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Title: Quantifying the effect of anode surface roughness on diagnostic x-ray spectra using Monte Carlo simulation

Abstract

Purpose: The accurate prediction of x-ray spectra under typical conditions encountered in clinical x-ray examination procedures and the assessment of factors influencing them has been a long-standing goal of the diagnostic radiology and medical physics communities. In this work, the influence of anode surface roughness on diagnostic x-ray spectra is evaluated using MCNP4C-based Monte Carlo simulations. Methods: An image-based modeling method was used to create realistic models from surface-cracked anodes. An in-house computer program was written to model the geometric pattern of cracks and irregularities from digital images of focal track surface in order to define the modeled anodes into MCNP input file. To consider average roughness and mean crack depth into the models, the surface of anodes was characterized by scanning electron microscopy and surface profilometry. It was found that the average roughness (R{sub a}) in the most aged tube studied is about 50 {mu}m. The correctness of MCNP4C in simulating diagnostic x-ray spectra was thoroughly verified by calling its Gaussian energy broadening card and comparing the simulated spectra with experimentally measured ones. The assessment of anode roughness involved the comparison of simulated spectra in deteriorated anodes with those simulated in perfectly plain anodes considered as reference. From thesemore » comparisons, the variations in output intensity, half value layer (HVL), heel effect, and patient dose were studied. Results: An intensity loss of 4.5% and 16.8% was predicted for anodes aged by 5 and 50 {mu}m deep cracks (50 kVp, 6 deg. target angle, and 2.5 mm Al total filtration). The variations in HVL were not significant as the spectra were not hardened by more than 2.5%; however, the trend for this variation was to increase with roughness. By deploying several point detector tallies along the anode-cathode direction and averaging exposure over them, it was found that for a 6 deg. anode, roughened by 50 {mu}m deep cracks, the reduction in exposure is 14.9% and 13.1% for 70 and 120 kVp tube voltages, respectively. For the evaluation of patient dose, entrance skin radiation dose was calculated for typical chest x-ray examinations. It was shown that as anode roughness increases, patient entrance skin dose decreases averagely by a factor of 15%. Conclusions: It was concluded that the anode surface roughness can have a non-negligible effect on output spectra in aged x-ray imaging tubes and its impact should be carefully considered in diagnostic x-ray imaging modalities.« less

Authors:
; ; ;  [1]
  1. Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran (Iran, Islamic Republic of) and Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, P.O. Box 14185-615, Tehran (Iran, Islamic Republic of)
Publication Date:
OSTI Identifier:
22096631
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 37; Journal Issue: 2; Other Information: (c) 2010 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; ANODES; COMPARATIVE EVALUATIONS; COMPUTER CODES; COMPUTERIZED SIMULATION; CRACKS; IMAGE PROCESSING; MONTE CARLO METHOD; PATIENTS; RADIATION DOSES; RADIOLOGY; SCANNING ELECTRON MICROSCOPY; SKIN; SURFACES; X RADIATION; X-RAY SPECTRA; X-RAY TUBES

Citation Formats

Mehranian, A., Ay, M. R., Alam, N. Riyahi, Zaidi, H., Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran, Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, P.O. Box 14185-615, Tehran, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran, and Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva. Quantifying the effect of anode surface roughness on diagnostic x-ray spectra using Monte Carlo simulation. United States: N. p., 2010. Web. doi:10.1118/1.3284212.
Mehranian, A., Ay, M. R., Alam, N. Riyahi, Zaidi, H., Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran, Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, P.O. Box 14185-615, Tehran, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran, & Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva. Quantifying the effect of anode surface roughness on diagnostic x-ray spectra using Monte Carlo simulation. United States. https://doi.org/10.1118/1.3284212
Mehranian, A., Ay, M. R., Alam, N. Riyahi, Zaidi, H., Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran, Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, P.O. Box 14185-615, Tehran, Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran, and Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva. 2010. "Quantifying the effect of anode surface roughness on diagnostic x-ray spectra using Monte Carlo simulation". United States. https://doi.org/10.1118/1.3284212.
@article{osti_22096631,
title = {Quantifying the effect of anode surface roughness on diagnostic x-ray spectra using Monte Carlo simulation},
author = {Mehranian, A. and Ay, M. R. and Alam, N. Riyahi and Zaidi, H. and Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran and Research Center for Science and Technology in Medicine, Tehran University of Medical Sciences, P.O. Box 14185-615, Tehran and Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, P.O. Box 14155-6447, Tehran and Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva},
abstractNote = {Purpose: The accurate prediction of x-ray spectra under typical conditions encountered in clinical x-ray examination procedures and the assessment of factors influencing them has been a long-standing goal of the diagnostic radiology and medical physics communities. In this work, the influence of anode surface roughness on diagnostic x-ray spectra is evaluated using MCNP4C-based Monte Carlo simulations. Methods: An image-based modeling method was used to create realistic models from surface-cracked anodes. An in-house computer program was written to model the geometric pattern of cracks and irregularities from digital images of focal track surface in order to define the modeled anodes into MCNP input file. To consider average roughness and mean crack depth into the models, the surface of anodes was characterized by scanning electron microscopy and surface profilometry. It was found that the average roughness (R{sub a}) in the most aged tube studied is about 50 {mu}m. The correctness of MCNP4C in simulating diagnostic x-ray spectra was thoroughly verified by calling its Gaussian energy broadening card and comparing the simulated spectra with experimentally measured ones. The assessment of anode roughness involved the comparison of simulated spectra in deteriorated anodes with those simulated in perfectly plain anodes considered as reference. From these comparisons, the variations in output intensity, half value layer (HVL), heel effect, and patient dose were studied. Results: An intensity loss of 4.5% and 16.8% was predicted for anodes aged by 5 and 50 {mu}m deep cracks (50 kVp, 6 deg. target angle, and 2.5 mm Al total filtration). The variations in HVL were not significant as the spectra were not hardened by more than 2.5%; however, the trend for this variation was to increase with roughness. By deploying several point detector tallies along the anode-cathode direction and averaging exposure over them, it was found that for a 6 deg. anode, roughened by 50 {mu}m deep cracks, the reduction in exposure is 14.9% and 13.1% for 70 and 120 kVp tube voltages, respectively. For the evaluation of patient dose, entrance skin radiation dose was calculated for typical chest x-ray examinations. It was shown that as anode roughness increases, patient entrance skin dose decreases averagely by a factor of 15%. Conclusions: It was concluded that the anode surface roughness can have a non-negligible effect on output spectra in aged x-ray imaging tubes and its impact should be carefully considered in diagnostic x-ray imaging modalities.},
doi = {10.1118/1.3284212},
url = {https://www.osti.gov/biblio/22096631}, journal = {Medical Physics},
issn = {0094-2405},
number = 2,
volume = 37,
place = {United States},
year = {Mon Feb 15 00:00:00 EST 2010},
month = {Mon Feb 15 00:00:00 EST 2010}
}