Dose Considerations and Radiation Protection Issues in Multislice CT

Summary

Results from a recent survey on MSCT practice in Germany indicate that 2-slice scanners (which are mainly former Elscint Twin scanners) are used at dose levels comparable with modern SSCT scanners, while dose values related with 4-slice scanner protocols are currently significantly, but not alarmingly, higher. The main reasons are: (1) reduced slice thickness, which tempts the users to increase the electrical current-time product in order to compensate for increased noise, (2) overbeaming due to penumbral effects, which are most pronounced at narrow slice collimation, and (3) reduced transparency of the implications of parameter settings on dose. The key factor to reduce dose at MSCT systems with N ≥ 4 to a level comparable to modern single-slice and dual-slice scanners is to appreciate the improved detail contrast achieved with thin slices due to reduced partial volume effect. This overcompensates for the drawback of increased noise. Thus, at least the same dose level as for modern SSCT scanners should be attainable. Furthermore, new technical means have the potential for dose reduction. It should be emphasized, however, that technical means are only a prerequisite, but no guarantee for dose reduction. Of greatest importance is appropriate training and guidance of the medical and technical staff operating the MSCT scanner with respect to the specific factors determining patient exposure and its reduction.