Investigation into the effects of lead shielding for fetal dose reduction in CT pulmonary angiography.

This work aims to determine whether lead shielding can be used to decrease the radiation dose to the fetus during CT scans for the diagnosis of pulmonary embolism during early stage pregnancy. An anthropomorphic phantom was modified to contain a 15 cc ionization chamber at the site of the uterus to enable fetal dose to be measured. The effects of a range of scan parameters, positioning of lead and thicknesses of lead were investigated. Fetal dose was lower with lower values of kV(p) and mAs. An increasing thickness of lead decreased the radiation dose to the uterus, as did increasing the proportion of the patient covered by the lead shielding. Fetal dose increased exponentially as the edge of the scan volume moved closer to the point of measurement. In no experiment was the dose to the fetus increased by the presence of the lead. It was found that the fetal radiation dose from a CT scan following a pulmonary embolism protocol can be effectively reduced by the use of lead shielding.