ray tube and a SiPIN compact detector.

A well know way for best understanding of radiation scattering and radiation exposure rate during a procedure using ionizing radiation is to map exposure over the space around the source and sample. This map is done measuring exposure in points regularly spaced, it means, measurement will be placed in localization chosen by increasing a regular steps from a starting point, along the x, y and z axes or, in more efficient way, radial and angular coordinates. However, it is not always possible to maintain the accuracy of the steps throughout the entire space, or there will be regions of difficult access where the regularity of the steps will be impaired. In this work we use a high energy radiation source to simulate a common radiography setup and construct its exposure map. The arrangement of the points and the interpolation were used considering polar coordinates. Then with the same data, an interpolation using the Delaunay triangulation was made. The results show the advantages and disadvantages of each other besides the high coherence for the same data. To simulate the impossibility of regular points, the same procedures were performed in the absence of any point and compared. The results show a lower total variation when the map is calculated by triangulation. The computational and graphic treatment was performed with GNU OCTAVE software and its image processing package. The data were acquired from a bunker where a 6MeV betatron was used as a primary source. A well know way for best understanding of radiation scattering and radiation exposure rate during a procedure using ionizing radiation is to map exposure over the space around the source and sample. This map is done measuring exposure in points regularly spaced, it means, measurement will be placed in localization chosen by increasing a regular steps from a starting point, along the x, y and z axes or, in more efficient way, radial and angular coordinates. However, it is not always possible to maintain the accuracy of the steps throughout the entire space, or there will be regions of difficult access where the regularity of the steps will be impaired. In this work we use a high energy radiation source to simulate a common radiography setup and construct its exposure map. The arrangement of the points and the interpolation were used considering polar coordinates. Then with the same data, an interpolation using the Delaunay triangulation was made. The results show the advantages and disadvantages of each other besides the high coherence for the same data. To simulate the impossibility of regular points, the same procedures were performed in the absence of any point and compared. The results show a lower total variation when the map is calculated by triangulation. The computational and graphic treatment was performed with GNU OCTAVE software and its image processing package. The data were acquired from a bunker where a 6MeV betatron was used as a primary source.

A portable grazing exit X-ray fluorescence system (GE-XRF) composed of a low power X-ray tube (gold anode), a SiPIN detector, quartz reflector and an XY table plus rotary stage for positioning the reflector in grazing exit condition was developed in this work. The accuracy of the system was checked using a certified bovine liver sample (SRM 1577b, NIST). The relative errors between measured and certified values ranged from 2 to 22%, except P (39%) and S (26%). The absolute detection limits obtained with the portable system were in the range of 4–300 ng (15 ≤ Z ≤ 30). The portable GE-XRF system developed does not favor the detection of light elements since absorption effects were more critical (sample-to-detector distance ∼ 35 mm). Besides that, it was operated under room temperature and atmospheric pressure, 20 °C and 1.0 atm, respectively. The quantitative results of a multielement reference sample were compared with the results of a GI-XRF system. Both techniques were compatible and presented good accuracy with reference values. The portable GE-XRF system developed in this work was efficient, showing that it is possible to produce a grazing exit X-ray fluorescence system using a low power X-ray tube, a Si-PIN detector and quartz reflector.

The arrival of the human being in the islands caused a gradual alteration of the plant cover. Initially, changes started slowly, because the aboriginal population was relatively scarce and lacked metal tools for massive felling. But changes in the vegetation accelerated after the Castilian conquest, which brought a major population increase, better tools, a greater demand for land and wood, and new large livestock farm animals with their intensive plant consumption.

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFμCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), in order to determine the elemental distribution in prostate samples aiming at establishing a correlation between the concentration of some elements and the characteristics and pathology of the tissues. The CT images were reconstructed using a filtered-back projection algorithm and the XRFμCT images were reconstructed using a filtered-back projection algorithm with absorption corrections.

ACOLEP-MD (Architecture to COntrol LEarning Processes with Mobile Devices) is an architecture to support monitoring of learning processes and to allow the teacher to spent more time with pupils with more difficulties. This architecture provides a mobile device to be used by the teacher and a set of applications to manage data from students and teacher's devices. Due to Spanish government initiative of providing each of pupils with a laptop, our proposal is intended to profit as much as possible from this equipment.

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The main of this work is to determine the elemental distribution map in reference samples and breast tissue samples in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high precision goniometer and translation stages that allow rotating as well as translating it perpendicularly to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90deg to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam direction. The CT images were reconstructed using a filtered-back projection algorithm and the XRFCT were reconstructed using a filtered-back projection algorithm with absorption corrections.

The main goal of this work is two-fold: (1) to compare three different excitation conditions in x-ray fluorescence microtomography (XRFCT) in the analysis of reference samples, and (2) to determine the elemental distribution map for breast tissue samples, in order to verify concentrations of certain elements correlated with characteristics and pathology, using x-ray transmission microtomography (CT). The experiments were performed at the X-Ray Fluorescence Facility (D09B-XRF) of the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. In this work, a multilayer monochromator with photon energies near 12 keV, a monochromatic beam at 9.8 keV using a Si (111) crystal, and the white beam were used for elements excitation of elements inside the sample. The sample was placed on a high-precision goniometer and translation stages, which allowed for rotation as well as translation perpendicular to the beam. Fluorescence photons were collected by means of an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter, placed behind the sample, in the direction of the incoming beam. Transmission CT images were reconstructed using a filtered back-projection algorithm, and XRFCT images were reconstructed using a filtered back-projection algorithm with absorption correction. Copyright © 2009 John Wiley & Sons, Ltd.

The objective of this study was to characterize the bone structures of the femoral head and the cortical and trabecular regions, using two-dimensional images produced by x-ray microfluorescence, which supplies information about the superficial distribution of minerals. The measurements were performed in the standard geometry with 45 incidence, and excitation with a white beam and an optical capillary with 20 µm diameter collimation in the x-ray fluorescence (XRF) beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). The results show that both the concentration and the distribution of the minerals vary significantly among the groups, mostly in relation to the element calcium, depending on the location and bone site. Copyright © 2007 John Wiley & Sons, Ltd.

Transmission microtomography (μCT) and X-ray fluorescence microtomography (XRFμCT) are complementary and noninvasive techniques used for sample characterization. μCT provide information on the attenuation coefficients, while XRFμCT can provide the distribution of all elements in a sample. XRFμCT is a noninvasive technique, based on the detection of X-ray fluorescence emitted by the elements in the sample, and it is used to complement other techniques for sample characterization. The experiments were performed at the X-Ray Fluorescence (XRF) beamline of the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. A monochromatic beam of 9.8 keV was used for excitation of the elements within samples and the fluorescence photons were detected by an HPGe detector. The incident beam was monitored by an ionization chamber and a fast scintillator detector was used to detect the transmitted radiation. In this work, several intestine and breast tissue samples were investigated in order to verify the concentration of some elements correlated with the characteristics and pathology of each tissue observed by transmission μCT. All XRFμCT were reconstructed using a filtered back-projection algorithm. In those samples the elements Zn, Cu, and Fe were observed.

An X-ray Transmission Microtomography (CT) system combined with an X-ray Fluorescence Microtomography (XRFCT) system was implemented in the Brazilian Synchrotron Light Source (LNLS), Campinas, Brazil. The main aim of this work is to determine the elemental and absorption distribution map in breast tissue samples. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Source (LNLS), Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The fluorescence photons were acquired with an energy dispersive HPGe detector (CANBERRA Industries Inc.) placed at 90 ∘ to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter (CYBERSTAR Oxford Danfysik) placed behind the sample in the beam direction. All the tomographic images were reconstructed using a filtered-back projection algorithm.

The X-ray fluorescence microtomography (XRFCT) is a non-destructive technique to complement other techniques used for samples characterization. The common techniques provide only information on the attenuation coefficients (transmission microtomography) or electronic density (Compton microtomography) and no information on the distribution of the elements inside of the sample can be obtained in these cases. XRFCT is based on the detection of fluorescence photons emitted by the elements in the sample. As the energy of photons of fluorescence has a particular value for each element, it is possible to obtain the distribution of all the elements in a sample, since that a minimum of fluorescence signal is detected. The experiments were performed at the X-ray fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Source (LNLS), Campinas, Brazil. A monochromatic beam and a white beam was used for the excitation of the elements and the fluorescence photons have been detected by a HPGe detector, placed at 90° to the incident beam. The beam was monitored by an ionization chamber and a fast scintillator detector was used to detect the transmitted radiation. In order to study the performance of the system, some reference samples made of polyethylene filled with standard solutions were analyzed, and some tissues of human breast (normal tissue, benign tumor and malignant tumor) have been analyzed in order to verify the efficiency of the system in determination of the elemental distribution in these kinds of samples. All the tomographic images were reconstructed using a filtered-back projection algorithm. In the breast tissue samples, the elements of higher concentration were Zn, Cu and Fe.

This work reports the feasibility of a non-destructive synchrotron radiation X-ray transmission imaging technique development at Brazilian synchrotron light source. The quality control image parameters (spatial and density resolution and noise) are given and microtomograms presented. Microtomograms of biomedical samples are presented. The tomography system was mounted into the XRF beamline that uses a high-intensity white beam with 12 keV effective energy, and maximum width and height equals to 11 and 1 mm, respectively. The detector used to collect the data was a 512-pixel Hamamatsu linear array with width of 50 μm (36 μm of sensitivity length) and cooled by a Peltier junction, causing the temperature falling down to 15°C. The samples were placed over a computer controlled table with 0.5° angular resolution and turned around the center covering 360°. To reconstruct the sample a parallel beam filtered back-projection algorithm was used.

An X-ray Transmission Microtomography (CT) system combined with an X-ray Fluorescence Microtomography (XRFμCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The main objective of this work is to determine the elemental distribution in biological samples (breast, prostate and lung samples) in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high precision goniometer and translation stages that allow its rotation as well as translation perpendicular to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam direction. The CT images were reconstructed using a filtered back-projection algorithm and the XRFμCT were reconstructed using a filtered back-projection algorithm with absorption corrections. The 3D images were reconstructed using the 3D-DOCTOR software.

Prostate cancer is the most frequently diagnosed type of cancer in men and the second leading cause of their cancer death in many countries. Human tumor cells cultured in three dimensions display increased pro-angiogenic capacities and resistance to interferons, chemotherapeutic agents or irradiation, as compared with cells cultured in two dimensional monolayers. In this study, we investigated Zn distribution in prostate cancer spheroids (DU145) and analyzed the differences in the response to Zinc (0-150 μM) treatment using X-ray microfluorescence with Synchrotron Radiation (SRμXRF). The measurements were performed in standard geometry of 45° incidence, exciting with a white beam and using an optical capillary with 20 μm diameter collimation in the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). The results showed non-uniform distribution of Zn in all the spheroids analyzed. Zn treatment showed a decrease in Zn intensity with the increase of its concentration in DU145 spheroids. The differential response to zinc of DU145 cell spheroids suggests that zinc may have an important role in prostate cancer.

Iron, copper, and zinc are key micronutrients that play an important role in the immune response to Mycobacterium tuberculosis. The present study aimed to evaluate the association between serum levels of those micronutrients, inflammatory markers, and the smear and culture conversion of M. tuberculosis during 60 days of tuberculosis treatment. Seventy-five male patients with pulmonary tuberculosis (mean age, 40.0 ± 10.7 years) were evaluated at baseline and again at 30 and 60 days of tuberculosis treatment. Serum levels of iron, copper, zinc, albumin, globulin, C-reactive protein, and hemoglobin, and smear and cultures for M. tuberculosis in sputum samples were analyzed. Compared to healthy subjects, at baseline, patients with PTB had lower serum iron levels, higher copper levels and copper/zinc ratio, and similar zinc levels. During the tuberculosis treatment, no significant changes in the serum levels of iron, zinc, and copper/zinc were observed. Lower serum copper levels were associated with bacteriological conversion in tuberculosis treatment (tuberculosis-negative) at 30 days but not at 60 days (tuberculosis-positive). C-reactive protein levels and the C-reactive protein/albumin ratio were lower in tuberculosis-negative patients than in tuberculosis-positive patients at 30 and 60 days after treatment. Albumin and hemoglobin levels and the albumin/globulin ratio in patients with pulmonary tuberculosis increased during the study period, regardless of the bacteriological results. High serum globulin levels did not change among pulmonary tuberculosis patients during the study. Serum copper levels and the C-reactive protein/albumin ratio may be important parameters to evaluate the persistence of non-conversion after 60 days of tuberculosis treatment, and they may serve as predictors for relapse after successful treatment.

Radiation scatter leads to error in measurement of a projection that limits the image quality. The present work focuses on reconstruction error due to scattering in various types of soils and analysis was used to examine the spatial properties of scattered radiation in pencil beam geometry. EGS4 has been used (Electron–Gamma Shower), a general purpose Monte Carlo simulation package for coupled transport of electrons and photons in an arbitrary geometry. Scatter is measured in terms of the scatter-to-primary ratio (S/P). For a cylindrical geometry, the distribution of S/P was calculated for several thicknesses of each soil type, the intend being to determine the significance of detected scattered radiation in tomographic image. Two different photon energies were used: 60 keV and 662 keV. The dependence of S/P on soil diameter, chemical composition, bulk density and energy photon is presented. r 2001 Elsevier Science Ltd. All rights reserved.

Many studies defend the use of New Technologies in classrooms. It has been substantially proven that computer operation can be learnt at an early age, and that the use of new technologies can improve a child’s learning process. However, the main problem for the teacher continues to be that he/she cannot pay attention to all children at the same time. Sometimes it is necessary to decide which child must be first attended to. It is in this context that we believe our system has the ability to greatly help teachers: we have developed a learning process control system that allows teachers to determine which students have problems, how many times a child has failed, which activities they are working on and other such useful information, in order to decide how to distribute his/her time. Furthermore, bearing in mind the attention required by kindergarten students, we propose the provision of mobile devices (PDA - Personal Digital Assistant) for teachers, permitting free movement in the classroom and allowing the teacher to continue to help children while information about other students is being received. Therefore if a new problem arises the teacher is immediately notified and can act accordingly.

The abnormal accumulation or deficiency of trace elements may theoretically impair the formation of bone and contribute to osteoporosis. In this context, the knowledge of major and trace elements is very important in order to clarify many issues regarding diseases of the bone, such as osteoporosis, that remain unresolved. Several kinds of imaging techniques can be useful to access morphology and the minerals present in osteoporotic bones. In this work, synchrotron radiation X-ray microfluorescence was used as an X-ray imaging technique to investigate bone structures. Therefore, this research aims to improve the knowledge about some aspects of bone quality. The measurements were carried out at the Brazilian Synchrotron Laboratory Light Laboratory, in Brazil. A white beam with an energy range of 4-23 keV, a 45 degrees /45 degrees geometry and a capillary optics were used. It was demonstrated that bone quality can and must be evaluated not only by considering the architecture of bones but also by taking into account the concentration and the distribution of minerals. Our results showed that the elemental distributions in bone zones on a micron scale were very helpful to understand functions in those structures.

In this work, two X-ray techniques used were 3D microcomputed tomography (micro-CT) and X-ray microfluorescence (micro-XRF) in order to investigate the internal structure of the bone samples. Those two techniques work together, e.g. as a complement to each other, to characterize bones structure and composition. Initially, the specimens were used to do the scan procedure in the microcomputer tomography system and the second step consists of doing the X-ray microfluorescence analysis. The results show that both techniques are powerful methods for analyzing, inspecting and characterizing bone samples: they are alternative procedures for examining bone structures and compositions and they are complementary.

The X-ray fluorescence microtomography (XR-FCT) is a non-destructive technique, based on the detection of X-ray fluorescence emitted by the elements in the sample, and it is used to complement other techniques for sample characterization. In this work human breast tissues samples have been analyzed in order to verify the efficiency of the system in the determination of the elemental distribution in these kind of samples. The experiments were performed at the X-ray fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Source (LNLS), Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used for the excitation of the elements and the fluorescence photons have been detected by a HPGe detector, placed at 90deg to the incident beam. The beam was monitored by an ionization chamber and a fast scintillator detector was used to detect the transmitted radiation. In one projection, samples were positioned in steps of 200 mum (actual beam size) perpendicularly to the beam direction covering the whole transversal section of the sample proof. Each single value in a projection is obtained by measuring the fluorescent radiation emitted by all pixels along the beam. The object is then rotated, and another projection is measured. Projections are obtained in steps of 3deg until the object has completed 180deg. The selected measuring for each scanned point was evaluated separately for each sample. All the tomographies have been reconstructed using a filtered-back projection algorithm. In the breast tissue samples, the elements of higher concentration were Zn, Cu and Fe.

The success of matrix acidification depends on the adequate distribution of acids over all the extension to be treated, known as divergence. Acid stimulation of oil and gas reservoirs, with a view to increasing well productivity, has been applied since the late 19th century. Initially applied in carbonate reservoirs, the technique was extended to more complex mineralogies, over a number of years, like unconsolidated sandstones. However, we can say that acid stimulation of wells is the exception rather than the rule. This probably stems from the complex, heterogeneous nature of formation mineral and unpredictability of their response to conventional oilfield acid formulations. With inappropriate acid designs, or poor job procedures, even the best candidate wells can be damaged, sometimes irreversibly. If the interval presents layers with different permeabilities, the acid will tend to penetrate only in more permeable layers, leaving the zones of smaller permeability without treatment. If the reservoir consists in a heterogeneous medium, the treatment could not be uniformly distributed and the lack of good method for acid distribution might result that a great part of the damage will not be removed due to the acid that is only able to penetrate in portion with smaller damage of the interval. In the matrix treatment of extensive intervals (> 10m) it is indispensable the utilization of one method to produce divergence, which can be obtained from particulate materials or more recently with foams, resins, viscoelastics fluids or polymers modified of relatively permeability. The divergent agents can be equally distributed to all extension of the treatment or can be placed in divergent spacers intercalated into the treatment which total volume is subdivided in stages. The aim of this study is to obtain diverting agents that make possible remote operations. In this study, the X-ray computerized tomography (CT) scan was used to evaluate in real-time the performance of diverting agent during rock-fluid interactions. A special aluminum cell (physical simulator) was designed to simulate as closely as possible the same conditions found in "situ" oil wells. For example, pressure, temperature, fluid pressure injection, permeability, porosity and oil and water saturations of studied reservoir. A sequence of tests that was performed in the unconsolidated sandstones that simulate deepwater fields found in Campos Basin, in different formations, confirmed the efficiency of the system, effectiveness and the diverting effect for a lot of zones with different permeabilities.

In radiology, the X-ray film is placed between two screens. The development of radiological intensifying screens has reduced the radiation dose in patients about a factor of 10 in the last decades. The sensitivity of X-ray films is enlarged due to the fluorescent light from these screens. In addition, the primary radiation can be scattered coherently (Rayleigh scattering) and incoherently (Compton scattering) which will degrade the image resolution. Scattered radiation produced in Gd2O2Si:Tb intensifying screens was simulated by using a Monte Carlo radiation transport code - the EGS4 (Electron - Gamma Shower), which is a general purpose package for Monte Carlo simulation of the coupled transport of electrons and photons. The magnitude of scattered radiation striking the film is typically quantified using the scatter to primary radiation (SPR). The angular distribution of the intensity of the scattered radiation (sum of both the scattering effects) was simulated, showing that the ratio of scatter- to-primary radiation incident on the X-ray film is about 8.39% and 7.73% for the front and back screen, respectively, over the range from 0 to (pi) rad.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Nowadays, there is an increasing interest in user co-operation and the different ways of accomplishing user tasks. Users share a common scenario sinudtarreously. In such systems, we must take into account technological aspects as well as human factors. Characteristics involved with users (such as usability and performance) as well as the social and contextual organisation Hurst be studied. By doing so, an abstract model, regarding design and implementation details, allow us to contemplate the efficiency of these properties.

A system for surface inspection based on the physical principle of Compton scattering of gamma-rays is presented here. Our system consists of a collimated 137 Cs source and a NaI(Tl) detector. An experimental search was carried out to determine the best layout of the array. A set of aluminium blocks with different surface conditions has been tested, and imperfections up to 1.6 mm were detected.