 A localized area of decreased uptake, usually in a wedge shaped (or pie shaped) configuration with normal ventilation images (mismatched defect) suggests a pulmonary embolus or blood clot in the lungs, which leads to reduced perfusion beyond the obstruction.Although this test uses radioactive materials, the total amount of radiation exposure is low.Typical effective doses for a V/Q scan range from 1-5 mSv.