INSTITUTO DE PESQUISAS ENERGÉTICAS E NUCLEARES
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Navegação Periódicos - Artigos por Agências de fomento "Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)"

Navegação Periódicos - Artigos por Agências de fomento "Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)"

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  • IPEN-DOC 27731

    MENDES, BRUNO M.; ANTUNES, PAULA C.G. ; BRANCO, ISABELA S.L. ; NASCIMENTO, EDUARDO do; SENIWAL, BALJEET; FONSECA, TELMA C.F.; YORIYAZ, HELIO . Calculation of dose point kernel values for monoenergetic electrons and beta emitting radionuclides: intercomparison of Monte Carlo codes. Radiation Physics and Chemistry, v. 181, p. 1-8, 2021. DOI: 10.1016/j.radphyschem.2020.109327

    Abstract: Targeted radionuclide therapy (TRT) and beta-emitting seeds brachytherapy (BSBT) exploit the characteristics of energy deposited by beta-emitting radionuclides. Monte Carlo (MC) modelling of electron transport is crucial for calculations of absorbed dose for TRT and BSBT. However, computer codes capable of providing consistent results are still limited. Since experimental validations show several difficulties, the estimation of electron dose point kernel (DPK) is often used to verify the accuracy of different MC codes. In this work, we compared DPK calculations for various point, isotropic and monoenergetic electron sources and several beta-emitting radioisotopes using the codes MCNP, EGSnrc, PENELOPE and TOPAS with different simulation options. The simulations were performed using latest versions of EGSnrc and Penelope, TOPAS version 3.3.1 and MCNP version 6.1 Monte Carlo codes. In our simulations, the geometrical model consists of a point electron source placed at the center of a water sphere emitting isotropically. The water sphere was divided into 28 shells and the energy deposition was scored within these shells. The radius of the outermost shell was 1.2R0, where R0 is the continuous slowing down approximation (CSDA) range. Five monoenergetic beta sources with energies of 0.05, 0.1, 0.5, 1 and 3 MeV were studied. Six beta-emitting radionuclides were also simulated: Lu-177, Sm-153, Ho-166, Sr-89, I-131 and Y-90. Monoenergetic electron simulations showed large deviations among the codes, larger than 13% depending on the electron energy and the distance from the source. In the cases where beta spectra of radionuclides were simulated, all MC codes showed differences from EGSnrc (used as reference value - RV) less than 3% within rE90 range (radius of the sphere in which 90% of the energy of the spectrum electrons would be deposited). TOPAS showed results comparable to EGSnrc and PENELOPE. DPK values for 0.1 MeV monoenergetic electrons, calculated using MCNP6, led to differences higher than ±5% from RV despite our attempts to tune electron transport algorithms and physics parameters.

    Palavras-Chave: point kernels; computer calculations; computerized simulation; electron emission; electrons; beta particles; radionuclides; monte carlo method; therapy; brachytherapy

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  • IPEN-DOC 27202

    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

    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

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  • IPEN-DOC 27804

    SANTOS, WILLIAM S. ; NEVES, LUCIO P.; PERINI, ANA P.; SANTOS, CARLA J.; BELINATO, WALMIR; SILVA, ROGERIO M.V.; SOARES, MARIA R.; VALERIANO, CAIO C.; CALDAS, LINDA V.E. . Computational modelling of cervix radiation procedure using a virtual anthropomorphic phantom and the MCNPX code. Journal of Physics: Conference Series, v. 1826, p. 1-8, 2021. DOI: 10.1088/1742-6596/1826/1/012040

    Abstract: There is a serious, and growing concern about the increased risk of the emergence of a secondary cancer, radio-induced, associated with radiotherapy treatments. To assess the radiation doses to organs outside the target volume, in this work, several computational exposure scenarios were modelled, based on Monte Carlo simulation (MCNPX code). A Varian 2100c accelerator, and a female virtual anthropomorphic phantom were used, in a simulated treatment of cervical cancer. The determination of the dispersed dose would be important for assessing the risk in different organs or tissues. Four treatment fields were applied, varying the gantry angle. It was possible to observe that the conversion factors for equivalent dose were higher for the AP projection. For the RLAT and LLAT projections, the results were similar, fact that may be attributed to the symmetrical distributions of the organs in relation to the radiation source. The results presented in this work showed that the computational exposure scenario provides a versatile and accurate tool to estimate in a ready way the absorbed doses during a cervical treatment.

    Palavras-Chave: absorbed radiation doses; animal tissues; computerized simulation; dosimetry; monte carlo method; organs; phantoms; radiotherapy; uterus

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  • IPEN-DOC 25125

    OLIVEIRA, JUSTINE P.R. ; MELENDEZ-ORTIZ, H.I.; BUCIO, EMILIO; ALVES, PATRICIA T.; LIMA, MAYARA I.S.; GOULART, LUIZ R.; MATHOR, MONICA B. ; VARCA, GUSTAVO H.C. ; LUGAO, ADEMAR B. . Current methods applied to biomaterials – characterization approaches, safety assessment and biological international standards. Current Topics in Medicinal Chemistry, v. 18, n. 4, p. 256-274, 2018. DOI: 10.2174/1568026618666180410151518

    Abstract: Safety and biocompatibility assessment of biomaterials are themes of constant concern as advanced materials enter the market as well as products manufactured by new techniques emerge. Within this context, this review provides an up-to-date approach on current methods for the characterization and safety assessment of biomaterials and biomedical devices from a physical-chemical to a biological perspective, including a description of the alternative methods in accordance with current and established international standards.

    Palavras-Chave: biological materials; bioassay; medicine; in vitro; in vivo; compatibility; composite materials; sterilization; standardization; iso; recommendations; physical chemistry

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  • IPEN-DOC 24752

    SOARES, MARIA R. ; SANTOS, WILLIAM S.; NEVES, LUCIO P.; PERINI, ANA P. ; BATISTA, WILSON O.G.; BELINATO, WALMIR; MAIA, ANA F.; CALDAS, LINDA V.E. . Dose estimate for cone beam CT equipment protocols using Monte Carlo simulation in computational adult anthropomorphic phantoms. Radiation Physics and Chemistry, v. 155, SI, p. 252-259, 2019. DOI: 10.1016/j.radphyschem.2018.06.038

    Abstract: Cone beam computed tomography (CBCT) has become essential for dental diagnoses in the last decade. This is supported by its low cost and low doses, when compared to medical CT. Following this increase in CBCT procedures, it is necessary to ensure the image quality within low radiation doses to the patients. This is an especially difficult challenge in CBCT, given the number of equipment models (more than 50), radiographic techniques that may be employed, and technical information not available to the users by the manufacturers. The objective of this study was to estimate the cancer risk, effective and absorbed doses in tissues and organs for CBCT protocols intended for dental use. Monte Carlo (MC) simulations were used to estimate these quantities in tissues and organs with radiological importance, as those suggested by the International Commission of Radiological Protection (ICPR) report ICRP 103. Five different fields of view (FOV) were simulated to i-Cat Classic CBCT, using the MCNPX code. The virtual anthropomorphic phantoms FASH3 (Female Adult MeSH) and MASH3 (Male Adult MeSH) were also used. The effective dose estimative was in the range 75.15–142.20 μSv. The largest contribution to the effective dose was from the salivary glands (17%), thyroid (27%) and remainder tissues (28%). The results of this work showed that the effective and absorbed doses in tissues/organs vary according to the FOV, exposure parameters, and the positioning of the beam, relative to the radiosensitive organs. Furthermore, for the same exposure conditions, women can exceed the total risk of cancer by 26–34%, when compared to men.

    Palavras-Chave: computerized tomography; monte carlo method; dosimetry; phantoms; computerized simulation; irradiation; tomography

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  • IPEN-DOC 26430

    PEREIRA, MARCO A.M.; SILVEIRA, LUCAS M.; NANNINI, FELIX; NEVES, LUCIO P.; PERINI, ANA P.; SANTOS, CARLA J.; BELINATO, WALMIR; SANTOS, WILLIAM S. . Dosimetric evaluation of individuals to 238U series, 232Th series and 40K radionuclides present in Brazilian ornamental rocks using computational simulation. Ecotoxicology and Environmental Safety, v. 173, p. 401-410, 2019. DOI: 10.1016/j.ecoenv.2019.02.038

    Abstract: Granites are widely used in construction and they may be potential sources of ionizing radiation, due to the presence of radionuclides such as 40K and decay products from 238U series and 232Th series. These radionuclides occur in the minerals constituting the rocks. To evaluate the doses in humans exposed to 40K, and decay products from 238U series and 232Th series radiation, a room with dimensions of 4.0 × 5.0 × 2.8m3, with uniformly distributed radiation source on the floor of granitic rocks, was computationally modeled. Adult individuals were represented in the virtual scenario by two virtual anthropomorphic phantoms FASH3 and MASH3, incorporated simultaneously in the software MCNPX 2.7.0. The mean energy deposited on each organ and tissue of FASH3 and MASH3 phantoms was determined using the MCNPX F6 tally (MeV/g/particle), while the photon flux within the room was calculated with the MCNPX F4 tally (MeV/cm2/particle). The organs that obtained the highest conversion coefficients CC[HT] (Sv/Gy) were the red bone marrow (0.94), skin (0.90), breast (0.81) and bladder (0.73) for the FASH3; skin (0.89), gonads (0.88), breast (0.79) and bladder (0.70) for the MASH3. The simulated air absorbed dose rates varied between 23.4 (11%) and 25.8 (12%) nGy/h, and the annual dose rates were 0.10 (6%) and 0.11 (6%) mSv/year. These results presented acceptable statistical uncertainties and they are in agreement with the literature. Fluency of photons pointed to the central region of the room floor as the place of greatest exposure. The results showed that the organs closer to the radiation source had the highest deposited energy values. Based on the annual effective dose data obtained, it was possible to note that the values are within the literature. We believe that the methodology used will allow the investigation of any ornamental material that emits natural radiation.

    Palavras-Chave: rocks; granites; ionization; ionizing radiations; computerized simulation; natural radioactivity; dosimetry; monte carlo method; phantoms; radioisotopes; uranium 238; thorium 232; potassium 40; brazil

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  • IPEN-DOC 24788

    PERINI, ANA P. ; SANTOS, WILLIAM S.; NEVES, LUCIO P.; BELINATO, WALMIR; CALDAS, LINDA V.E. . Estimation of conversion coefficients for absorbed and effective doses for pediatric CT examinations in two different PET/CT scanners. Radiation Physics and Chemistry, v. 155, SI, p. 9-16, 2019. DOI: 10.1016/j.radphyschem.2018.07.009

    Abstract: Normally, during medical procedures, special attention must be given to pediatric patients when compared to adults. This is specially relevant during procedures involving ionizing radiation, as CT scans, given that children are considerably more sensitive to radiation induced stochastic effects than adults. In order to investigate the radiation doses on radiosensitive organs of pediatric patients, undergoing head, chest and abdomen CT procedures, numerical dosimetry was employed in this work. The novelty is the use of a new set of pediatric virtual anthropomorphic phantoms, coupled with Monte Carlo simulation, to determine the conversion coefficients for absorbed and effective doses. Two CT equipment were simulated, taking into account the main characteristics of those commercially available. The results were converted to conversion coefficients (mGy/100 mA) for several organs and tissues, and the highest values were obtained for the newborn phantom. This numerical approach employed a new and reliable technique for pediatric CT dosimetry.

    Palavras-Chave: patients; children; radiation doses; monte carlo method; phantoms; computerized tomography; pediatrics; simulation

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  • IPEN-DOC 27422

    SANTOS, WILLIAM S.; SOUZA, LUCAS W.G.; NEVES, LUCIO P.; PERINI, ANA P.; SANTOS, CARLA J.; BELINATO, WALMIR; CALDAS, LINDA V.E. . Evaluation of fetal, medical and occupational exposure in ERCP procedures using Monte Carlo simulation and virtual anthropomorphic phantoms. Radiation Physics and Chemistry, v. 177, p. 1-10, 2020. DOI: 10.1016/j.radphyschem.2020.109113

    Abstract: In this study, computational modeling was applied to evaluate medical and occupational exposure, to ionizing radiation, during the Endoscopic Retrograde Cholangiopancreatography (ERCP) procedure of a pregnant woman in the second gestational trimester. The fetal dose evaluation and the construction of a photon fluence map inside the procedure room were also performed. The medical staff and patient were represented by virtual anthropomorphic phantoms. These phantoms were incorporated to the radiation transport code MCNPX (version 2.7.0). The photon beam was projected on the right lateral lower section of the liver of the patient, producing a FOV of 15×15 cm2. The spectral influence was evaluated using tube voltages of 70 kVp and 80 kVp with a total filtration of 5 mmAl. The influence of the suspended shield, lead curtain and fetal shield were evaluated on the Conversion Coefficients for Equivalent Dose (CC[HT]) and Effective Dose (CC[E]) for the medical staff and patient. The removal of the lead curtain and suspended shield was considered the most critical configuration to the medical staff. In this situation, an increase up to 633% in the CC[HT]eye lens and 900% in CC[E], for the medical staff, was reached. The CC[E]Patient ranged between 0.13 mSv/Gy.cm2 (70 kVp with all protective devices) and 0.15 mSv/Gy.cm2 (80 kVp without fetal shield) and the values obtained are in agreement with the literature. The CC[HT]fetus oscillated between 2.2E-1 mSv/Gy.cm2 (70 kV with fetal shield) and 2.7E-1 mSv/Gy.cm2 (80 kV without fetal shield). The outcomes of this work are useful in the prior monitoring of the radiation doses and risks, and a reduction on these may be reached for the medical team and patient, which is a complicated arrangement in ERCP procedures.

    Palavras-Chave: biomedical radiography; digestive system; pregnancy; prenatal exposure; patients; monte carlo method; phantoms; medical personnel; nuclear medicine; conversion; computerized simulation; mathematical models; radiation doses; fetuses

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  • IPEN-DOC 27210

    SANTOS, CARLA J.; SANTOS, WILLIAM S. ; PERINI, ANA P.; VALERIANO, CAIO C.S. ; BELINATO, WALMIR; CALDAS, LINDA V.E. ; NEVES, LUCIO P.. Evaluation of polymer gels using Monte Carlo simulations. Radiation Physics and Chemistry, v. 167, p. 1-4, 2020. DOI: 10.1016/j.radphyschem.2019.03.038

    Abstract: The use of Monte Carlo simulations in dosimetry is a well established area of research, and several correction factors, for ionization chambers, were evaluated with these simulations. Some simulated values were considered even more reliable than the experimental measurements. Besides these uses with ionization chambers, Monte Carlo simulations may also be employed in the development and characterization of new dosimetric materials, as polymer gels. They are largely employed in radiotherapy dosimetry to mimic human tissue. New polymer gels were studied in order to better represent different organs or tissues, to provide more reliable results, or even to use different measurement techniques. The objective of this study was to evaluate the dosimetric properties of polymer gels, in relation to its mass-energy absorption coefficients, energy response and tissue equivalence. For this purpose the MCNPX Monte Carlo code was utilized. Three different materials, employed in radiotherapy dosimetry were evaluated in this work: MAGAS, MAGAT and AMPS. For all simulations carried out, the values were within an acceptable uncertainty and in accordance to the expected results.

    Palavras-Chave: polymers; gels; dosimetry; monte carlo method; radiotherapy; ionization chambers; depth dose distributions

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  • IPEN-DOC 24798

    SILVEIRA, LUCAS M. da; PEREIRA, MARCO A.M.; NEVES, LUCIO P. ; PERINI, ANA P. ; BELINATO, WALMIR; CALDAS, LINDA V.E. ; SANTOS, WILLIAM S.. Exposure to 137Cs deposited in soil – A Monte Carlo study. Journal of Physics: Conference Series, v. 975, n. 012050, p. 1-5, 2018. DOI: 10.1088/1742-6596/975/1/012050

    Abstract: In the event of an environmental contamination with radioactive materials, one of the most dangerous materials is 137Cs. In order to evaluate the radiation doses involved in an environmental contamination of soil, with 137Cs, we carried out a computational dosimetric study. We determined the radiation conversion coefficients (CC) for effective (E) and equivalent (H T) doses, using a male and a female anthropomorphic phantoms. These phantoms were coupled with the MCNPX (2.7.0) Monte Carlo simulation software, for three different types of soil. The highest CC[H T] values were for the gonads and skin (male) and bone marrow and skin (female). We found no difference for the different types of soil.

    Palavras-Chave: cesium 137; radiation accidents; environmental exposure; contamination; soils; monte carlo method; radiation sources; computer codes; dosimetry; radiation monitoring; radiation protection

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  • IPEN-DOC 27703

    SENIWAL, BALJEET; FREITAS, LUCAS F. ; MENDES, BRUNO M.; LUGAO, ADEMAR B. ; KATTI, KATTESH V.; FONSECA, TELMA C.F.. In silico dosimetry of low-dose rate brachytherapy using radioactive nanoparticles. Physics in Medicine and Biology, v. 66, n. 4, p. 1-13, 2021. DOI: 10.1088/1361-6560/abd671

    Abstract: Purpose. Nanoparticles (NPs) with radioactive atoms incorporated within the structure of the NP or bound to its surface, functionalized with biomolecules are reported as an alternative to low-dose-rate seed-based brachytherapy. In this study, authors report a mathematical dosimetric study on low-dose rate brachytherapy using radioactive NPs. Method. Single-cell dosimetry was performed by calculating cellular S-values for spherical cell model using Au-198, Pd-103 and Sm-153 NPs. The cell survival and tumor volume versus time curves were calculated and compared to the experimental studies on radiotherapeutic efficiency of radioactive NPs published in the literature. Finally, the radiotherapeutic efficiency of Au-198, Pd-103 and Sm-153 NPs was tested for variable: administered radioactivity, tumor volume and tumor cell type. Result. At the cellular level Sm-153 presented the highest S-value, followed by Pd-103 and Au-198. The calculated cell survival and tumor volume curves match very well with the published experimental results. It was found that Au-198 and Sm-153 can effectively treat highly aggressive, large tumor volumes with low radioactivity. Conclusion. The accurate knowledge of uptake rate, washout rate of NPs, radio-sensitivity and tumor repopulation rate is important for the calculation of cell survival curves. Self-absorption of emitted radiation and dose enhancement due to AuNPs must be considered in the calculations. Selection of radionuclide for radioactive NP must consider size of tumor, repopulation rate and radiosensitivity of tumor cells. Au-198 NPs functionalized with Mangiferin are a suitable choice for treating large, radioresistant and rapidly growing tumors.

    Palavras-Chave: nanoparticles; radioactive materials; radioactivity; brachytherapy; dose rates; low dose irradiation; dosimetry; radiotherapy; nanomaterials; neoplasms

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  • IPEN-DOC 27212

    SILVA, ROGERIO M.V.; BELINATO, WALMIR; SANTOS, WILLIAM S. ; SOUZA, LUIZA F.; PERINI, ANA P.; NEVES, LUCIO P.; SOUZA, DIVANIZIA N.. Low cost electron irradiator using 90Sr+90Y sources. Radiation Physics and Chemistry, v. 167, p. 1-8, 2020. DOI: 10.1016/j.radphyschem.2019.03.039

    Abstract: In beta therapy, β particles from 90Sr+90Y are used for the prevention and treatment of ophthalmological and dermatological diseases. For such purposes, the radiation dose is deposited by planar and concave applicators positioned on the region to be treated. Although this therapy is effective on the diseases, several complications have been reported, making these types of radioactive applicators obsolete in current clinical practice. This paper proposes a methodology to prepare and evaluate the safety of a research irradiator that re-purposes and adapts dermatologic and ophthalmic 90Sr+90Y applicators. The irradiator was constructed using low cost materials and three applicator sources. The sources are positioned at the center and the upper end of acrylic rectangular prisms. Radiochromic film was used to obtain the dose distribution on the sample holder surface. Pellets of aluminum oxide doped with carbon (Al2O3:C) were used to evaluate the reproducibility of the irradiator. The MCNPX Monte Carlo code was used for the evaluation of safety conditions. The irradiator exhibits good reproducibility of irradiation of dosimeters in pellet form and is safe to handle.

    Palavras-Chave: brachytherapy; strontium 90; yttrium 90; monte carlo method

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  • IPEN-DOC 29628

    CAIXETA, DOUGLAS C.; LIMA, CASSIO ; XU, YUN; GUEVARA-VEGA, MARCO; ESPINDOLA, FOUED S.; GOODACRE, ROYSTON; ZEZELL, DENISE M. ; SABINO-SILVA, ROBINSON. Monitoring glucose levels in urine using FTIR spectroscopy combined with univariate and multivariate statistical methods. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, v. 290, p. 1-9, 2023. DOI: 10.1016/j.saa.2022.122259

    Abstract: The development of novel platforms for non-invasive continuous glucose monitoring applied in the screening and monitoring of diabetes is crucial to improve diabetes surveillance systems. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy of urine can be an alternative as a sustainable, label-free, fast, non-invasive, and highly sensitive analysis to detect changes in urine promoted by diabetes and insulin treatment. In this study, we used ATR-FTIR to evaluate the urinary components of non-diabetic (ND), diabetic (D), and diabetic insulin-treated (D + I) rats. As expected, insulin treatment was capable to revert changes in glycemia, 24-h urine collection volume, urine creatinine, urea, and glucose excretion promoted by diabetes. Several differences in the urine spectra of ND, D, and D + I were observed, with urea, creatinine, and glucose analytes being related to these changes. Principal components analysis (PCA) scores plots allowed for the discrimination of ND and D + I from D with an accuracy of ∼ 99 %. The PCA loadings associated with PC1 confirmed the importance of urea and glucose vibrational modes for this discrimination. Univariate analysis of second derivative spectra showed a high correlation (r: 0.865, p < 0.0001) between the height of 1074 cm-1 vibrational mode with urinary glucose concentration. In order to estimate the amount of glucose present in the infrared spectra from urine, multivariate curve resolution-alternating least square (MCR-ALS) was applied and a higher predicted concentration of glucose in the urine was observed with a correlation of 78.9 % compared to urinary glucose concentration assessed using enzyme assays. In summary, ATR-FTIR combined with univariate and multivariate chemometric analyses provides an innovative, non-invasive, and sustainable approach to diabetes surveillance.

    Palavras-Chave: diabetes mellitus; fourier transform spectrometers; infrared spectra; urine; biological markers; quantitative chemical analysis; glucose

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  • IPEN-DOC 24712

    BELINATO, WALMIR; SILVA, ROGERIO M.V.; PERINI, ANA P. ; NEVES, LUCIO P.; SANTOS, CARLA J.; SOUZA, DIVANIZIA N.; SANTOS, WILLIAM S.. Monte Carlo dosimetric evaluation in PET exams for patients with different BMI and heights. Radiation Physics and Chemistry, v. 151, p. 36-41, 2018. DOI: 10.1016/j.radphyschem.2018.05.011

    Abstract: In recent years, positron emission tomography (PET), associated with multi-detector computed tomography (MDCT), has become a diagnostic technique widely disseminated to evaluate various malignant tumors and other diseases. However, during PET/CT examinations, the doses of ionizing radiation experienced by the internal organs of the patients due to 18F are unknown, and may be substantial. The aim of this study was to determine a set of S values derived from the 18F-FDG and to use them to determine the absorbed and effective doses of 8 different virtual anthropomorphic phantoms (4 of each gender). These phantoms have different Body Mass Index (BMI), to represent different anatomical characteristics of patients examined in PET. The results of the S values were calculated using the MCNPX (2.7.0) Monte Carlo code. These results were compared to the ICRP 106 reference values, obtained with mathematical anthropomorphic phantoms (MIRD model). Our results of the S values were higher than those obtained and presented at the ICRP 106, mainly due to the differences between the phantoms. The differences between the relative distances of the organs and the chemical and physical characteristics of the phantoms used in this study, in relation to mathematical model, reflected the use of a detailed set of phantoms. Therefore, the results presented in this study provide accurate and reliable data for internal dose calculations for patients undergoing PET examinations.

    Palavras-Chave: positron computed tomography; monte carlo method; positron sources; dosimetry; phantoms

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  • IPEN-DOC 24376

    SANTOS, WILLIAM S.; BELINATO, WALMIR; PERINI, ANA P. ; CALDAS, LINDA V.E. ; GALEANO, DIEGO C.; SANTOS, CARLA J.; NEVES, LUCIO P. . Occupational exposures during abdominal fluoroscopically guided interventional procedures for different patient sizes — A Monte Carlo approach. Physica Medica - European Journal of Medical Physics, v. 45, p. 35-43, 2018. DOI: 10.1016/j.ejmp.2017.11.016

    Abstract: In this study we evaluated the occupational exposures during an abdominal fluoroscopically guided interventional radiology procedure. We investigated the relation between the Body Mass Index (BMI), of the patient, and the conversion coefficient values (CC) for a set of dosimetric quantities, used to assess the exposure risks of medical radiation workers. The study was performed using a set of male and female virtual anthropomorphic phantoms, of different body weights and sizes. In addition to these phantoms, a female and a male phantom, named FASH3 and MASH3 (reference virtual anthropomorphic phantoms), were also used to represent the medical radiation workers. The CC values, obtained as a function of the dose area product, were calculated for 87 exposure scenarios. In each exposure scenario, three phantoms, implemented in the MCNPX 2.7.0 code, were simultaneously used. These phantoms were utilized to represent a patient and medical radiation workers. The results showed that increasing the BMI of the patient, adjusted for each patient protocol, the CC values for medical radiation workers decrease. It is important to note that these results were obtained with fixed exposure parameters.

    Palavras-Chave: radiology; dosimetry; phantoms; occupational exposure; monte carlo method; patients

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  • IPEN-DOC 29512

    MARCONDES, POLLYANA; ROSAS, GISELA H.; GONZALEZ, MARIA E.L.; QUEIROZ, ALVARO A.A. de ; MARQUES, PAULO S.. Poly(vinyl alcohol)/poly(glycerol) dendrimer hydrogel mediated green synthesis of silver nanoparticles. Polímeros, v. 32, n. 3, p. 1-9, 2022. DOI: 10.1590/0104-1428.20220025

    Abstract: In this paper, we report the synthesis and evaluation of a poly(vinyl alcohol)/poly(glycerol) dendrimer hydrogel incorporated with green synthesized silver nanoparticles (PVA/PGLD-AgNPs) using Cinnamomum verum extract as the reducting agent (Cz-extract). The Cz-extract was prepared using ultrasonic technique. UV-visible (UV-vis) spectra of Cz-extract confirmed the presence of cinnamaldehyde. PVA/PGLD-AgNPs films were prepared using 5, 10 and 20 mL of Cz-extract and characterized by UV-vis, Fourier transform infrared spectroscopy, Thermogravimetric analysis and X-ray diffraction (XRD). The surface plasmon resonance band in the UV-vis spectra confirmed the formation of AgNPs. XRD pattern confirmed the presence of silver, with average crystallite sizes calculated by Scherrer equal to 13.64 nm, 16.63nm and 20.27 nm for AgNPs prepared with 5 mL, 10 mL and 20 mL of Cz-extract, respectively. AgNPs release kinetic was studied by Korsmeyer– Peppas model. The antimicrobial results revealed that the PVA/PGLD-AgNPs hydrogels showed good antibacterial activity behavior against Escherichia coli.

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  • IPEN-DOC 28410

    SILVA, MATHEUS S.; TAVARES, ANA P.M.; COELHO, LUIZ F.L.; DIAS, LIGIA E.M.F. ; CHURA-CHAMBI, ROSA M. ; FONSECA, FLAVIO G. da; SALES, MARIA G.F.; FIGUEIREDO, EDUARDO C.. Rational selection of hidden epitopes for a molecularly imprinted electrochemical sensor in the recognition of heat-denatured dengue NS1 protein. Biosensors and Bioelectronics, v. 191, p. 1-8, 2021. DOI: 10.1016/j.bios.2021.113419

    Abstract: Rational selection of predicted peptides to be employed as templates in molecular imprinting was carried out for the heat-denatured non-structural protein 1 (NS1) of dengue virus (DENV). Conservation analysis among 301 sequences of Brazilian isolates of DENV and zika virus (ZIKV) NS1 was carried out by UniProtKB, and peptide selection was based on in silico data of the conservational, structural and immunogenic properties of the sequences. The selected peptide (from dengue 1 NS1) was synthesized and employed as a template in the electropolymerization of polyaminophenol-imprinted films on the surface of carbon screen-printed electrodes. Heat denaturation of the protein was carried out prior to analysis, in order to expose its internal hidden epitopes. After removal of the template, the molecularly imprinted cavities were able to rebind to the whole denatured protein as determined by electrochemical impedance spectroscopy. This label-free sensor was efficient to distinguish the NS1 of DENV from the NS1 of ZIKV. Additionally, the sensor was also selective for dengue NS1, in comparison with human serum immunoglobulin G and human serum albumin. Additionally, the device was able to detect the DENV NS1 at concentrations from 50 to 200 μg L−1 (RSD below 5.04%, r = 0.9678) in diluted human serum samples. The calculated LOD and LOQ were, respectively, 29.3 and 88.7 μg L−1 and each sensor could be used for six sequential cycles with the same performance.

    Palavras-Chave: viral diseases; viral diseases; zika virus; protein denaturation; polymers; sensors

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  • IPEN-DOC 25155

    SILVA, ANDERSON G.M. da; BATALHA, DANIEL C.; RODRIGUES, THENNER S. ; CANDIDO, EDUARDO G.; LUZ, SULUSMON C.; FREITAS, ISABEL C. de; FONSECA, FABIO C. ; OLIVEIRA, DANIELA C. de; TAYLOR, JASON G.; TORRESI, SUSANA I.C. de; CAMARGO, PEDRO H.C.; FAJARDO, HUMBERTO V.. Sub-15 nm CeO2 nanowires as an efficient nonnoble metal catalyst in the room-temperature oxidation of aniline. Catalysis Science and Technology, v. 8, n. 7, p. 1828-1839, 2018. DOI: 10.1039/c7cy02402a

    Abstract: We described herein the facile synthesis of sub-15 nm CeO2 nanowires based on a hydrothermal method without the use of any capping/stabilizing agent, in which an oriented attachment mechanism took place during the CeO2 nanowire formation. The synthesis of sub-15 nm CeO2 nanowires could be achieved on relatively large scales (∼2.6 grams of nanowires per batch), in high yields (>94%), and at low cost. To date, there are only a limited number of successful attempts towards the synthesis of CeO2 nanowires with such small diameters, and the reported protocols are typically limited to low amounts. The nanowires displayed uniform shapes and sizes, high surface areas, an increased number of oxygen defects sites, and a high proportion of Ce3+/Ce4+ surface species. These features make them promising candidates for oxidation reactions. To this end, we employed the selective oxidation of aniline as a model transformation. The sub-15 nm CeO2 nanowires catalyzed the selective synthesis of nitrosobenzene (up to 98% selectivity) from aniline at room temperature using H2O2 as the oxidant. The effect of solvent and temperature during the catalytic reaction was investigated. We found that such parameters played an important role in the control of the selectivity. The improved catalytic activities observed for the sub-15 nm nanowires could be explained by: i) the uniform morphology with a typical dimension of 11 ± 2 nm in width, which provides higher specific surface areas relative to those of conventional catalysts; ii) the significant concentration of oxygen vacancies and high proportion of Ce3+/Ce4+ species at the surface that represent highly active sites towards oxidation reactions; iii) the crystal growth along the (110) highly catalytically active crystallographic directions, and iv) the mesoporous surface which is easily accessible by liquid substrates. The results reported herein demonstrated high activities under ambient conditions, provided novel insights into selectivities, and may inspire novel metal oxide-based catalysts with desired performances.

    Palavras-Chave: nanostructures; nanowires; cerium oxides; aniline; oxidation; catalytic effects; synthesis

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  • IPEN-DOC 27869

    SANTOS, W.S.; NEVES, L.P.; PERINI, A.P.; SANTOS, C.J.; BELINATO, W.; CALDAS, L.V.E. . The influence of the lead eyewear geometry on the doses to the eye lens. Brazilian Journal of Radiation Sciences, v. 9, n. 1A, p. 1-9, 2021. DOI: 10.15392/bjrs.v9i1A.1347

    Abstract: The scattered radiation from interventional procedures is an important source of radiological risk for the medical staff. Considering all affected organs, the eye lens is among the most critical organs. As pointed out by several studies, even for low radiation doses, the appearance of cataract may occur. Considering this scenario, the radiation doses to the eye lens were determined using three different lead eyewear models commonly employed in the interventional radiology. The interventional radiologist was represented by an adult virtual anthropomorphic phantom (MASH3), coupled to the Monte Carlo code MCNP 6.1, in a typical cardiac interventional radiology procedure. The eyewear had a thickness 0.5 mmPb each, and the evaluation was carried out for four different beam angulations (PA, LAO90, LAO65 e RAO65), utilizing a tube voltage of 80 kVp, and HVL of 4 mmAl. The results pointed out that the shielding efficiency has a strong dependence on the eyewear type utilized, which may be very useful for the decision-making during the acquisition of such equipments.

    Palavras-Chave: crystalline lens; equivalent radiation doses; fluoroscopy; glass; lead; monte carlo method; occupational exposure; phantoms; radiation protection; shielding

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  • IPEN-DOC 27216

    SOARES, MARIA R. ; SANTOS, WILLIAM S. ; NEVES, LUCIO P.; PERINI, ANA P.; BATISTA, WILSON O.G.; MAIA, ANA F.; BELINATO, WALMIR; CALDAS, LINDA V.E. . The use of personal protection equipment for the absorbed doses of eye lens and thyroid gland in CBCT exams using Monte Carlo. Radiation Physics and Chemistry, v. 167, p. 1-6, 2020. DOI: 10.1016/j.radphyschem.2019.108347

    Abstract: The purpose of this study was to evaluate the absorbed dose in the thyroid and eye lens when the patient uses individual protection. For this purpose, Monte Carlo (MC) simulation was employed using five different field of view (FOV) sizes, available in the i-Cat classic CBCT equipment. To represent the patient, a male virtual anthropomorphic phantom was used. Three different models of lead eyewear and thyroid shield were evaluated, as well as the dose difference with and without the personal protection equipment. The difference in the absorbed dose in relation to the use of the lead eyewear presented a reduction of 19% for the 8 cm×6 cm FOV (diameter×height), and 73% for the 14 cm×22 cm FOV. In relation to the thyroid, only the shield that involved the whole neck contributed to the reduction of the absorbed dose by up to 72% for a 14 cm×22 cm FOV. For the thyroid shields there was a maximum increase of 59% (14 cm×6 cm FOV), consequently, increasing the effective dose for the protocol. The results showed that the lead eyewear contributed to the protection of the eye lens, but the efficiency of the thyroid shield depends on several factors, as FOV and shield model.

    Palavras-Chave: radiation protection; computerized tomography; monte carlo method; simulation; protective clothing; equipment; eyes; phantoms; neck

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A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

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A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

O gerenciamento do Repositório está a cargo da Biblioteca do IPEN. Constam neste RI, até o presente momento 20.950 itens que tanto podem ser artigos de periódicos ou de eventos nacionais e internacionais, dissertações e teses, livros, capítulo de livros e relatórios técnicos. Para participar do RI-IPEN é necessário que pelo menos um dos autores tenha vínculo acadêmico ou funcional com o Instituto. Nesta primeira etapa de funcionamento do RI, a coleta das publicações é realizada periodicamente pela equipe da Biblioteca do IPEN, extraindo os dados das bases internacionais tais como a Web of Science, Scopus, INIS, SciElo além de verificar o Currículo Lattes. O RI-IPEN apresenta também um aspecto inovador no seu funcionamento. Por meio de metadados específicos ele está vinculado ao sistema de gerenciamento das atividades do Plano Diretor anual do IPEN (SIGEPI). Com o objetivo de fornecer dados numéricos para a elaboração dos indicadores da Produção Cientifica Institucional, disponibiliza uma tabela estatística registrando em tempo real a inserção de novos itens. Foi criado um metadado que contém um número único para cada integrante da comunidade científica do IPEN. Esse metadado se transformou em um filtro que ao ser acionado apresenta todos os trabalhos de um determinado autor independente das variáveis na forma de citação do seu nome.