Risks are essentially the same as for X-rays (radiation) and needle pricks.

There is a small exposure to radiation from the radioisotope. The radioisotopes used during scans are short lived, with almost all radiation gone in a few days. However, as with any radiation exposure, caution is advised during pregnancy or if a woman is breastfeeding. No radiation is emitted from the scanner; it detects radiation and converts it to a visible image.

There is a slight risk for infection or bleeding at the site of the needle insertion. The risk with perfusion scan is no different than for placement of an intravenous needle for any other purpose.

It is extremely rare, but a person may develop an allergy to the radioisotope, which may include a serious anaphylactic reaction.

A pulmonary ventilation and perfusion scan may be a lower-risk alternative to pulmonary angiography for evaluating disorders of the lung blood supply.

This test may not provide an absolute diagnosis, particularly in people with underlying lung disease. Other tests may be necessary to confirm or rule out the findings of a pulmonary ventilation and perfusion scan.