Original Article

Assess the difference between Computed Tomography Dose Index and equilibrium dose using a standard phantom

Abstract

Abstract

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 scanners 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 dose displayed in the volume computed tomography dose index (CTDIvol) at the end of each exam. Eventually, the effective dose was calculated for both methods.

Material and Methods: Using standard phantom of polymethylmethacrylate (PMMA) and pencil ionization chamber, the values of CTDI100, ( CTD100), CTDIvol, cumulative dose, equilibrium dose, and effective dose were calculated.

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 26% to 35%.

Conclusion: the CTDIVol is not suitable to evaluate the radiation dose at the end of each scan and the use of an equilibrium dose for dosimetry of new systems is recommended.

Keywords: Multidetector computed tomography, Equilibrium dose, Computed tomography volume dose index, AAPM-TG 111, Radiation dosimetry

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Keywords
Multidetector computed tomography Equilibrium dose Computed tomography volume dose index AAPM-TG 111 Radiation dosimetry
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1.
Sharifian Jazi S, Dalvand S, Zamani H, Hossein Beigi F, Ghaderian M, Faraji R, Shahbazi-Gahrouei DS-G. Assess the difference between Computed Tomography Dose Index and equilibrium dose using a standard phantom. Frontiers Biomed Technol. 2025;.