Lung Scan

Ventilation and Perfusion Scan

What To Think About

• Checking for a blood clot in your leg (deep venous thrombosis) can help your doctor decide whether you are at high risk of having a pulmonary embolism. After a medical history and physical examination are done to establish your risk level (pretest probability) for deep leg vein thrombosis, an ultrasound is usually done. Your pretest probability and initial ultrasound results will help your doctor determine the most appropriate follow-up tests to evaluate whether you have a pulmonary embolism. For more information, see the medical test Doppler Ultrasound.
• Uncertain perfusion scan results are sometimes investigated further using pulmonary angiography or a newer computed tomography scanning technique called CT pulmonary angiography, or CTPA. Pulmonary angiography is an X-ray test that uses contrast material injected into the bloodstream to evaluate the blood flow through the arteries leading to the lungs (pulmonary arteries). Many medical centers or doctors now use CTPA as their first choice for evaluating a pulmonary embolus rather than a lung scan because CT has become more available and is often more accurate. For more information, see the medical tests Angiogram of the Lung and CT Scan of the Body.
• Lung scan results for people who have a long-term (chronic) lung disease, such as emphysema or chronic obstructive pulmonary disease (COPD), may be difficult to interpret. For this reason, other tests, such as CT angiogram, may be done.
• The results of a combined (ventilation and perfusion) lung scan, often called a V/Q scan, may be difficult to interpret. These results should be interpreted along with a person's symptoms and the results of other tests, such as a physical examination, lab tests, and a chest X-ray.

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Author:	Jan Nissl, RN, BS	Last Updated: November 1, 2006
Medical Review:	Patrice Burgess, MD - Family Medicine Kenneth B. Sutherland, CD, BSc, MD, FRCPC - Diagnostic Radiology
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