Abstract
Objective: Our aim was to evaluate image quality and radiation dose of screening CT colonography (CTC) conducted by the fixed tube current technique or that using an automatic tube current modulation system.
Subjects and Methods: Screening CTC at 3 fixed tube current settings (group A,50 mAs; group B,75 mAs; and group C,100 mAs) and that with an automatic tube current modulation system (group D, Volume EC SD20) using a 64-channel MDCT scanner were performed on 836 asymptomatic individuals. In addition, all groups were divided into 4 subgroups based on differences in body mass index (BMI). The mean radiation dose of each group was determined using the dose-length product. Image quality was evaluated by 3 independent reviewers.
Results: The mean radiation dose was 10.7 mSv for group A, 16.0 mSv for group B, 20.7 mSv for group C, and 5.4 mSv for group D. Thus, the radiation dose was lower in the group scanned using the automatic tube current modulation system (Volume EC SD20) than in the groups scanned by the fixed tube current technique (50 mAs, 75 mAs, or 100 mAs). The overall radiation dose increased as BMI increased, especially in group D. All subjects in all groups had acceptable image quality.
Conclusions: The results of this study show that the radiation dose during CTC can be reduced by an automatic tube current modulation system while maintaining diagnostic image quality. An appropriate automatic tube current modulation system is therefore useful for screening CTC.
