V/Q (ventilation/perfusion) scan is an examination of the lung that evaluates pulmonary vasculature perfusion and segmental bronchoalveolar tree ventilation.A VQ scan, also called a Ventilation (V) Perfusion (Q) scan, is made up of two scans that examine air flow and blood flow in your lungs. The first scan measures how well air flows through your lungs (ventilation). The second scan looks at where the blood flows in your lungs (perfusion).