Dose reduction evaluation in radiosensitive tissues for head CT scans using two phantoms and bismuth eye shielding

Authors

  • Lorena Cunha Fernandes
  • Arnaldo Prata Mourão Universidade Federal de Minas Gerais / Departamento de Engenharia Nuclear

DOI:

https://doi.org/10.15392/bjrs.v10i3.2040

Keywords:

Computed tomography, bismuth eye shielding, dosimetry, radiochromic film

Abstract

Computed tomography is the imaging technique that most contributes to increasing the population average dose. Head scanning protocols have a very high dose in patients due to the small thicknesses of the slice for 3D image reconstruction. In this sense, radiosensitive tissues, such as the eye lenses and the thyroid, receive significant doses, as they are close to or in the irradiated field. The objective of this work is to present data on the variation of absorbed dose in the eye lenses and thyroid, with and without the use of bismuth eye shielding in head CT scans, and also to analyze the best dose-to-noise ratio in order to observe whether there is a decrease in image quality capable of rendering the proposed protocols useless. The method is based on head scans testing optimized protocols for the radiology service. Two male phantoms, one anthropomorphic and the other made in polymethyl methacrylate (PMMA), were used in the tests and radiochromic films were used to measure the absorbed dose values. The films were placed in the eye lenses and thyroid regions. Scans were performed on a GE CT scanner with 64-channel, Light Speed model. The obtained data allowed to observe the dose variation in the tissues and to conclude which of used protocols presented has the best noise-to-dose ratio for the use of the bismuth eye shielding. The results obtained will be important to suggest a complementary procedure for the optimization of head CT scans.

Downloads

Download data is not yet available.

References

Thurston, Jim. NCRP Report No. 160: ionizing radiation exposure of the population of the United States. 2010. DOI: https://doi.org/10.1088/0031-9155/55/20/6327

ICRP. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103 (2007). Ann. ICRP, Volume 37, p. 1-332.

CHODICK, G. et al. Risk of cataract after exposure to low doses of ionizing radiation: a 20-year prospective cohort study among US radiologic technologists. American journal of epidemiology, v. 168, n. 6, p. 620-631, 2008. DOI: https://doi.org/10.1093/aje/kwn171

YUAN, Mei-Kang et al. The risk of cataract associated with repeated head and neck CT studies: a nationwide population-based study. American Journal of Roentgenology, v. 201, n. 3, p. 626-630, 2013. DOI: https://doi.org/10.2214/AJR.12.9652

National Council on Radiation Protection and Measurements. Guidance on Radiation Dose Limits for the Lens of the Eye, NCRP Commentary No. 26. National Council on Radiation Protection and Measurements, Bethesda, Maryland, 2016.

SCHONFELD, S. J.; LEE, C.; DE GONZALEZ, A. B.. Medical exposure to radiation and thyroid cancer. Clinical Oncology, v. 23, n. 4, p. 244-250, 2011. DOI: https://doi.org/10.1016/j.clon.2011.01.159

Baker, Stephen R.; BHATTI, Waseem A. The thyroid cancer epidemic: is it the dark side of the CT revolution?. European journal of radiology, v. 60, n. 1, p. 67-69, 2006. DOI: https://doi.org/10.1016/j.ejrad.2006.04.022

TIPNIS, S. V. et al. Thyroid doses and risks to adult patients undergoing neck CT examinations. American Journal of Roentgenology, v. 204, n. 5, p. 1064-1068, 2015. DOI: https://doi.org/10.2214/AJR.14.13102

CIARMATORI, A. et al. Reducing absorbed dose to eye lenses in head CT examinations: the effect of bismuth shielding. Australasian physical & engineering sciences in medicine, v. 39, n. 2, p. 583-589, 2016. DOI: https://doi.org/10.1007/s13246-016-0445-y

OMER, Hiba et al. Eye lens and thyroid gland radiation exposure for patients undergoing brain computed tomography examination. Saudi Journal of Biological Sciences, v. 28, n. 1, p. 342-346, 2021. DOI: https://doi.org/10.1016/j.sjbs.2020.10.010

International Atomic Energy Agency (IAEA). Radiation and cataract: staff protection. Available at: <https://www.iaea.org/resources/rpop/health-professionals/radiology/cataract/patients> Last accessed: 19 Nov. 2020.

LIN, Ming-Fang et al. Topogram-based tube current modulation of head computed tomography for optimizing image quality while protecting the eye lens with shielding. Acta Radiologica, v. 60, n. 1, p. 61-67, 2019. DOI: https://doi.org/10.1177/0284185118770894

LEE, Jong-Woong; KWEON, Dae Cheol. Assessment of dose reduction and image quality by barium composite shielding in head and chest CT. Radiation Effects and Defects in Solids, p. 1-18, 2020.

BANGASSI, T. N. K.; SAMBA, O. N.; THIERENS, H.; BACHER, K. Eye Lens Dose Reduction in Head CT Using Bismuth Shielding: Application in CT Facility in Cameroon. AASCIT Journal of Health, vol.5,nº1. pg 11-15, 2018.

Radiopaedia. Beam hardening. Available at: <https://radiopaedia.org/articles/beam-hardening> Last accessed: 19 Nov. 2020.

LAI, C. W. K. et al. Reducing the radiation dose to the eye lens region during CT brain examination: the potential beneficial effect of the combined use of bolus and a bismuth shield. Radioprotection, v. 50, n. 3, p. 195-201, 2015. DOI: https://doi.org/10.1051/radiopro/2015003

SALINAS, C. Leiva et al. Bismuth shielding at head CT: Impact of a novel design on the image quality and dose reduction to the lens. ECR 2015, 2015.

GIADDUI, T. et al. Characteristics of Gafchromic XRQA2 films for kV image dose measurement. Medical physics, v. 39, n. 2, p. 842-850, 2012. DOI: https://doi.org/10.1118/1.3675398

BioSmith. Eye shield. Available at: < https://www.fandlmedicalproducts.com/AttenuRad-CT-Eye-Shield.html > Last accessed: 19 Jan. 2021.

RASBAND, W. S. ImageJ, U. S. National Institutes of Health. Bethesda, Maryland, USA. 2011. Available at: <http://imagej.nih.gov/ij/>. Last accessed: 19 Nov. 2020.

MOURÃO, A. P.; ALONSO, T. C.; DASILVA, T. A. Dose profile variation with voltage in head CT scans using radiochromic films. Radiation Physics and Chemistry, v. 95, p. 254-257, 2014. DOI: https://doi.org/10.1016/j.radphyschem.2013.05.013

RAMPADO, O.; GARELLI, E.; ROPOLO, R. Computed tomography dose measurements with radiochromic films and a flatbed scanner. Medical physics, v. 37, n. 1, p. 189-196, 2010. DOI: https://doi.org/10.1118/1.3271584

RadiAnt DICOM Viewer. Available at: <https://www.radiantviewer.com/dicom-viewer-manual/>. Last accessed: 19 Nov. 2020.

MOURÃO, Arnaldo Prata. Tomografia computadorizada: tecnologias e aplicações. Difusão Editora, 2018.

NIST—National Institute of Standards and Technology. Available at: < https://www.nist.gov/national-institute-standards-and-technology > Last accessed: 19 Jan. 2020.

DALMAZO, J. et al. Radiation dose optimization in routine computed tomography: a study of feasibility in a University Hospital. Radiologia Brasileira, v. 43, p. 241-248, 2010. DOI: https://doi.org/10.1590/S0100-39842010000400008

American Association of Physicists in Medicine. AAPM position statement on the use of bismuth shielding for the purpose of dose reduction in CT scanning. AAPM website., 2012. Available at: <https://www.aapm.org/publicgeneral/bismuthshielding.pdf>. Last accessed: 19 Nov. 2020.

HAMADA, Nobuyuki. Ionizing radiation sensitivity of the ocular lens and its dose rate dependence. International Journal of Radiation Biology, v. 93, n. 10, p. 1024-1034, 2017. DOI: https://doi.org/10.1080/09553002.2016.1266407

Downloads

Published

2022-09-18

How to Cite

Fernandes, L. C., & Prata Mourão, A. (2022). Dose reduction evaluation in radiosensitive tissues for head CT scans using two phantoms and bismuth eye shielding. Brazilian Journal of Radiation Sciences, 10(3). https://doi.org/10.15392/bjrs.v10i3.2040

Issue

Section

Articles

Most read articles by the same author(s)