Direct measurement of clinical mammographic x-ray spectra using a CdTe spectrometer.

Autor: Santos JC; Instituto de Física, Universidade de São Paulo, São Paulo, SP, 05508-090, Brazil., Tomal A; Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Campinas, SP, 13083-859, Brazil., Furquim TA; Instituto de Física, Universidade de São Paulo, São Paulo, SP, 05508-090, Brazil., Fausto AMF; Departamento de Ciências Exatas e Tecnológicas, Universidade Estadual de Santa Cruz, Ilhéus, BA, 45662-900, Brazil., Nogueira MS; Centro de Desenvolvimento de Tecnologia Nuclear, Comissão Nacional de Energia Nuclear, Belo Horizonte, MG, 31270-901, Brazil., Costa PR; Instituto de Física, Universidade de São Paulo, São Paulo, SP, 05508-090, Brazil.
Jazyk: angličtina
Zdroj: Medical physics [Med Phys] 2017 Jul; Vol. 44 (7), pp. 3504-3511. Date of Electronic Publication: 2017 May 26.
DOI: 10.1002/mp.12287
Abstrakt: Purpose: To introduce and evaluate a method developed for the direct measurement of mammographic x-ray spectra using a CdTe spectrometer. The assembly of a positioning system and the design of a simple and customized alignment device for this application is described.
Methods: A positioning system was developed to easily and accurately locate the CdTe detector in the x-ray beam. Additionally, an alignment device to line up the detector with the central axis of the radiation beam was designed. Direct x-ray spectra measurements were performed in two different clinical mammography units and the measured x-ray spectra were compared with computer-generated spectra. In addition, the spectrometer misalignment effect was evaluated by comparing the measured spectra when this device is aligned relatively to when it is misaligned.
Results: The positioning and alignment of the spectrometer have allowed the measurements of direct mammographic x-ray spectra in agreement with computer-generated spectra. The most accurate x-ray spectral shape, related with the minimal HVL value, and high photon fluence for measured spectra was found with the spectrometer aligned according to the proposed method. The HVL values derived from both simulated and measured x-ray spectra differ at most 1.3 and 4.5% for two mammography devices evaluated in this study.
Conclusion: The experimental method developed in this work allows simple positioning and alignment of a spectrometer for x-ray spectra measurements given the geometrical constraints and maintenance of the original configurations of mammography machines.
(© 2017 American Association of Physicists in Medicine.)
Databáze: MEDLINE
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