If a patient is pregnant, which phase of the lung scan is typically performed first?

In the context of lung scans, specifically for patients who are pregnant, the perfusion phase is typically performed first. This choice is based on the understanding that when assessing lung function and blood flow, particularly in pregnant patients, the safety of the fetus is of utmost concern.

The perfusion scan uses a radiopharmaceutical that can be administered while considering its effects on the developing fetus. By performing the perfusion scan first, healthcare providers can gather critical information about blood flow in the lungs without increasing radiation exposure from additional procedures that might be less safe during pregnancy.

Ventilation scans, in contrast, involve inhalation of a radioactive gas or aerosol, which could pose a higher risk to the fetus compared to the injected radiopharmaceutical used for perfusion imaging. Tomography and imaging refer to the broader techniques that may not specifically address the concerns related to blood flow in the lung during pregnancy. Hence, performing the perfusion scan first reflects a prudent approach to minimizing risks while obtaining necessary diagnostic information.