Abstract: At the Calibration Laboratory (LCI) of the IPEN/CNEN, studies are in development on the establishment of a standard composed by the beta radiation sources for the dosimetry and calibration for personal monitoring in Brazil. For this purpose is used the Böhm extrapolation chamber (PTW model 23392). This chamber was already characterized at LCI in 90Sr/90Y beams using two different entrance windows: one of aluminized Mylar and another of PET (polyethylene terephthalate) known as Hostaphan. In this work, this extrapolation chamber was characterized in 85Kr and 147Pm beams. All tests were carried out with the reference 90Sr /90Y source, for comparison purposes. The Monte Carlo code MCNP5 code was used to obtain an extrapolation chamber and the BSS2 system sources computational model, based on the determination of the absorbed dose rate. Saturation curves, ion collection efficiency, ion recombination, polarity effect, stability of response, null depth, linearity of response, variation of response as a function of source-detector distance, extrapolation curves, correction factors and absorbed dose rates were obtained. The difference between the experimental absorbed dose rates and those obtained using the Monte Carlo model, compared to those from the calibration certificates, was less than 1.9% for the 108 histories for each BSS2 system source. All results of the performed tests are within the limits of the international recommendations. The results for the 90Sr/90Y source were in good agreement with previous works performed at LCI. These results are suitable for the establishment of a standard instrument for the dosimetry and calibration of beta radiation sources and detectors in the LCI/IPEN. This standard will allow the calibration of detectors in beta radiation beams in dosimetry services in Brazil.

Palavras-Chave: extrapolation chambers; radiation doses; beta sources; monte carlo method; calibration; calibration standards; laboratories

POLO, IVON O.; SANTOS, WILLIAM S.; CALDAS, LINDA V.E. Characterization of an extrapolation chamber in beta radiation beams and Monte Carlo modelling. Radiation Physics and Chemistry, v. 171, p. 1-9, 2020. DOI: 10.1016/j.radphyschem.2020.108746. Disponível em: http://repositorio.ipen.br/handle/123456789/31423. Acesso em: $DATA.

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Abstract: There is a great demand for phantoms by many areas of knowledge to be used for teaching or daily work. However, commercial phantoms are expensive and hard to obtain, especially in countries going through development. As an alternative, 3D printing can be the way to produce less expensive and reliable 3D phantoms. The goal of this study is to evaluate 14 available commercial filaments, in order to find if and how they can be used in 3D printed phantoms in computed tomography. Each material was printed as a 2 cm edge cube with rectilinear pattern and 60, 80 and 100% infill. The 80% infill of five other patterns were also printed and compared. Each 100% infill cube was weighted and had its density calculated. After that, the cubes were scanned in a Philips CT Brilliance 6 with 120 kVp, 200 mA, 2 mm slices and standard reconstruction. At the center of each cube, a ~120 mm2 region of interest was set to measure the mean Hounsfield Unit (HU) and its standard deviation. The software Origin was used to plot HU results for rectilinear pattern, determine linear trends with its R2 and compare achieved values with HU tissue range from literature. To confirm the response of HU values of selected tested materials in CT imaging as a function of percentage infill, a phantom prototype of a finger was 3D printed. The HU of the tested materials ranged from −516.2 ± 7.3 to 329.8 ± 18.9. All human tissues could be mimicked making use of these materials, except cortical bone above ~350 HU and tooth parts. The most promising filament was PLA + Cu, due to the multiple infill configuration that allows the resulting HU range to represent from adipose and skin tissue to marrow bone.

Palavras-Chave: 3d printing; phantoms; fabrication; filaments; radiology; computerized tomography

SAVI, MATHEUS; ANDRADE, MARCO A.B.; POTIENS, MARIA P.A. Commercial filament testing for use in 3D printed phantoms. Radiation Physics and Chemistry, v. 174, p. 1-7, 2020. DOI: 10.1016/j.radphyschem.2020.108906. Disponível em: http://repositorio.ipen.br/handle/123456789/31424. Acesso em: $DATA.

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Abstract: Phantom objects have as main requirement to have the effective atomic number and linear attenuation coefficient approximately equal to the human tissue to be simulated. The present work aims to characterize samples of materials radiologically equivalent to water for dose studies in patients in the diagnostic energy range. Water was chosen as reference material representing human tissue, which is composed mostly of it. A set of samples was formulated and submitted to radiation transmission tests in four different values of tension applied to an Xray tube. Mass densities of the samples were evaluated using the Arquimedes method. The samples were identified as A, B, C and D. By transmission curves, it was possible to estimate the samples transmission factors corresponding to the water transmission factor for different thicknesses. Moreover, the thicknesses of samples equivalent to water thickness for different values of transmission factor were also evaluated. All the samples densities were bigger than the density of water. For the same thickness of water and the samples, the radiation transmission of the developed materials are in better agreement for thicknesses of 10mm and 30 mm. The lowest percentage difference between the water transmission and the transmission of any of the samples obtained was approximately 0.6% for the sample A in the thickness of 30mm under voltage of 60 kV. The correspondence between the transmission factors and the thicknesses showed that the compounds studied in this work are potential materials to develop phantoms that simulate the transmission properties of human tissue.

Palavras-Chave: tissue-equivalent materials; radiation protection; transmission; experimental data; comparative evaluations; data transmission; phantoms

NASCIMENTO, BRUNA C.; FRIMAIO, AUDREW; BARRIO, RAMON M.M.; SIRICO, ANA C.A.; COSTA, PAULO R. Comparative analysis of the transmission properties of tissue equivalent materials. Radiation Physics and Chemistry, v. 167, p. 1-7, 2020. DOI: 10.1016/j.radphyschem.2019.04.050. Disponível em: http://repositorio.ipen.br/handle/123456789/31425. Acesso em: $DATA.

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Abstract: The commissioning and quality assurance The Total Skin Electron Beam (TSEB) irradiation treatment is based on the AAPM's report 23, which describes the six-dual-field (Standford) technique, and the Hospital Israelita Albert Einstein (HIAE) follows this recommended guidance. The Dosimetric Materials Laboratory of the Instituto de Pesquisas Energéticas e Nucleares (IPEN-LMD) has tradition in research related to thermoluminescent materials and its clinical applications. Thus, aiming to apply the LiF:Mg,Ti, the most common TLD material, and CaSO4:Dy + Teflon produced at IPEN as easy-to-use alternatives to electron beams dosimetry and its parameters applied to TSEB, this paper reports a comparative study of the TL responses of both materials to dose evaluation in TSEB treatments. The TL response of both materials was evaluated in several TSEB parameter tests such as clinical field homogeneity, Monitor Units (MU) calculation, absorbed doses over the reference line and throughout the surface of the skin in a treatment simulation using AldersonRando anthropomorphic phantom. Results show that the field homogeneity measurements remained within ± 8% acceptance limit from AAPM Report 23, little to no energy dependency over the range of 4 o 9 MeV electron beams and, for clinical measurements and MU calculations, both TLDs present compatible results and can be used as alternative tools in TSEB dosimetry.

Palavras-Chave: lithium fluorides; thermoluminescence; thermoluminescent dosimetry; skin; calcium sulfates; dysprosium; dosimetry

ALMEIDA, S.B.; VILLANI, D.; SAKURABA, R.K.; REZENDE, A.C.P.; CAMPOS, L.L. Comparative study of the TL response of LiF:Mg,Ti and CaSO4:Dy in the clinical electron beams dosimetry applied to total skin irradiation (TSEB) treatments. Radiation Physics and Chemistry, v. 155, p. 121-126, 2019. SI, DOI: 10.1016/j.radphyschem.2018.05.025. Disponível em: http://repositorio.ipen.br/handle/123456789/29260. Acesso em: $DATA.

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Abstract: Radiolytic synthesis and phytochemical-driven gold reduction for the generation of nanoparticles are successful examples of Green Chemistry applied for nanomaterials. The present work compares these two green approaches focusing on hydrodynamic size, stability over time, optical properties and toxicity in NIH 3T3 (ATCC® CRL- 1658™) cells and Danio rerio (Zebra Fish). The radiolytic synthesis was performed by mixing 1 mM NaAuCl4; polyvinyl pyrrolidone 0.5%, AgNO3 6×10−5 M, propan-2-ol 0.2 M and acetone 0.06 M, followed by irradiation at 15 kGy (5 kGy h−1, 60Co source). The EGCG-functionalized nanoparticles were synthesized by mixing 1.6 mM of Au with 0.8 mM of EGCG in phosphate buffer (10 mM) for 2 h. Both methods yield the formation of gold nanoparticles featuring plasmon resonance bands at 520–530 nm, polydispersity above 0.3 was relevant only for the radiolytic protocol. Regarding stability over time, after 30 days, the nanoparticles synthesized radiolytically presented no relevant size changes, while some aggregation was observed for the EGCG-particles. The same nanoparticles demonstrated a lack of stability in high ionic strength medium. Slight toxicity was observed for the EGCG-nanoparticles in Danio rerio, with an IC50 calculated as 40.49%, while no IC50 was established within the concentration range of radiolysis-AuNPs used in this study. In conclusion, both green methods generated nanoparticles with good control of size and optical properties, especially via reduction by EGCG. However, the stability and toxicity results were found to be more promising for the radiolytically synthesized gold nanoparticles.

Palavras-Chave: gold; nanoparticles; synthesis; chemistry; ecology; polyphenols; fishes

FREITAS, LUCAS F. de; CRUZ, CASSIA P.C. da; CAVALCANTE, ADRIANA K.; BATISTA, JORGE G. dos S.; VARCA, GUSTAVO H.C.; MATHOR, MONICA B.; LUGAO, ADEMAR B. Comparison between gold nanoparticles synthesized by radiolysis and by EGCG-driven gold reduction. Radiation Physics and Chemistry, v. 174, p. 1-9, 2020. DOI: 10.1016/j.radphyschem.2020.108959. Disponível em: http://repositorio.ipen.br/handle/123456789/31427. Acesso em: $DATA.

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Abstract: The craniofacial structure is three-dimensional, and for a better visualization of these structures, Computed Tomography is often employed for diagnoses, even though being a high-cost procedure, leading to increased exposure to ionizing radiation. As a consequence, studies in dosimetry are necessary, since several radiosensitive structures are located in the head and neck, such as thyroid, crystalline and salivary glands. There is an overall consensus regarding the exposure of pediatric patients to ionizing radiation, with recommendations being that the procedures must occur with the shortest exposure time as possible, and it is only prescribed when they are effectively necessary. During the procedures, radiation effects are difficult to be measured. The use of either TL or OSL dosimeters can create artifacts within the images, and the positioning of a large number of dosimeters, necessary for the correct dose evaluation, is not feasible when it comes to a pediatric patient. Therefore pediatric virtual anthropomorphic phantoms and Monte Carlo simulations were used in this work. The absorbed and effective doses were determined during an i-CAT procedure, with 5 different fields of view, utilizing 5- and 10- year-old male virtual anthropomorphic phantoms. The results pointed out that the eye lens, salivary glands and thyroid received the highest doses. Besides, the effective dose values increase with the increasing of the FOV size, and the 5-year-old male virtual anthropomorphic phantom presented the highest effective dose values.

Palavras-Chave: ionizing radiations; pediatrics; dosimetry; monte carlo method; phantoms; computerized simulation

NEVES, LUCIO P.; FRANCO, ADRIANE B.; FRANÇA, MONIQUE; SOARES, MARIA R.; BELINATO, WALMIR; SANTOS, WILLIAM S.; CALDAS, LINDA V.E.; PERINI, ANA P. Computational dosimetry in a pediatric i-CAT procedure using virtual anthropomorphic phantoms. Radiation Physics and Chemistry, v. 167, p. 1-5, 2020. DOI: 10.1016/j.radphyschem.2019.03.040. Disponível em: http://repositorio.ipen.br/handle/123456789/31428. Acesso em: $DATA.

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Abstract: In recent years, an upsurge in demand for neutron calibrations has been experienced in Brazil and several other countries in Latin America, mainly due to the increase in oil prospection and extraction procedures. The only laboratory for calibration of neutron detectors in Brazil is located at the Institute for Radioprotection and Dosimetry (IRD/CNEN), Rio de Janeiro. This laboratory is the national standard dosimetry laboratory in Brazil. With the increase in the demand for the calibration of neutron detectors, the need for more calibration services became evident. In this context, the Calibration Laboratory of IPEN/CNEN, São Paulo, which already offers calibration services of radiation detectors with standard X, gamma, beta and alpha beams, recently projected a new calibration laboratory for neutron detectors. One of the main problems in this kind of calibration laboratory is related to the knowledge of scattered radiation. In order to evaluate it, simulations were performed without the presence of the structural elements and with the complete room. Thirteen measurement points were evaluated at various distances. As part of the characterization process of the radiation fields of the new Neutron Calibration Laboratory, this work presents results on the influence of the radiation scattered by the structural components of the room: walls, doors, ceiling and floor, in different calibration positions, on the detector response. Therefore, the neutron radiation attenuation and the scattering parameters were determined at different source-detector distances, through computational simulation, using the MCNP5 Monte Carlo code.

Palavras-Chave: radiation scattering analysis; neutron detectors; calibration; monte carlo method; neutron fluence; calibration standards

ALVARENGA, TALLYSON S.; POLO, IVON O.; PEREIRA, WALSAN W.; SILVA, FELIPE S.; FONSECA, EVALDO S.; CALDAS, LINDA V.E. Contribution of the scattered radiation on the neutron beam fluence at the calibration laboratory of IPEN. Radiation Physics and Chemistry, v. 167, p. 1-5, 2020. DOI: 10.1016/j.radphyschem.2019.03.023. Disponível em: http://repositorio.ipen.br/handle/123456789/31429. Acesso em: $DATA.

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