Is a Ventilation Study Really Necessary when Performing Lung Scans on Pregnant Patients?*
Lung imaging on pregnant women posses a concern due to the radiation dose received to the conceptus. There is no consensus as to whether both ventilation and perfusion (v/q) scans are needed or perfusion only scanning is sufficient to diagnose Pulmonary Embolism (PE) in these patients. An audit was performed over a 3 year period, of all pregnant patients who had lung scans at the Lyell McEwin Hospital (LMH). 35 patients underwent scanning (mean age = 21 years, mean gestation period = 21 weeks). 11 patients had perfusion only studies while 24 had v/q scans. 24 of the 35 patients had prior chest X-rays; only one was abnormal. Only 3 lung scans were classified as intermediate or high probability for the diagnosis of PE (one intermediate result was a perfusion-only study in a patient with an abnormal chest X-ray).
In general the fetal dose from lung scanning is minimal compared to the accepted cumulative dose recommended by the International Commission of Radiological Protection (ICRP) of 50mGy. However the results of our audit imply that there is no need to perform a ventilation study, if there is no history of respiratory disease, or if the chest X-Ray is normal. Also by performing a perfusion only study the MAA dose is reduced as well as the fetal dose by up to 65%.
Our conclusion from this audit is that routine ventilation imaging in pregnant patients is not necessary, resulting in a reduction in radiation exposure and anxiety to the patient and fetus.