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

Background: Although the bismuth breast shield can reduce radiation exposure to the breast during dual-energy computed tomography (DECT), it can potentially affect material quantification on DECT due to artifacts. Purpose: To evaluate the effects of bismuth breast shielding on iodine quantification and radiation exposure in DECT. Material and Methods: Small balloons were made with 0.2%, 0.6% and 1.0% blended iodinated contrast (370 mg/mL of iodine) with water. The balloons were located at both anterior and posterior lungs in an adult anthropomorphic chest phantom. DECT was performed with and without breast shielding. Afterwards, iodine concentration values were measured for each balloon on the iodine maps. Absorbed radiation doses in the breast were measured with the optically stimulated luminescence dosimeter. Results: After shielding, we obtained significantly decreased iodine quantification for all three concentrations with 0.78 +/- 0.13 to 0.46 +/- 0.13 mg/mL, 2.31 +/- 0.17 to 1.68 +/- 0.19 mg/mL, and 3.82 +/- 0.10 to 2.84 +/- 0.20 mg/mL at the anterior location, and 0.72 +/- 0.11 to 0.48 +/- 0.09 mg/mL, 2.24 +/- 0.13 to 1.87 +/- 0.21 mg/mL, and 3.75 +/- 0.16 to 3.15 +/- 0.14 mg/mL at the posterior location for the 0.2%, 0.6%, and 1.0% balloons, respectively (P = 0.001 for all). After shielding, absorbed radiation doses to the breast significantly decreased by 14.8% (4.32 +/- 0.33 to 3.68 +/- 0.30 mGy; P= 0.005). Conclusion: Although using the bismuth breast shield may decrease radiation exposure to the breast on DECT, it may also significantly affect iodine quantification.