Effects of bismuth breast shielding on dual-energy computed tomography : an experimental phantom study

Abstract

PURPOSE: The purpose of this study is to evaluate the effects of bismuth breast shielding on iodine quantification and radiation exposure in dual-energy computed tomography (DECT).

MATERIALS AND METHODS: Ethics approval was not required for this phantom study. Small balloons were filled with mixtures of water and iodinated contrast (0.2%, 0.6% and 1.0%) to mimic lung nodules. The balloons were located at the anterior and posterior aspects of both lungs in the phantom. DECT was performed with and without breast shielding. Afterwards, iodine overlay attenuation values were measured for each nodule on the iodine maps. Absorbed radiation doses were also measured at the breast. A total of 12 pairs of data from DECT performed with and without breast shielding were obtained for iodine overlay attenuation values of the nodules in each location for each concentration and for radiation doses. Results were compared using the Wilcoxon signed-rank test.

RESULTS: Iodine overlay attenuation values for the 0.2%, 0.6% and 1.0% nodules significantly decreased after breast shielding at the anterior location (P = 0.002 for all). Values significantly decreased after breast shielding at the posterior location for the 0.2%, 0.6% and 1.0% nodules as well (P = 0.002 for all). Absorbed radiation doses to the breast significantly decreased after breast shielding with a reduction rate of 14.8% (P = 0.005)

CONCLUSION: Although the bismuth breast shield can decrease radiation exposure to the breast during DECT, it can significantly affect the results of iodine