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[en] An important modality for the treatment of prostate cancer is teletherapy. The use of image-guided radiotherapy (IGRT) is a valuable tool in this treatment. This study retrospectively compared how repositioning the patient based on bone structure (B-ISO) and the prostate itself (P-ISO) affected the volumetric dose in the rectum, bladder, and clinical target volume (CTV). Additionally, the normal tissue complication probability (NTCP) for the rectum was computed. We evaluated 155 cone-beam computed tomography (CBCT) from 8 patients. The treatment plans used beam modulation techniques. The planning target volume (PTV) margin adopted in both scenarios was 1 cm. The organs of interest were outlined over each CBCT and then treatment plans were applied so that the absorbed dose could be computed. NTCP values were calculated for the rectum. Analyzing dose-volume metrics published by the Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC), there was no significant difference between the two repositioning strategies for the rectum and bladder. There was a slight degradation in CTV coverage for the B-ISO strategy, but still with adequate coverage. Analysis of the uniform equivalent dose (EUD) and NTCP for the rectum showed little sensitivity to the strategy used. The present study showed that the use of CBCT in radiotherapy for prostate cancer treatment did not significantly improve volumetric doses for the rectum, bladder, and CTV, as well as NTCP for the rectum. (author)

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[en] The fast increase of modern technologies in radiotherapy, for instance intensity-modulated radiation therapy (IMRT), has required extra efforts on pre-treatment verification quality assurance. Nowadays, most of the radiotherapy centers in Brazil assure the quality of a treatment plan by comparing the data obtained from the planning system with in-phantom measurements. Such verification method can become extremely time consuming when a high number of patients are treated at the radiotherapy center. This work aims at establishing, at the clinical routine of the Brazilian Instituto Nacional de Câncer (INCa) in Rio de Janeiro, Brazil, tolerance levels that can allow the validation of the IMSure software (version 3.7, Standard Imaging) as an independent monitor unit calculation for IMRT plans. A retrospective study conducted on patients’ radiotherapy plans who started treatment in the last seven months, concluded that, when using thresholds up to 4% for dose difference and 4 mm for distance-to-agreement in a gamma analysis, only 6% of the radiotherapy plans fail. It suggests a reduction of approximately 94% of the time consumed in radiotherapy plan-specific pre-treatment verification. Such results highlight, in most cases, the potential of the IMSure implementation at the clinical routine of big centers by virtue of its practicality, reliability and fast performance. (author)

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[en] Nanocrystals of BaFe₁₂O₁₉, with a small amount of the BaFe₂O₄, were obtained by means of the proteic sol-gel process together. The results demonstrated that the magnetic and crystallographic properties are dependent on the calcination temperature and the values of M_r/M_s are very close to 0.5, which is the expected value by the Stoner-Wohlfarth model. The best calcination temperature was at 900 deg. C with M _s=55.5 emu/g, H _c=4.1 kOe and crystallite size 39 nm

[en] The objective of the TBI treatment is the ablation of the bone marrow and the destruction of the circulating leukemia cells, once they are widely distributed throughout the body.Using beam parameters acquired under conventional SSD in TBI treatments may add non-negligible uncertainties in the monitor units calculation or in the beam profiles.The study,aims to commission the 6 and 10 MV photon beams,of the Varian accelerator CX model. A slab phantom and dosimetric assembly were used under TBI conditions. The accuracy of the TPS was evaluated against the experimental data. A set of data were acquired, highlighting the TPR table and methodology for calculating MU has been implemented. The TPS has presented a statistical uncertainty of ± 2.7 % compared to the experimental data for monitor unit calculation. The use of an acrylic spoiler has been shown to be clinically advantageous where, for a 6 MV beam, the entrance PDD was 75 % without a spoiler and 99.5 % with a spoiler. For a 10 MV beam, it was verified that without a spoiler, the entrance PDD was about 55 %, but with a spoiler, it was about 93 %. For medium Heterogeneous the TPS underestimated dose values by up to -3.5 % with a mean deviation of –2.9 %, for 6 MV and for 10 MV, the TPS overestimated the dose values by up to 1.1 %,with an average deviation of 1.0 % using the acrylic thorax phantom. The data obtained can be used clinically. (author)

[en] Radiation therapy is a complex treatment modality involving several technological and professional resources as well as a large number of attributions of these professionals with a high degree of interdependence. Thus there are many possibilities of failure in the treatment process that may lead to an accidental exposure. Regulatory agencies have established guidelines in order to prevent accidental exposures through security analysis planning and risk management. The System of EValuation of Risk in RAdiotherapy, also known as SEVRRA, is based on the risk matrix methodology and allows the risk assessment of radiation therapy facilities in a prescriptive way, highlighting events leading to high-risk levels. With SEVRRA it is also possible to establish an analysis of importance of the barriers proposed to avoid or mitigate such events. This work aimed to demonstrate the application of SEVRRA for the risk management of radiation therapy facilities. The risk profile was determined by identifying the highest risk level events, and the barriers of greater impact for the overall risk level. After implementing some missing barriers in the original facility profile, it was achieved a reduction from 31% to 8% in the number of events leading to high-risk level, showing the effectiveness of SEVRRA for the risk management in radiation therapy facilities. (author)