 As Q in physiology is the letter used to describe bloodflow the term V/Q scan emerged.This test is most commonly done in order to check for the presence of a blood clot or abnormal blood flow inside the lungs (such as a pulmonary embolism (PE) although computed tomography with radiocontrast is now more commonly used for this purpose.The V/Q scan may be used in some circumstances where radiocontrast would be inappropriate, as in kidney failure.