Automatic Exposure Control systems and current modulations: comparison of different 64-slice CT scanners

Aim of this study is to compare four CT devices as regards the current modulation supplied by their Automatic Exposure Control (AEC) systems. How the current modulation is influenced by the presence of contrast medium (injected in vena after basal phase images acquisition or given per os) and of high atomic number materials (for example: surgical clips) is also under study. The considered scanners and the implemented AEC systems are: GE Light Speed VCT (AutomA and SmartmA), Philips Brilliance 64 (Dose Right ACS and DDOM), Siemens Somatom Sensation 64 (CARE Dose 4D) and Toshiba Aquilion 64 (Sure Exposure). Abdomen standard protocols have been investigated. The CT examinations of ten adult standard patients have been considered. Investigated CT devices show that the implementation by AEC systems of different technical approaches leads to different current modulation curves. The presence of contrast medium injected in vena after basal phase image acquisition does not modify significantly current modulation. In some cases, the presence of contrast medium given per os and of high atomic number materials could effectively affect current modulation.