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Harvard Medical School
The ventilation-perfusion scan is a nuclear scan so named because it studies both airflow (ventilation) and blood flow (perfusion) in the lungs. The initials V-Q are used in mathematical equations that calculate airflow and blood flow. The test is used primarily to help diagnose a blood clot in the lungs, called a pulmonary embolus.
Today, ventilation-perfusion scans are rarely performed because a chest CT scan is a much more accurate diagnostic test for detecting a pulmonary embolus.