What are the normal findings on a ventilation perfusion scan?
A normal V/Q scan consists of uniform ventilation throughout both lung fields. On a 133 Xe ventilation scan, there is usually good inflow of the gas, uniform radiotracer activity in the lungs during the equilibrium phase that lasts approximately 3 minutes as the patient breathes into the closed system of the machine, and then rapid and uniform washout from the lungs within about 1 to 2 minutes. No radiotracer activity should be observed in the brain, because this would imply the presence of a right-to-left shunt. On the 99m Tc-MAA perfusion scan obtained in the supine position, uniform radiotracer uptake is seen throughout the lungs.
Causes of Gas Trapping on a ventilation perfusion scan
- • Asthma
- • COPD
- • Chronic bronchitis
- • Mucous plug
- • Cystic fibrosis
- • Smoke inhalation
- • Airways-obstructive tumor
- • Airways-obstructive foreign body