[en] The 3D-CT and stereological techniques are used concomitantly. The quantitative stereology yields measurements that reflects areas, volumes, lengths, rates and frequencies of the test body. Two others quantification, connectivity and anisotropy, can be used as well to complete the analysis. In this paper, it is presented the application of 3D-CT and the stereological quantification to analyze a special kind of test body: ceramic filters which have an internal structure similar to cancellous bone. The stereology is adapted to work with the 3D nature of the tomographic data. It is presented too the results of connectivity and anisotropy

[en] This work outlines the quality assurance program for the activity measurements of the most used radionuclides at Brazilian Nuclear Medicine Services (NMS). The program aims to guarantee that the patient is given the correct prescribed amount of activity in diagnostic or therapeutic applications. This accurate administration depends upon proper use and calibration of the activity meters by the NMS. Underestimation of administered activity in diagnostic practices could delay correct diagnosis disturbing the value of the investigation. On the other hand, the overestimation would be worse, mainly in therapeutic applications, because an unnecessarily high absorbed dose would be delivered to the patient. The preliminary results of intercomparison for ¹³¹I and ^99mTc showed that many activity meters used at NMS's present problems giving results up to 41% greater than the reference values determined at the National Metrology Laboratory for Ionizing Radiation (LNMRI) which is recognized as the Brazilian authorized metrology laboratory for ionizing radiation. These results have demonstrated that the NMS should improve the accuracy of the activity measurements of the radionuclides administered to the patients and establish the traceability to the national standards of measurements. These standards are based on a pressurized well-type ionization chamber installed at LNMRI and calibrated with reference sources standardized by absolute methods. The protocol of the intercomparison and recommendations made in order to minimize errors in measuring procedures are described and results are discussed

[en] A solution of ¹⁶⁹Yb was absolutely standardized by the 4π(EC,X)-γ coincidence counting method and the result was used to obtain direct measurements of gamma-ray emission probabilities with a coaxial HPGe detector. The empirical relation proposed by (Vano, F., Gonzalez, L., Gaeta R., Gonzalez, J.A., 1975. An empirical function which relates the slope of the Ge efficiency curves and the active volume Nucl. Instr. Meth. 123, 573) was tested using the gamma spectral response above 200 keV. The half-life of ¹⁶⁹Yb was also measured with a 4πγ ionization chamber

[en] A gaseous position sensitive detector originally designed to operate with X-rays has been modified for using in thermal neutron tomographic systems. This modification included the replacing of the standard argon-methane mixture by ³He-enriched helium. Due to its low-density, helium should be submitted to a relatively high pressure in order to increase its stopping-power for the products emerging from the ³He(n,p)³H nuclear reaction. High pressure however, creates tightness problems. To mitigate this difficulty some heavy gases have been mixed to helium, reducing thus the range of the particles. In this work, three gases have been studied: pure ³He-enriched helium, and its mixture with argon-methane and with propane. For each case the parameters governing the performance of a detector coupled to a tomographic system, such as spatial resolution, linearity and response homogeneity have been determined. Besides that, the modulation transfer function and the distance resolution curve for a tomographic system incorporating a detector filled with those three different gases have been measured. The best spatial resolution - around 800 μm - has been obtained with a helium-propane mixture. This kind of detector is intended to equip thermal neutron tomographic systems, to perform non-destructive assay, exploiting thus the capability of this particle to pass through heavy materials where a X-ray tomography would not work properly. For an equivalent resolution, a tomographic system using a detector of this kind would require a much shorter acquiring time with regard to the first generation systems, since a sample translation is no longer necessary

[en] ²⁰¹Tl is frequently used in radiopharmaceutical applications, and therefore the gamma-ray emission probabilities and half-life have been re-determined by means of gamma-ray spectroscopy. While the activity was calibrated using the sum-peak coincidence method, the half-life was obtained by the reference source method based on simultaneous counting of a reference source and the sample. Both the measurement techniques and assignment of uncertainties are presented and discussed, and the resulting data are shown to be in good agreement with previously published studies

[en] Characterization of fatigue on asphaltic mixture in laboratory test had been done by phenomenological equations. In these equations, fatigue life, N_f (number of cycles until the rupture of the specimen (is related with σ_t (maximum strength) for controlled stress test. This work shows the development and the results of an experimental procedure using the computerized tomography technique to assessing of these theoretical parameters which govern the cracks propagation through asphaltic mixture. (author). 9 refs., 7 figs

[en] This work applies the computed tomography technique to the study of asphaltic mixtures. After analysing Marshall stability and indirect tensile strength tests. This techniques was used for NDT structural evaluations of test and field specimens. By analysing the CT images of the asphaltic mixtures it is possible to compare quality and physical conditions of test and field specimen. The results of these investigations presented in the paper ca be used to increase the asphaltic mixtures quality by improving design and procedure of manufacturing. (author). 7 refs., 10 figs

[en] In this work the Compton Backscattering Technique is used to detect the superficial defects on bodies with tubular shape. The study was performed using system with a Cesium-137 source with activity of 74 x 10¹⁰ Bq (2 Ci) and a 2 inches Na I(Tl) scintillator detector placed in such a way that it was possible to obtain scattering angles around the 180 degrees. In the first part of the work we use the differential spectrum of scattered radiation to analyse the thickness of know samples. With the calibration obtained was possible determine the thickness with precision of 4% for samples within the calibration limits and 6% for values beyond this limits.In the second part we use the calibration to analyse surface defects. It was possible detect corrosion with 2.0 mm in a 7.73 mm diameter tube wall 6.3 mm thick for corrosion in the first tube wall with the tube positioned 5.0 mm apart of the detector. (author). 6 refs., 12 figs., 1 tab

[en] In the last decades a new type of detector which is based on photostimulable luminescence was developed. There are currently many kinds of image plates (IPs) available on the market, originating from different manufacturers. Each kind of plate distinguishes itself from the others by its peculiar physical structure and composition, two factors which have a direct influence upon the quality of the digital radiographic images obtained through them. For this study, several kinds of IPs were tested in order to determine in which way such influence takes place. For this purpose, each kind of IP has been characterized and correlated to its response in the final image. The aim of this work was to evaluated procedures for employing Computed Radiography (CR) to welding inspections in laboratory conditions using the Simple Wall Simple Image Technique (SWSI). CR tests were performed in steel welded joins of thickness 5.33, 12.70 and 25.40 mm. It was used an X-Ray equipment as radiation source. The image quality parameters Basic Spatial Resolution (BSR), Normalized Signal-to-Noise Ratio (SNRN), contrast and detectability were evaluated. In order to determine in which way the IPs' properties are correlated to its response in the final image, the thickness of the sensitive layer was determined and the grain size and the elemental composition of this layer were evaluated. Based on the results drawn from this study, it is possible to conclude that the physical characteristics of IPs are essential for determining the quality of the digital radiography images acquired with them. Regarding the grain size and the thickness of the IPs' sensitive layers, we could determine that the dimensions of such parameters were smaller on the plates presenting higher BSR, SNRN and contrast. However, the image plates which produced images with the highest resolution have also proven to be the least sensitive ones. All these parameters have a direct influence in the detectability of the defects found in the welded joints, were it was possible to observe that for images obtained with plates with small grain size and thinner sensitive layer, the defects could be better visualized, including small cracks and pores.

[en] This work presents the characterization of the developed detectors using small bismuth germanate (BGO) crystals coupled to silicon PIN photodiodes of rectangular geometry and different areas. Particularly, the applicability of this combination for γ-ray energy (662 keV) detection has been investigated, with the desire to develop a useful scintillator-photodiode detector suitable for non destructive tests applications in substitution of the conventional ones. With these developed detectors we attained 5700-6800 electron-hole pairs created per MeV of energy loss in the BGO crystal, depending on the photodiode and light collection optimization. (author). 7 refs., 4 figs