RESUMO
PET cyclotrons are widely used for producing medical diagnostic radionuclides. The main radionuclide produced in these facilities is the 18F, which is obtained from the [18O (p,n)18F] reaction when 18O-enriched water is bombarded with the proton beams. This work aimed to estimate the radiation source term from the bombardment of an 18O-enriched water target with protons of 16.5 MeV to determine the radiation neutron field around the accelerator.
Assuntos
Ciclotrons , Prótons , Isótopos de Oxigênio , Método de Monte Carlo , ÁguaRESUMO
As CT exams impart high doses to patients in comparison to other radiologist techniques, reliable dosimetry is required. In this work, dosimetry in CT beams was carried out in terms of air kerma index in air or in a phantom measured by a pencil ionization chamber, thermoluminescent (TL) detectors and radiochromic film. Calibration results showed the low energy dependence of all three dosimetric systems for the 100-120kV range, the very high uncertainty of the TL dosimeters in comparison to the other systems and high nonlinearity response in terms of air kerma of the radiochromic film. Measurements with the three systems in a 120kV CT protocol showed an acceptable agreement among the weighted air kerma index values, but TL dosimeters presented the highest uncertainties in the values.
Assuntos
Radiometria/métodos , Tomografia Computadorizada por Raios X , Dosimetria Fotográfica/métodos , Dosimetria Fotográfica/estatística & dados numéricos , Humanos , Imagens de Fantasmas , Radiometria/instrumentação , Radiometria/estatística & dados numéricos , Dosimetria Termoluminescente/métodos , Dosimetria Termoluminescente/estatística & dados numéricos , Filme para Raios XRESUMO
During a lung computed tomography (CT) examination, breast and nearby radiosensitive organs are unnecessarily irradiated because they are in the path of the primary beam. The purpose of this paper is to determine the absorbed dose in breast and nearby organs for unshielded and shielded exposures with bismuth. The experiment was done with a female anthropomorphic phantom undergoing a typical thoracic CT scan, with TLD-100 thermoluminescent detectors insert at breast, lung and thyroid positions. Results showed that dose reduction due to bismuth shielding was approximately 30% and 50% for breast and thyroid, respectively; however, the influence of the bismuth on the image quality needs to be considered.
Assuntos
Absorção de Radiação/fisiologia , Bismuto/química , Mama/fisiologia , Exposição à Radiação/análise , Proteção Radiológica/instrumentação , Radiografia Torácica/métodos , Tomografia Computadorizada por Raios X/métodos , Mama/efeitos da radiação , Desenho de Equipamento , Feminino , Humanos , Órgãos em Risco/efeitos da radiação , Imagens de Fantasmas , Doses de Radiação , Proteção Radiológica/métodosRESUMO
A new regulatory statement was issued concerning the eye lens radiation protection of persons in planned exposures. A debate was raised on the adequacy of the dosimetric quantity and on its method of measurement. The aim of this work was to establish the individual monitoring procedure with the EYE-D™ holder and a MCP-N LiF:Mg,Cu,P thermoluminescent chip detector for measuring the personal dose equivalent Hp(3) in workers of a Positron Emission Tomography Radiopharmaceutical Production Facility.
Assuntos
Cristalino/fisiologia , Cristalino/efeitos da radiação , Exposição Ocupacional/análise , Tomografia por Emissão de Pósitrons/métodos , Exposição à Radiação/análise , Dosimetria Termoluminescente/instrumentação , Brasil/epidemiologia , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Compostos Radiofarmacêuticos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Dosimetria Termoluminescente/métodosRESUMO
OBJECTIVE: The aim of this human study was to evaluate the radiation doses in the buccal cavity and face, during panoramic, spiral conventional tomography, and helicoidal computerized tomography exams. MATERIAL AND METHODS: Lithium fluoride TL detectors (TLD-100) were placed on the skin at anatomic points such as parotid glands, submandibular glands, thyroid glands, and crystalline to assess the skin entrance dose in 19 patients who were to undergo dental implant surgery. RESULTS: In the panoramic exam, maximum doses were observed near the parotid glands at 1.57 (±18%) mGy on the right and 1.89 (±18%) mGy on the left. In the spiral conventional tomography exam, the maximum dose was 4.41 (±21%) mGy near the right and left parotid glands, whereas near the right or left submandibular glands, the maximum doses reached 40.7 (±18%) mGy. In the helicoidal computerized tomography for mandibular and maxilla exams, the maximum dose was 40.9 (±15%) mGy near the parotid glands and 41.0 (±18%) mGy near the submandibular glands. Near the thyroid and eye lens, doses were lower than 0.23 (±21%) in all exams. CONCLUSION: Regardless of the exam target area, the submandibular and parotid glands represented the most irradiated organs. This data suggests that efforts should be made by professionals to improve and optimize methods in order to reduce doses without losing the information necessary for treatment planning.
