Lung ventilation/perfusion (VQ) scans involve little risk for most people. The radioisotopes used for both tests expose you to a small amount of radiation. The amount of radiation in the gas and injection together are about the same as the amount a person is naturally exposed to in 1 year.
Although rare, the radioisotopes may cause an allergic reaction.
The radiation from a VQ scan leaves your body after a few days. Exposure to radiation is associated with a risk of cancer. However, it's not known whether the amount of radiation from a VQ scan increases your risk for cancer.
You and your doctor will decide whether the benefits of a VQ scan outweigh the possible risks. Your doctor also will try to avoid ordering multiple VQ scans for you over a short period.
If you're pregnant or breastfeeding, talk with your doctor about the risk of radiation to your baby. He or she will consider whether another test can be used instead.
Very rarely, the radioisotopes used in VQ scans can cause an allergic reaction. Hives or a rash may result. Medicines can relieve this reaction.