Tehran University of Medical Sciences Frontiers in Biomedical Technologies 2345-5837 13 2 2026 05 01 439 446 Soheyla Sharifian Jazi Department of Medical Physics, School of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran Saman Dalvand Department of Medical Physics, School of Medical Sciences, Tarbiat Modares University Hamed Zamani Department of Medical Physics, School of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran Fahimeh Hossein Beigi 0000-0002-8113-3475 Mohammad Ghaderian Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Reihaneh Faraji Department of Medical Physics, Medicine Faculty, Mashhad University of Medical Sciences, Mashhad, Iran Daryoush Shahbazi-Gahrouei Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran 2023 12 14 2024 06 28 Purpose: The dose of Computed Tomography (CT) scan exams consists of a large proportion of all medical imaging modalities' dose burdens. There are different methods to measure and describe radiation in CT. A standardized way is to measure the Computed Tomography Dose Index (CTDI). However, due to the increase in the detector system size along the z-axis in new CT scanner generations, new measurement methods are described in the American Association of Physicists in Medicine-Task Group No.111(AAPM-TG111). This study aims to estimate the equilibrium dose and compare it with the amount displayed in the volume Computed Tomography Dose Index (CTDIvol) at the end of each exam. Eventually, the effective dose was calculated for both methods. Materials and Methods: Using a pencil ionization chamber and standard polymethylmethacrylate (PMMA phantom), the following values were calculated: CTDI100, CTDIvol, cumulative dose, equilibrium dose, and effective dose. Results: Six protocols performed in two centers, and the results indicated that the measurements with a standard CT dosimetry phantom, was varied between average equilibrium dose and CTDIvol, and the discrepancies ranged between 27% to 33%. Conclusion: The CTDIVol is not suitable for evaluating the radiation dose at the end of each scan, and the use of an equilibrium dose for dosimetry of new systems is recommended. https://fbt.tums.ac.ir/index.php/fbt/article/view/901 https://fbt.tums.ac.ir/index.php/fbt/article/download/901/490