Varying kVp as a means of reducing CT breast dose to pediatric patients

We investigated the possibility of reducing radiation dose to the breast tissue of pediatric females by using multiple tube voltages within a single CT examination. The peak kilovoltage (kVp) was adjusted when the x-ray beam was directly exposing the representative breast tissue of a 5-year-old, 10-year-old, and an adult female anthropomorphic phantom; this strategy was called kVp splitting and was emulated by using a different kVp over the anterior and posterior tube angles. Dose savings from kVp splitting were calculated relative to using a fixed kVp over all tube angles and the results indicated savings in all three phantoms when using 80 kVp over the posterior tube angles regardless of the anterior kVp. Monte Carlo (MC) simulations with and without kVp splitting were performed to estimate absorbed breast dose in voxelized models constructed from the CT images of pediatric female patients; 80 kVp was used over the posterior tube angles. The MC simulations revealed breast dose savings of between 9.8% and 33% from using kVp splitting compared to simulations using a fixed kVp protocol with the anterior technique. Before this strategy could be implemented clinically, the development of suitable image reconstruction algorithms and the image quality of scans with kVp splitting would need further study. (paper)