RESUMO
The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation.
Assuntos
Espectroscopia de Ressonância de Spin Eletrônica/métodos , Odontologia Legal/métodos , Radioisótopos/análise , Radiometria/métodos , Dente/química , Espectroscopia de Ressonância de Spin Eletrônica/tendências , Odontologia Legal/tendências , Humanos , Radiometria/tendências , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.
Assuntos
Espectroscopia de Ressonância de Spin Eletrônica/métodos , Espectroscopia de Ressonância de Spin Eletrônica/normas , Radiometria/métodos , Radiometria/normas , Padrões de Referência , Dente/química , Dente/efeitos da radiação , Benchmarking/métodos , Carga Corporal (Radioterapia) , Humanos , Técnicas In Vitro , Internacionalidade , Garantia da Qualidade dos Cuidados de Saúde/métodos , Garantia da Qualidade dos Cuidados de Saúde/normas , Doses de Radiação , Eficiência Biológica Relativa , Reprodutibilidade dos Testes , Estudos Retrospectivos , Medição de Risco/métodos , Medição de Risco/normas , Sensibilidade e EspecificidadeRESUMO
The tooth enamel EPR signal at g = 1.9973 consists of several components, which correspond to different functions of the spatial orientation of the CO2- radicals, have different temperature stability and different saturation curves. Using a new technique described in this paper, we have detected and investigated two groups of CO2- radicals with different thermal stability and saturation characteristics.
Assuntos
Carbonatos/análise , Esmalte Dentário/química , Esmalte Dentário/efeitos da radiação , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Carbonatos/efeitos da radiação , Humanos , Radiometria/métodos , TemperaturaRESUMO
Peculiarities of the internal construction of tooth enamel and bones that cause anisotropy effects and mass transfer in these objects are described. It is shown that the composition of the mineral component of teeth and bones depends on a mechanical-electrical mechanism, which pumps ions into nanocrystals. Decrease in the efficiency of the mechanical-electrical mechanism results in demineralization of enamel and bones, which progresses most rapidly at a disease of the biomineral or under special conditions, such as in space flights. Effects of signal anisotropy in the practice of retrospective EPR dosimetry are discussed.
Assuntos
Osso e Ossos/química , Osso e Ossos/efeitos da radiação , Esmalte Dentário/química , Esmalte Dentário/efeitos da radiação , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Animais , Anisotropia , Carbonatos/análise , Radicais Livres , Humanos , Minerais/análise , Modelos Biológicos , Radiometria/métodos , RatosRESUMO
It is shown that metamorphic modifications in tooth enamel have an essential influence on the results of EPR dosimetry. The metamorphic modifications in minerals of biological origin proceed more quickly than in usual natural minerals. The approaches which at present are applied for reconstruction of doses connected with Chernobyl accident need additional investigation.