Evaluation of conversion coefficients relating air-kerma toH*(10) using primary and transmitted x-ray spectra in the diagnostic radiology energy range

Abstract

According to the International Commission on Radiation Units and Measurements (ICRU), the relationship between effective dose and incident air-kerma is complex and depends on the attenuation of x-rays in the body. Therefore, it is not practical to use this quantity for shielding design purposes. This correlation is adopted in practical situations by using conversion coefficients calculated using validated mathematical models by the ICRU. The ambient dose equivalent, H*(10), is a quantity adopted by the IAEA for monitoring external exposure. Dose constraint levels are established in terms of H*(10), while the radiation levels in radiometric surveys are calculated by means of the measurements of air-kerma with ion chambers. The resulting measurements are converted into ambient dose equivalents by conversion factors. In the present work, an experimental study of the relationship between the air-kerma and the operational quantity ambient dose equivalent was conducted using different experimental scenarios. This study was done by measuring the primary x-ray spectra and x-ray spectra transmitted through materials used in dedicated chest radiographic facilities, using a CdTe detector. The air-kerma to ambient dose equivalent conversion coefficients were calculated from these measured spectra. The resulting values of the quantity ambient dose equivalent using these conversion coefficients are more realistic than those available in the literature, because they consider the real energy distribution of primary and transmitted x-ray beams. The maximum difference between the obtained conversion coefficients and the constant value recommended in national and international radiation protection standards is 53.4%. The conclusion based on these results is that a constant coefficient may not be adequate for deriving the ambient dose equivalent.

Effects of Low-Energy Laser Irradiation on Sperm Cells Dynamics of Rabbit (Oryctolagus Cuniculus)

“…The energy calibration of the spectrometer was done using standard radiation sources of 241 Am, 152 Eu and 133 Ba. The measured transmitted x-ray spectra were corrected by the detector efficiency, estimated using Monte Carlo method (Tomal et al (2015)), Compton distortion and fluorescent escape fraction were reduced or removed using stripping procedure (Di Castro et al (1984); Santos et al (2016)). In this way, the corrected x-ray spectra are presented in units of fluence normalized by the current-time product (photons/ mm 2 .mAs.keV).…”

Determinação da camada semirredutora e da tensão aplicada a partir de espectros emitidos por um tubo de raios X

“…Porém, complexidades técnicas no processo de medições destes espectros dificultaram por muito tempo a aplicação da espectrometria em condições clínicas para avaliar feixes de radiodiagnostico. No entanto, com o surgimento dos sistemas de espectrometria portáteis, o uso dessa técnica tem sido ampliado, incluindo aplicações para avaliação de espectros de raios X de feixes clínicos para fins de pesquisa [2][3][4][5][6][7][8] .…”

“…Pode-se, ainda, obter valores de kVp não-invasivamente a partir de penetrâmetros 10 ou dos espectros dos feixes medidos com espectrômetros compostos por detectores cintiladores ou semicondutores 7,8 . A determinação do valor de maior energia (end point) do espectro medido [11][12] , estimado por meio de regressão linear nos últimos canais do espectro, pode apresentar alto grau de precisão e servir como referência para calibração de medidores invasivos ou não-invasivos de kVp 11 .…”

Desenvolvimento de método de análise de materiais equivalentes ao tecido humano por simulação Monte Carlo

“…These input spectra were corrected for the detection distortion effects (Di Castro et al 1984;Kurková and Judas 2015). The present work used Di Castro's et al stripping method, as described by Santos et al (Santos et al 2016). The used detection efficiency curves and escape factors are specific for the used CdTe detector and for mammographic energy range and were estimated by Tomal et al (Tomal et al 2012;Tomal et al 2015).…”

“…One way of performing X-ray spectrometry using clinical radiation beams is with solid-state detectors biased by an electrical field and linked to a Multi-Channel Analyzer (MCA) (Abbene et al 2012;Bottigli et al 2006;Kurková and Judas 2015;Miyajima 2003;Miyajima et al 2002;Santos et al 2016). Care must be taken because the correct quantitative determination of the measured spectra can only be achieved after careful corrections according to the response curve of the detector are performed (García-Alvarez et al 2016;LeClair et al 2006;Nunn et al 2008;Tomal et al 2012;Tomal et al 2015).…”