Effective doses in angiography and interventional radiology: calculation of conversion coefficients for angiography of the lower limbs.

The present study reports on investigations that we have performed to allow the calculation of effective doses (E) in interventional radiology. The use of published conversion tables might not allow sufficient guidance for the establishment of optimization strategies for procedures in interventional radiology. With the Monte Carlo N-Particle transport code (MCNP4B), conversion coefficients, linking dose-area product (DAP) measurements with E, are calculated for angiography of the lower limbs in six hospitals. The influence of various parameters on the calculation of these conversion coefficients is studied in a systematic way using the 2(n) factorial design. In this design the effect of different parameters and their pair-wise interactions on a certain variable is explored. In our study, the relevant parameters are tube potential, total filtration and field size and position. We concluded that the influence of radiation spectrum (kVp + filtration) is large and that the effect of field position and size is moderate, except when differences are observed in respect of the gonads. In that case, the variation in conversion coefficients is large. The results of this statistical analysis are then applied to the differences observed between the conversion coefficients, calculated for angiography of the lower limbs in the six hospitals. Recommendations for optimization of patient doses are given.