A lung perfusion scan is used to evaluate blood flow to the lungs and is often done with a lung ventilation scan. A radioactive tracer is injected into the patient, and an imaging machine takes images to identify areas where blood supply is inadequate. Risks are low, but patients with allergies or adverse reactions should notify their care providers.
A lung perfusion scan is a medical imaging scan conducted to evaluate the quality of blood flow to the lungs. It is usually done in conjunction with a lung ventilation scan, looking at how much air is entering the lungs, and the two tests may be known together as a V/Q scan. The purpose of these scans is to look for areas where blood or air is not circulating within the lungs, indicating the presence of a pulmonary embolism or other breathing problems. Testing is done on an outpatient basis in an imaging clinic or hospital.
For a lung perfusion scan, a small amount of short-lived radioactive tracer material is injected into the patient. The patient lies flat and still on a table, and an imaging machine takes a series of images to follow the tracer as it flows through the blood into the lungs. Cold spots on the scan indicate areas where the blood supply is inadequate, indicative of a lung problem. Once the scan is performed, the patient can usually go home immediately and the tracer will naturally clear from the body over the course of several days.
In a V/Q test, a scan of the ventilation is performed first, with the patient inhaling a mixture of oxygen and radioactive gas. Once the patient’s lungs are cleared, a lung perfusion scan can be performed. The results of both scans are compared and should be identical, showing healthy blood perfusion to the lungs and full circulation of oxygen. Cold spots on scans are a cause for concern. Additionally, an X-ray of the lungs may be taken to use as a basis for comparison and study, depending on why the patient takes the scans in the first place.
The risks associated with a lung perfusion scan are low. The radioactive isotope is supplied in a very small dosage and should not expose the patient to the risk of disease or other complications. Injection site infections are a potential but very small risk, provided hospital staff use safe injection technique. In some cases, patients develop allergies to the tracer dyes used, in which case they may be at risk of an allergic reaction in future scans. People with a history of adverse reactions during medical imaging studies with radioactive substances and people with egg allergies should notify their care providers before a lung perfusion scan.
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