Radiation dose comparison of photon-counting breast CT and mammography: A phantom study.

Background: Spiral breast CT (BCT) systems operate without breast compression while providing more comprehensive three-dimensional information than digital mammography (DM) and digital breast tomosynthesis (DBT). However, before BCT systems can be considered as part of screening programs for breast cancer, concerns about dose exposure in a diagnostic setting (which is generally higher in CT systems) must be addressed. Methods: This work compares dose measurements between mammography and breast CT with commercial devices and clinical protocols. 3D-printed phantoms of three different sizes were filled with four mixtures simulating different breast densities. Calibrated MOSFET dosimeters measured the entrance surface dose (ESD); in Saddition, a Monte Carlo simulation was performed, matched to the measurements, and used to calculate the average absorbed dose (AAD). Results: The entrance dose for DM + DBT is always higher than for BCT, up four times for the largest and densier phantom, corresponding to 74% reduction in the ESD for BCT. The results for the AAD vary widely depending on size and density. In the lowest density phantom the dose with BCT is generally higher than with a standard diagnostic mammography protocol (up to +227% increase for the small phantom). However, in case of the highest density, BCT achieved a dose reduction compared to the mammography protocol (-14% for the medium phantom and -15% for the large phantom). Conclusions: BCT consistently reduced entrance surface dose compared to the combination of one DM and one DBT, while the average absorbed dose was higher for most phantom configurations.