Journal of Isfahan Medical School

Journal of Isfahan Medical School

Dose Assessment in Multidetector Computed Tomography (CT) of Polymethylmethacrylate (PMMA) Phantom Using American Association of Physicists in Medicine-Task Group Report No. 111 (AAPM-TG111)

Document Type : Original Article (s)

Authors
Soheila Sharifian 1
Daryoush Shahbazi-Gahrouei 2
1 MSc Student, Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
2 Professor, Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
Abstract
Background: Computed tomography (CT) is one of the most used imaging modalities and is one of the main sources of population exposure. Recently, patient doses are estimated through CT dose index (CTDI) phantoms as a reference to calculate CTDI volume (CTDIvol) values followed by calculating equilibrium dose (Deq). This study aimed to improve measurement methods for equilibrium dose and the effective dose using the American Association of Physicists in Medicine-Task Group Report No. 111 (AAPM-TG111).Methods: Using standard phantom of polymethylmethacrylate (PMMA) and pencil ionization chamber, the values of CTDI100 and ε(CTDI100), and DL(0) were calculated followed by calculating equilibrium dose, hence obtaining the total effective dose.Findings: The average equilibrium dose in according to the CTDI100 and CTDIvol was found to be 26.11 and 58.99, respectively; which was based on the value of 19.4 and 42.4 mGy recorded by CT console. Differences between CTDIvol and Deq were 34.58% and 39.12% based on the experiments setting up by the CT-weighted and volume dose index, respectively.Conclusion: Differences between values of CTDIvol and Deq were consistent with the literature results. Overall, weighted dose index of CT systems is not sufficient to determine patient’s dose and using new recommended indices are required.
Keywords
Multidetector computed tomography
Radiation Dosage
Polymethylmethacrylate (PMMA)
Radiologic phantom
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Journal of Isfahan Medical School
Volume 35, Issue 421 - Serial Number 421
January and February 2017
Pages 200-205

  • Receive Date 31 December 2016
  • Accept Date 06 April 2022