Estimating effective dose from 3D imaging with interventional fluoroscopy systems using limited exposure data

Abstract

Background Estimations of the effective dose from three-dimensional (3D) rotational imaging with interventional fluoroscopy systems are hampered by the fact that not all systems provide individual exposure values for each projection image included in the examination. Purpose To investigate the error in resulting effective dose introduced by not using individual exposure values for each projection image in the dose calculations for 3D rotational imaging with interventional fluoroscopy systems. Material and Methods An interventional fluoroscopy system was used to acquire images of two anthropomorphic phantoms. Calculations of the effective dose were performed using two different methods: 1, using individual exposure values for each projection image; and 2, using the mean tube voltage and the total dose-area product (DAP), evenly distributed over a selection of projection images. The second method was also tested in hypothetical examinations to investigate the effects of worst-case scenarios regarding the effect of exposure asymmetry on the error. Results The error in resulting effective dose obtained when simplifying the dose calculations by using Method 2 instead of Method 1 was within ±14%. The error increased slightly for the worst-case scenarios but was still smaller than ±20%, regardless of anatomical region, tube voltage variation, and patient size. Conclusion Given the uncertainties associated with the effective dose concept as well as of reported DAP values, the present study indicates that dose calculations based on average exposure values distributed over a smaller selection of projection angles can provide reasonably accurate estimations of the radiation doses from 3D imaging using interventional fluoroscopy systems.