Lung Perfusion Scan

**Semantic type:** Diagnostic Procedure

**Definition:** A scan, whereby a radioactive tracer substance is injected into a vein in the arm, to highlight areas of the lungs that are not receiving enough blood. The tracer is absorbed evenly in areas of the lung where the blood flow is normal and these areas show up with the tracer distributed evenly. Areas that are not receiving enough blood show up as cold spots.