Imaging in pregnancy
-Quick review to boost your facts
Imaging is important for the diagnosis of acute and chronic conditions. However, The debate over the safety of imaging modalities for pregnant women can result in avoidance of useful diagnostic tests in pregnancy and the potential for delayed diagnosis. This article summarises the benefits and risks of various imaging techniques in pregnancy and highlights appropriate techniques for women presenting with common medical symptoms to healthcare professionals.
What are the risks?
-Ionising radiation can have stochastic effects (those which occur by chance) or deterministic effects on the fetus
-Deterministic effects are predictable based on threshold doses of radiation. They can include fetal malformation, fetal growth restriction and neurological effects. Importantly, it is estimated that these effects will only occur at fetal radiation doses greater than 50 mGy.
What is the fetal exposure in common investigations?
-Cervical spine X-ray (AP and lateral views): <0.001 mGy
-Chest X-ray (two views): ≤0.01 mGy
-Abdominal X-ray: 0.1–3.0 mGy
-Pelvic CT scan: 10–50 mGy
Other imaging modalities
-Potential negative effects may be thermal or mechanical, relating to increased tissue temperature or bubbles of gas forming in tissues, respectively.
-Overall, it is thought that there are no significant negative effects of ultrasound when exposure is limited to <60 minutes.
Nuclear medicine imaging
-Nuclear studies – including pulmonary ventilation/perfusion (VQ) scans – are useful to determine organ function by using a radioisotope. In general, fetal radiation exposure from V/Q scans is <5 mGy
-Positron emission tomography (PET) scanning may be necessary for imaging of malignancy during pregnancy. The most commonly used radiotracer in PET scanning is F-FDG
-Data indicate that PET scanning with F-FDG should not be withheld for fear of excessive radiation exposure. Headache Breast mass Calf pain / leg swelling Abdominal pain Shortness of breath Imaging women
Remember...Safety of imaging in pregnancy is improved by careful history taking and examination and clear identification of the clinical question to be answered and the timeframe in which it should be investigated. Seek advice from a senior radiologist regarding the most suitable imaging modality, and provide appropriate counseling of women.