Effective atomic numbers (Zeff) of based calcium phosphate biomaterials: a comparative study.

This study determined the interaction of radiation parameters of four biomaterials as attenuators to measure the transmitted X-rays spectra, the mass attenuation coefficient and the effective atomic number by spectrometric system comprising the CdTe detector. The biomaterial BioOss® presented smaller mean energy than the other biomaterials. The µ/ρ and Zeff of the biomaterials showed their dependence on photon energy. The data obtained from analytical methods of x-ray spectra, µ/ρ and Zeff, using biomaterials as attenuators, demonstrated that these materials could be used as substitutes for dentin, enamel and bone. Further, they are determinants for the characterization of the radiation in tissues or equivalent materials.

Ambient radiation levels in positron emission tomography/computed tomography (PET/CT) imaging center.

OBJECTIVE: To evaluate the level of ambient radiation in a PET/CT center. MATERIALS AND METHODS: Previously selected and calibrated TLD-100H thermoluminescent dosimeters were utilized to measure room radiation levels. During 32 days, the detectors were placed in several strategically selected points inside the PET/CT center and in adjacent buildings. After the exposure period the dosimeters were collected and processed to determine the radiation level. RESULTS: In none of the points selected for measurements the values exceeded the radiation dose threshold for controlled area (5 mSv/year) or free area (0.5 mSv/year) as recommended by the Brazilian regulations. CONCLUSION: In the present study the authors demonstrated that the whole shielding system is appropriate and, consequently, the workers are exposed to doses below the threshold established by Brazilian standards, provided the radiation protection standards are followed.

OBJETIVO: Avaliar o nível de radiação no ambiente de um serviço de PET/CT. MATERIAIS E MÉTODOS: Para a determinação dos níveis de radiação no ambiente foram utilizados dosímetros termoluminescentes TLD-100H previamente selecionados e calibrados. Estes detectores foram expostos durante 32 dias em diversos pontos estrategicamente escolhidos nas dependências do serviço e nos prédios adjacentes. Após o período de exposição, os dosímetros foram recolhidos e processados. RESULTADOS: Em nenhum dos pontos avaliados os valores medidos ultrapassaram os limites de restrição de dose para área controlada (5 mSv/ano) ou para área livre (0,5 mSv/ano) recomendados pelas normas brasileiras. CONCLUSÃO: Com este trabalho foi possível demonstrar que todas as blindagens do serviço estão adequadas e que, consequentemente, os trabalhadores, desde que seguindo as normas de radioproteção, receberão doses abaixo da dose de restrição indicada no Brasil.

Determination of dosimetric quantities in pediatric abdominal computed tomography scans.

OBJECTIVE: Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL). MATERIALS AND METHODS: The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom. RESULTS: No significant difference was observed in the values for weighted air kerma index (CW), but the differences were relevant in values for volumetric air kerma index (CVOL), air kerma-length product (PKL,CT) and effective dose. CONCLUSION: Only the CW values were lower than the DRL, suggesting that dose optimization might not be necessary. However, PKL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans.

OBJETIVO: Visando contribuir para o conhecimento das doses em tomografia computadorizada (TC), este trabalho teve o objetivo de quantificar grandezas dosimétricas associadas a exames do abdome em pacientes pediátricos, comparando-as com os níveis de referência em radiodiagnóstico (NRD). MATERIAIS E MÉTODOS: O estudo foi realizado em dois hospitais, em um tomógrafo Toshiba Asteion single-slice e um GE BrightSpeed multi-slice. Medidas foram feitas com uma câmara de ionização tipo lápis e um objeto simulador de tronco de polimetilmetacrilato de 16 cm de diâmetro. RESULTADOS: Os valores do índice ponderado de kerma no ar (CW) não apresentaram diferenças significativas, porém, para as grandezas índice de kerma no ar volumétrico (CVOL), produto kerma-comprimento (PKL,CT) e dose efetiva, as diferenças foram relevantes. CONCLUSÃO: Apenas o CW apresentou valores menores que os NRD, sugerindo que a otimização não seria necessária. Porém, os valores de PKL,CT e dose efetiva mostraram que há espaço para reduzir as doses de radiação pediátricas. Este trabalho ressalta a importância de avaliar todas as grandezas dosimétricas associadas aos exames por TC.

Dosimetry of patients submitted to cerebral PET/CT for the diagnosis of mild cognitive impairment.

OBJECTIVE: The present study was aimed at evaluating the effective radiation dose in patients submitted to PET/CT for the diagnosis of mild cognitive impairment. MATERIALS AND METHODS: TLD-100 detectors inserted into an Alderson Rando® anthropomorphic phantom were utilized to measure the absorbed dose coming from the CT imaging modality. The anthropomorphic phantoms (male and female adult versions) were submitted to the same technical protocols for patients' images acquisition. The absorbed dose resulting from the radiopharmaceutical injection was estimated by means of the model proposed by the ICRP publication 106. RESULTS: The effective dose in patients submitted to this diagnostic technique was approximately (5.34 ± 1.99) mSv. CONCLUSION: Optimized protocols for calculation of radioactive activity injected into patients submitted to this diagnostic technique might contribute to reduce the effective radiation dose resulting from PET/CT in the diagnosis of mild cognitive impairment.

OBJETIVO: O objetivo deste trabalho é avaliar a dose em pacientes submetidos a PET/CT para diagnóstico de comprometimento cognitivo leve. MATERIAIS E MÉTODOS: Para as medidas da dose absorvida proveniente da modalidade CT utilizaram-se detectores TLD-100 inseridos em um simulador Alderson Rando®. Os simuladores antropomórficos (versões masculina e feminina) foram submetidos aos mesmos protocolos técnicos para aquisição das imagens dos pacientes. A dose absorvida resultante da injeção do radiofármaco foi estimada por meio do modelo proposto pela ICRP 106. RESULTADOS: A dose efetiva a que foram submetidos os pacientes com esta técnica diagnóstica foi, aproximadamente, (5,34 ± 1,99) mSv. CONCLUSÃO: Protocolos otimizados para cálculo de atividade radioativa que será injetada em cada paciente podem contribuir para a redução da dose efetiva nos pacientes durante a realização do diagnóstico de comprometimento cognitivo leve com PET/CT.

Evaluation of a technique for in vivo internal monitoring of (18)F within a Brazilian laboratory network.

(18)FDG, an analogue of glucose labelled with the radionuclide (18)F, is the most widely used radiopharmaceutical in positron emission tomography/computed tomography technique. In Brazil, there are currently eight (18)FDG plants in operation and other facilities are expected to start their production in the near future. The growth in the production and clinical use of (18)FDG represents an increasing risk of worker exposures. According to national regulations and international recommendations, internal exposures should be effectively controlled in order to keep doses as low as possible. The implementation of a routine monitoring programme towards the estimation of internal doses related to the incorporation of (18)F is difficult, mainly due to its short physical half-life, the cost of a bioassay laboratory and the need of a monitoring service promptly available near the production plant. This paper describes the implementation and evaluation of a methodology for in vivo brain monitoring of (18)F to be applied in cases of suspected incorporation of (18)FDG. The technique presented a minimum detectable effective dose in the order of nanoSieverts, which allows its application for occupational monitoring purposes.

Assessment of dosimetric quantities for patients undergoing X-ray examinations in a large public hospital in Brazil--a preliminary study.

The introduction of routine patient dosimetry to Brazilian radiological institutions is very necessary in order to meet national and international standard requirements for radiation protection. This work presents a survey of the air kerma-area product (P(KA)), the entrance surface air kerma (K(e)) and the effective dose (E) in common radiographic examinations during the routine of a large public hospital in the city of Belo Horizonte, Brazil. Results draw attention to the use of field sizes larger than the cassette dimension, the lack of both the collimation X-ray beam and the standardisation of the exposure parameters by radiology technicians.