SU‐F‐I‐06: Evaluation of Imaging Dose for Modulation Layer Based Dual Energy Cone‐Beam CT

Abstract

Purpose:Dual energy cone beam CT system is finding a variety of promising applications in diagnostic CT, both in imaging of endogenous materials and exogenous materials across a range of body sites. Dual energy cone beam CT system to suggest in this study acquire image by rotating 360 degree with half of the X‐ray window covered using copper modulation layer. In the region that covered by modulation layer absorb the low energy X‐ray by modulation layer. Relative high energy X‐ray passes through the layer and contributes to image reconstruction. Dose evaluation should be carried out in order to utilize such an imaging acquirement technology for clinical use.Methods:For evaluating imaging dose of modulation layer based dual energy cone beam CT system, Prototype cone beam CT that configured X‐ray tube (D054SB, Toshiba, Japan) and detector (PaxScan 2520V, Varian Medical Systems, Palo Alto, CA) is used. A range of 0.5–2.0 mm thickness of modulation layer is implemented in Monte Carlo simulation (MCNPX, ver. 2.6.0, Los Alamos National Laboratory, USA) with half of X‐ray window covered. In‐house phantom using in this study that has 3 cylindrical phantoms configured water, Teflon air with PMMA covered for verifying the comparability the various material in human body and is implemented in Monte Carlo simulation. The actual dose with 2.0 mm copper covered half of X‐ray window is measured using Gafchromic EBT3 film with 5.0 mm bolus for compared with simulative dose.Results:Dose in phantom reduced 33% by copper modulation layer of 2.0 mm. Scattering dose occurred in modulation layer by Compton scattering effect is 0.04% of overall dose.Conclusion:Modulation layer of that based dual energy cone beam CT has not influence on unnecessary scatter dose.This study was supported by the Radiation Safety Research Programs (1305033) through the Nuclear Safety and Security Commission.