Lead shielding in pediatric chest CT: Effect of apron placement outside the scan volume on radiation dose reduction

OBJECTIVE. The purpose of this study was to quantify the dose reduction resulting from the use of lead aprons for pediatric chest CT as a function of the distance between the apron and the bottom of the scan range. MATERIALS AND METHODS. Semianthropomorphic phantoms of the head, abdomen, and pelvis were placed adjacent to a chest phantom to mimic the habitus of a 5-year-old child. A chest CT scan was performed, and a point dosimeter was used to measure the radiation dose at points within and outside the scan range. A lead apron was placed 1, 5, and 10 cm from the bottom of the CT scan range, and the measurements were repeated. The weightedaverage dose was calculated for each measurement position. RESULTS. The weighted-average dose within and outside the scan range was 1.7 and 0.067 mGy, respectively. The mean (percentage) dose reduction outside the scan range resulting from use of the lead apron was 0.013 mGy (19.1%), 0.007 mGy (10.1%), and 0.003 mGy (4.3%) when the lead apron was placed at distances of 1, 5, and 10 cm from the bottom of the scan range, respectively. The corresponding total percentage dose reduction (including the dose from the primary scan) was 0.7%, 0.4%, and 0.2%, respectively. CONCLUSION. As the lead apron was placed farther from the scan range, the amount of dose reduction diminished. The reduction in dose was extremely small compared with the overall dose from the examination. The small dose reduction gained from the use of lead shielding over the abdomen and pelvis during chest CT examination of pediatric patients may not outweigh the associated potential risks of artifacts and infection.