Investigation of Dose Distributions of Computed Tomography with Cylindrical Polymethyl Methacrylate (PMMA) Phantoms

Document Type : Original Article (s)

Authors

1 Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

2 Professor, Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

3 Assistant Professor, Department of Medical Physics and Medical Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

4 Department of Radiotherapy, Seyedoshohada Hospital, Isfahan, Iran

5 Department of Physics, School of Physics, Isfahan University of Technology, Isfahan, Iran

Abstract

Background: This study aimed to investigate the effect of patient’s size on the distribution and amount of dose of computed tomography (CT) based on standard cylindrical polymethyl methacrylate (PMMA) phantoms.Methods: In this study, a two-dimensional film dosimetry method was represented via using radiographic films; the effect of patient’s size on the distribution and the amount of received dose was investigated using cylindrical phantoms with 10, 16, 24 and 32 cm diameters. The cylindrical phantoms were made of polymethyl methacrylate sheets. By proper calibration, two-dimensional distribution of the dose was measured using film dosimetry in these phantoms in a single axial rotation.Findings: The dose distribution in the cylindrical phantoms was not symmetric particularly in closer points to the surface. The received dose in the cross-section of phantom increased with beam width. The received dose in the central part of phantom decreased more than its surface by the increment of phantom diameter. Specially, using a cylindrical phantom with diameter of16 cm, the received dose in the central part of the phantom decreased to 65% of its surface dose; whereas this percentage for cylindrical phantoms with diameters of 24 and 32 cm was 45% and 35%, respectively.Conclusion: The dose distribution in the cross-section of the pediatric patients is more uniform. It is highly dependent on the couch attenuation and overscan, leading to asymmetry of the dose distribution. The received dose in the pediatric patients would be more than adults for the same mAs.

Keywords

References

  1. Boone JM, Strauss KJ, Cody DD, Maccolough C, Mcnitt-Gray MF. Size-specific dose estimates (SSDE) in pediatric and adult body CT examinations. Report of AAPM Task Group 204. College Park, MD: American Association of Physicists in Medicine; 2011.
  2. Bogdanich W. Radiation overdoses point up dangers of CT scans. The New York Times 2009 Oct 16; A13.
  3. United State Food and Drug Administration. White paper: Initiative to reduce unnecessary radiation exposure from medical imaging [Online]. [cited 2010 Dec 14]; Available from: URL: http://www.fda.gov/Radiation-EmittingProducts/RadiationSafety/RadiationDoseReduction/ucm199994.htm
  4. Mettler FA, Wiest PW, Locken JA, Kelsey ChA. CT scanning: patterns of use and dose. J Radiol Prot 2000; 20(4): 353.
  5. Committee on the Biological Effects of Ionizing Radiation. Health effects of exposure to low levels of ionizing radiation: BEIR V. Washington, DC: National Academy Press; 1990.
  6. McCollough C, Cody D, Edyvean S, Geise R, Gould B, Keat N, et al. The measurement, reporting, and management of radiation dose in CT. Report of AAPM Task Group 23. College Park, MD: American Association of Physicists in Medicine; 2008. p. 1-28.
  7. Shope TB, Gagne RM, Johnson GC. A method for describing the doses delivered by transmission x-ray computed tomography. Med Phys 1981; 8(4): 488-95.
  8. Brady S, Yoshizumi T, Toncheva G, Frus D. Implementation of radiochromic film dosimetry protocol for volumetric dose assessments to various organs during diagnostic CT procedures. Med Phys 2010; 37(9): 4782-92.
  9. Lampinen JS. Calculating patient specific doses in X-ray diagnostics and from radiopharmaceuticals. Helsinki, Finland: University of Helsinki; 2000.
  10. Alm-Carlsson G, Dance D, DeWerd L, Kramer H, Ng K, Pernicka F, et al. Dosimetry in diagnostic radiology: an international code of practice. Technical Reports Series No. 457. Vienna, Austria: International Atomic Energy Agency; 2007.
  11. Haus AG. Advances in film processing systems technology and quality control in medical imaging. Madison, WI: Medical Physics Pub Corp; 2001
  12. Haba T, Koyama S, Ida Y. Influence of difference in cross-sectional dose profile in a CTDI phantom on X-ray CT dose estimation: a Monte Carlo study. Radiol Phys Technol 2014; 7(1): 133-40.
  13. Fearon T, Xie H, Cheng JY, Ning H, Zhuge Y, Miller RW. Patient-specific CT dosimetry calculation: a feasibility study. J Appl Clin Med Phys 2011; 12(4): 3589.
Journal of Isfahan Medical School
Volume 32, Issue 309 - Serial Number 309
September and October 2015
Pages 1918-1932

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History

  • Receive Date: 06 December 2014
  • Revise Date: 28 May 2024
  • Accept Date: 06 April 2022

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