Shielding Anatomy Outside of the Direct Radiation Beam: Appropriate Practice or More Harm than Good?
AffiliationThe University of Arizona College of Medicine - Phoenix
MetadataShow full item record
PublisherThe University of Arizona.
DescriptionA Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.
AbstractIntroduction/Background: Lead shields have been used for decades to reassure patients and clinicians that radiosensitive areas (e.g., gonads, thyroid) are protected during radiography. Despite this common practice, supporting data have been limited and conflicting. Further examination of this practice is warranted to improve patient safety. The purpose of this study was to measure the effect of a pelvic lead shield on radiation dose during a chest radiograph. Methods: For 50 consecutive pediatric chest radiographs, 2 nanoDot™ dosimeters were affixed to either side of the pelvic lead shield, which was placed according to existing protocols. After the exam, dosimeters were labeled with the position (in front of or behind the shield) and a patient identifier. Radiation doses from the dosimeters were measured and recorded along with the patient’s age, gender, weight, exam type (anteroposterior or posteroanterior), and technologist identifier. For a small subset of the exams, the mA and kVp were recorded. Results: The median radiation dose measured in the front of the shield was 33.7 mrad, while the median radiation dose measured behind the shield was 33.4 mrad. The median absolute dose reduction demonstrated a statistically significant decrease of 1.01 mrad (p=0.02) behind the shield, with an interquartile range of -0.93 to 2.79 mrad. The trend did not significantly vary by technologist. There were no statistically significant trends based on patient age, weight, weight percentile for age, exam type, mA, or kVp. Discussion/Conclusion: Using a pelvic shield results in a statistically significant reduction in radiation dose behind the shield during chest radiography. However, the median dose reduction of 1.01 mrad was 3% of the total median dose and is equivalent to 1 day of natural background radiation exposure. Therefore, the difference in radiation dose in front of and behind the lead shield may be statistically but not clinically significant. Additionally, the variation between exams was large, with approximately 1/3 of the exams recording an increased dose behind the lead shield. The long-held assumption that lead shielding provides marked radiation dose reduction should be reconsidered, as the effective dose difference may be negligible and not clinically