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[en] Carbon-11 labeled dl-threo-methylphenidate (methyl-2-phenyl-2-(2-piperidyl)acetate, Ritalin), a psychostimulant drug widely used to treat attention deficit hyperactivity disorder, was prepared in two steps: O-methylation of the N-protected dl-threo-ritalinic acid derivative with [¹¹C]methyl iodide followed by deprotection. The same strategy was applied for the preparation of C-11 labeled individual enantiomers of threo-methylphenidate from N-protected d-threo-l-threo-ritalinic acid. The subsequent C18 sep-pak and reverse-phase HPLC purification resulted in ca. 40% radiochemical yield with a total synthesis time of 40 minutes and an average specific activity of 1.5 Ci/μmole (at EOB). (author)

[en] Recently the IAEA fundamental objective and associated fundamental safety principles incorporate the requirement for a graded approach, particularly in respect to the assessment of safety and the assessment of radiation risks. The Brazilian National Nuclear Authority is responsible for the licensing and regulation of the radiotherapy facilities in Brazil. So far, the method applied for organizing the RF inspection program have been time elapsed since the last inspection. This method is difficult to be applied when there are low human resources, and in a very heterogeneous country, as Brazil. This work suggests a new methodology to be used by the Brazilian Nuclear Authority to organize the inspection program, using the graded approach criteria. This new methodology can optimize the number of inspections realizes each year, and focus specially on the facilities that present higher risks.

[en] Introduction: A shielding design suitable for rooms with accelerators is an important security measure for the protection of IOEs and members of the general public. NCRP 151 lays out the general considerations for the calculation of shielding in standard radiotherapy rooms, although it is noted that many shield designs differ from this standard room, such as mazeless rooms. Labyrinth-free rooms have been more commonly used, as they require less space to be built. As they are recent constructions there is no international norm or recommendation for those type of rooms. Therefore, the objective of this study is to evaluate the absorbed dose relative to neutrons in a room model without labyrinth, and to verify if these doses are within the limits established by CNEN. Methods: To evaluate the absorbed doses due to neutrons, we used the computer simulation with the code MCNPX. Accelerators were simulated with energies of 10 MeV, 15 MeV and 18 MeV. Results and Discussion: To date the results have been obtained for accelerators of 10 MeV. The results were compared with analytical calculations. The equivalent dose obtained for neutrons is within the permitted limit, according to the CNEN regulation. The results for the other bundles are still being calculated. Conclusions: This study shows the equivalent doses due to neutrons in non-labyrinthine, non-labyrinth radiotherapy rooms established in NCRP 151. This study is necessary to establish guidelines for the construction of this type of room, so that the individual dose limits of IOEs and the public are respected

[en] Purpose: Use the methodology developed by the National Research Council Canada (NRC), for Fricke Dosimetry, to determine the G-value used at Ir-192 energies. Methods: In this study the Radiology Science Laboratory of Rio de Janeiro State University (LCR),based the G-value determination on the NRC method, using polyethylene bags. Briefly, this method consists of interpolating the G-values calculated for Co-60 and 250 kV x-rays for the average energy of Ir-192 (380 keV). As the Co-60 G-value is well described at literature, and associated with low uncertainties, it wasn’t measured in this present study. The G-values for 150 kV (Effective energy of 68 keV), 250 kV (Effective energy of 132 keV)and 300 kV(Effective energy of 159 keV)were calculated using the air kerma given by a calibrated ion chamber, and making it equivalent to the absorbed to the Fricke solution, using a Monte Carlo calculated factor for this conversion. Instead of interpolations, as described by the NRC, we displayed the G-values points in a graph, and used the line equation to determine the G- value for Ir-192 (380 keV). Results: The measured G-values were 1.436 ± 0.002 µmol/J for 150 kV, 1.472 ± 0.002 µmol/J for 250 kV, 1.497 ± 0.003 µmol/J for 300 kV. The used G-value for Co-60 (1.25 MeV) was 1,613 µmol/J. The R-square of the fitted regression line among those G-value points was 0.991. Using the line equation, the calculate G-value for 380 KeV was 1.542 µmol/J. Conclusion: The Result found for Ir-192 G-value is 3,1% different (lower) from the NRC value. But it agrees with previous literature results, using different methodologies to calculate this parameter. We will continue this experiment measuring the G-value for Co-60 in order to compare with the NRC method and better understand the reasons for the found differences

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[en] Purpose: To compare absorbed dose to water standards for HDR brachytherapy dosimetry developed by the Radiological Science Laboratory of Rio de Janeiro State University (LCR) and the National Research Council, Canada (NRC). Methods: The two institutions have separately developed absorbed dose standards based on the Fricke dosimetry system. There are important differences between the two standards, including: preparation and read-out of the Fricke solution, irradiation geometry of the Fricke holder in relation to the Ir-192 source, and determination of the G-value to be used at Ir-192 energies. All measurements for both standards were made directly at the NRC laboratory (i.e., no transfer instrument was used) using a single Ir-192 source (microSelectron v2). In addition, the NRC group has established a self-consistent method to determine the G-value for Ir-192, based on an interpolation between G-values obtained at Co-60 and 250kVp X-rays, and this measurement was repeated using the LCR Fricke solution to investigate possible systematic uncertainties. Results: G-values for Co-60 and 250 kVp x-rays, obtained using the LCR Fricke system, agreed with the NRC values within 0.5 % and 1 % respectively, indicating that the general assumption of universal G-values is appropriate in this case. The standard uncertainty in the determination of G for Ir-192 is estimated to be 0.6 %. For the comparison of absorbed dose measurements at the reference point for Ir-192 (1 cm depth in water, perpendicular to the seed long-axis), the ratio Dw(NRC)/Dw(LCR) was found to be 1.011 with a combined standard uncertainty of 1.7 %, k=1. Conclusion: The agreement in the absorbed dose to water values for the LCR and NRC systems is very encouraging. Combined with the lower uncertainty in this approach compared to the present air-kerma approach, these results reaffirm the use of Fricke solution as a potential primary standard for HDR Ir-192 brachytherapy

[en] Brazilian National Nuclear Energy Commission (CNEN) makes a constant effort to keep updated with international standards and national needs to strength the radiological protection status around the country. Guidelines related to radiation treatment facilities have been revised in the last five years in order to take in consideration the most relevant aspects of the growing technology as well as to mitigate the accidents or incidents observed in the radiation therapy practice. Hence, clinical dosimeters have gained special importance as significant items in Brazilian regulation. In present work we discuss the importance of inspections from the point of view of equipment dosimetry and instruments quality control. The dosimeter sets based on thimble, well ionization, small sized and ultra small sized ion chambers need periodic calibration, and this calibration becomes a fundamental task in order to guarantee the dose prescribed-delivered to patients. Thus Brazilian guidelines enforces the need of at least two sets of clinical dosimeters with thimble chambers calibrated and one set of electrometer with well ionization chamber for hdr equipment. We call attention to the fact that inspections are a very valuable tool in order to enforce the application of guidelines around the country both by enlightening the weaker aspects of facilities concerning radiological protection and by stating in loco that reasons which lead the regulatory body to enforce such guidelines items. (author)

[en] Breast cancer (BC) survival is increased by the diagnosis of earlier-stage disease and treatments improve, however, the side effects of cancer treatments, such as cardiotoxicity, remain clinically important. Radiotherapy for breast cancer often involves some incidental exposure of the heart to ionizing radiation. Women with breast cancer who are treated with adjuvant radiation have a decreased risk of local recurrence but an increased risk of mortality from coronary artery disease (CAD). The possible reason to occurrence of CAD after radiotherapy is the unfavourable remodelling of the coronary artery due the radiation injury. Although the effects of cardiotoxicity induced by BC treatment are well known, its precise mechanisms are not completely elucidated. Losartan is an angiotensin II type 1 receptor (AT1) antagonist widely used for the treatment of hypertension as well as other cardiovascular diseases. Previous studies showed the efficacy of losartan to correct the altered structure and endothelial dysfunction of resistance arteries from patients with essential hypertension, and also prevent the progression of coronary atherosclerosis in patients with significant atherosclerotic disease. The present study aims to clarify how the radiotherapy for breast cancer affects the coronary artery and to determine if losartan can be used to minimize the side effects of the irradiation in this artery. Determination of the distribution and chemical state of elemental constituents within biological systems at sub-cellular level down to trace level concentrations is of growing importance for gaining new insights about the highly complex functions of elements within the tissue or cells. CARNAÚBA (Coherent X-Ray Nanoprobe Beamline) is the tender-to-hard X-ray nanoprobe under construction at the new Brazilian synchrotron light source SIRIUS. The beamline provides two separated experimental stations, one with sub-micrometer resolution and another with nanometer resolution, to cover various analysis techniques, including X-ray fluorescence (XRF). The all achromatic CARNAÚBA optics will covers continuously the energy range from 2 to 15 keV. With this energy range, it will be possible to analyze K-lines of light elements, like phosphorus and sulfur, and also heavier elements, like calcium and zinc. The use of CARNAÚBA beamline will provide both submicrometer spatial resolution and elemental mapping of important elements in coronary artery of hypertensive rats allowing analyze the tissue in a cellular level. (author)