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)

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. © 2017, Isfahan University of Medical Sciences(IUMS). All rights reserved.