Pulmonary imaging in pregnancy. Maternal risk and fetal dosimetry

A Tc-99m macroaggregated albumin (MAA) perfusion lung scan and a Tc-99m DTPA aerosol ventilation scan were performed for suspicion of pulmonary embolism (PE) in a patient who was ten weeks pregnant. There was considerable reluctance on the part of the obstetricians to permit this study. Standard MIRD dose estimates to the fetus were performed, which showed a maximum fetal exposure of about 50 mrem. It was concluded that the risk to mother and fetus from undiagnosed and untreated PE is much greater than the negligible risk to the fetus from the radiation exposure; fear of fetal radiation damage should not be a deterrent to performing these scans.