Spectroscopy of diagnostic x rays by a Compton‐scatter method

Yaffe, Martin J.; Taylor, Kenneth W.; Johns, H. E.

doi:10.1118/1.594263

Cited by 74 publications

(43 citation statements)

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“…Vários pesquisadores 3,4 , no passado, mediram o espectro de feixes de raios X de equipamentos clínicos por meio de espectrometria Compton, usando detetores de Ge e espalhadores de lucite ou carbono.…”

Section: Introductionunclassified

Caracterização de feixes de TC utilizando Espectrometria Compton

et al. 2017

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ResumoÉ essencial obter espectros dos raios X em tomografia computadorizada (TC), visando obter parâmetros que caracterizam a qualidade do feixe e o desempenho do equipamento. Entretanto, os fluxos de fótons em TC são demasiado elevados para se medir os espectros diretamente com detetores comuns. Neste trabalho, foi projetado um espectrômetro Compton, com um detetor de telureto de cádmico (CdTe), para obter o espectro de feixes de TC, a partir da medição do espectro do feixe espalhado a 90 o por uma haste de polimetil-metacrilato (PMMA). Um programa de computador foi desenvolvido em MatLab®, usando o formalismo de Waller-Hartree, para reconstruir os espectros incidentes no espalhador, a partir dos espectros dos feixes espalhados medidos. Medições no LDRFM, com feixes padronizados de TC, mostraram que o espectro reconstruído é semelhante ao do feixe medido diretamente. A influência da blindagem e da espessura do espalhador foram investigadas. O sistema foi testado em um scanner GE 690, permitindo posicionamento na mesa de exames e alinhamento com lasers, refinado por radiografia do sistema. Com o sistema adequadamente blindado, os espectros obtidos apresentaram valores de camada semi-redutora (CSR) compatíveis com aqueles medidos em testes de controle de qualidade e valores de kVp com precisão suficiente para avaliar a calibração em tensão do scanner. Palavras-chave: Espectrometria Compton, tomografia computadorizada, detector de CdTe, feixes espalhados. Abstract Obtaining the energy spectra of computed tomography (CT) X-ray beams is essential, helping to obtain

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Section: Introductionunclassified

Caracterização de feixes de TC utilizando Espectrometria Compton

et al. 2017

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“…[7][8][9][10][11][12][13][14][15][16] The transmission method is one of the measurement-based methods. This method is relatively simple and has been implemented in a large range of x-ray energies.…”

Section: Introductionmentioning

confidence: 99%

CT scanner x‐ray spectrum estimation from transmission measurements

Duan¹,

Wang²,

Yu³

et al. 2011

Medical Physics

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Purpose:In diagnostic CT imaging, multiple important applications depend on the knowledge of the x-ray spectrum, including Monte Carlo dose calculations and dual-energy material decomposition analysis. Due to the high photon flux involved, it is difficult to directly measure spectra from the x-ray tube of a CT scanner. One potential method for indirect measurement involves estimating the spectrum from transmission measurements. The expectation maximization ͑EM͒ method is an accurate and robust method to solve this problem. In this article, this method was evaluated in a commercial CT scanner. Methods: Two step-wedges ͑polycarbonate and aluminum͒ were used to produce different attenuation levels. Transmission measurements were performed on the scanner and the measured data from the scanner were exported to an external computer to calculate the spectra. The EM method was applied to solve the equations that represent the attenuation processes of polychromatic x-ray photons. Estimated spectra were compared to the spectra simulated using a software provided by the manufacturer of the scanner. To test the accuracy of the spectra, a verification experiment was performed using a phantom containing different depths of water. The measured transmission data were compared to the transmission values calculated using the estimated spectra. Results: Spectra of 80, 100, 120, and 140 kVp from a dual-source CT scanner were estimated. The estimated and simulated spectra were well matched. The differences of mean energies were less than 1 keV. In the verification experiment, the measured and calculated transmission values were in excellent agreement. Conclusions: Spectrum estimation using transmission data and the EM method is a quantitatively accurate and robust technique to estimate the spectrum of a CT system. This method could benefit studies relying on accurate knowledge of the x-ray spectra from CT scanner.

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“…On the other hand, scatterers of high atomic number produce energy broadening due to the Compton profile because the mean binding energy increases with the increasing atomic number 1) . The Compton spectroscopy technique was realized by Yaffe et al to measure x-ray spectra from diagnostic x-ray tubes 2) . In this study, a Lucite foil disc was used as a scattered.…”

Section: Introductionmentioning

confidence: 99%

On the Use of a Thick Carbon Target in the 90° Compton Spectroscopy for the Measurement of Diagnostic X-rays

Mohammadi

Baba

Ohuchi

et al. 2008

Journal of Nuclear Science and Technology

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In order to perform quality assurance (QA) and quality control (QC) of the X-ray radiographic systems, we studied the Compton spectroscopy using different shape and size of scatterer such as columnar carbon rods of 2 cm diameter, which were cut at different angles of 15º, 30º, 45º, 60º and 75º. The appropriate shape of a carbon scatterer was studied in terms of minimum multiple scattering, the energy broadening and easy practical use. Calculated exposure results from our Compton spectroscopy using two scatteres were confirmed by the results of exposure measurement using a calibrated ionization chamber. The Compton spectroscopy of x-ray radiographic systems with a thick carbon scatterer proved to be a useful method for the evaluation of such system performance.

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Spectroscopy of diagnostic x rays by a Compton‐scatter method

Cited by 74 publications

References 0 publications

Caracterização de feixes de TC utilizando Espectrometria Compton

Caracterização de feixes de TC utilizando Espectrometria Compton

CT scanner x‐ray spectrum estimation from transmission measurements

On the Use of a Thick Carbon Target in the 90° Compton Spectroscopy for the Measurement of Diagnostic X-rays

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