Preparing for VQ scan
Informed by recognized medical guidance
Overview
A VQ scan, short for ventilation-perfusion scan, is a test that looks at how well air and blood flow through your lungs. It uses a tiny amount of a radioactive substance (called a tracer) to create pictures. The test has two parts: one to see how air moves in and out of your lungs (ventilation), and another to see how blood flows through the tiny vessels in your lungs (perfusion). This helps doctors find blood clots in the lungs, called pulmonary embolism.
Key facts
- The scan uses a very low amount of radiation, similar to a chest X-ray.
- You will be asked to breathe in a special gas (ventilation) and then receive an injection (perfusion).
- The procedure is painless and usually takes about 30 to 45 minutes.
Yes, VQ scans are commonly done when doctors suspect a blood clot in the lungs. It is a safe and well-established test.
It is often recommended for people who have sudden shortness of breath, chest pain, or an unexplained drop in oxygen levels. It may also be used for people who cannot have a CT scan due to kidney problems or contrast dye allergy.
Symptoms
- Sudden difficulty breathing or not being able to catch your breath
- Chest pain that is crushing or squeezing
- Coughing up large amounts of blood
- Feeling like you might pass out or lose consciousness
- ⚠Unexplained chest pain that is getting worse
- ⚠Shortness of breath that does not go away with rest
- ⚠Swelling or pain in one leg (may be a sign of a blood clot that could move to the lungs)
Common symptoms
- Sudden shortness of breath for no clear reason
- Sharp chest pain that gets worse when you breathe deeply
- Coughing up blood (even a small amount)
- Rapid heart rate or feeling lightheaded
Symptoms in children
- Children may have trouble describing their symptoms. Look for unusual tiredness, fast breathing, or pale skin.
Symptoms in older adults
- Older adults might have less obvious symptoms like confusion, general weakness, or fainting.
Causes
Main causes
- Blood clots that form in the legs (deep vein thrombosis) and travel to the lungs
- Injury or surgery that causes a blood clot to form
- Prolonged immobility, such as long bed rest or long flights
Risk factors
- Having had a blood clot before
- Cancer or cancer treatment
- Obesity
- Smoking
- Hormonal therapies like birth control pills or hormone replacement therapy
- Pregnancy or recent childbirth
When to see a doctor
See a doctor urgently if:
- If you have sudden chest pain or difficulty breathing, call your local emergency number immediately.
Book a routine appointment if:
- If you have symptoms like unexplained shortness of breath or chest discomfort that keeps coming and going
- If you have a leg that is swollen, warm, or painful (possible deep vein thrombosis)
Diagnosis
The VQ scan is one of the main tests used to diagnose pulmonary embolism. Your doctor will also take your medical history, do a physical exam, and may order blood tests (like D-dimer) or an ultrasound of your legs.
Tests that may be done
- Ventilation scan – you breathe in a harmless radioactive gas while a camera takes pictures
- Perfusion scan – you receive a small injection of radioactive tracer into a vein, and again pictures are taken
- Chest X-ray – sometimes done first to rule out other problems
What to expect at your appointment
You will lie on a table while a special camera moves close to your chest. For the ventilation part, you will breathe through a mask. For the perfusion part, you will get a small injection. The staff will guide you through each step. You can breathe normally. After the test, the radioactive tracer leaves your body naturally within a few hours.
Treatment
If a VQ scan shows a blood clot, treatment aims to stop the clot from getting bigger and prevent new clots. Treatment usually involves blood thinning medication (anticoagulants) taken by mouth or as injections. The length of treatment depends on the cause and your health.
Self-care at home
- Follow your doctor’s advice about taking medication exactly as prescribed
- Stay active but avoid strenuous activities until your doctor says it is safe
- Wear compression stockings if recommended for leg swelling
Medical treatments
Blood thinners (anticoagulants) are the mainstay. They help prevent existing clots from growing and new clots from forming. In some cases, stronger medications called clot-busters (thrombolytics) may be given through a vein for large clots that cause severe symptoms. Treatment is tailored to your individual health.
When is surgery considered?
Surgery is rarely needed. In life-threatening cases, a procedure called embolectomy may be done to remove the clot directly from the lung arteries. This is only for emergencies.
Living with this condition
If you have had a blood clot, you will need to take blood thinners for at least 3 to 6 months. You may need regular blood tests to check how well your blood is thinning. It is important to avoid injury and report any unusual bleeding to your doctor.
Lifestyle tips
- Take your medications exactly as prescribed
- Stay active with gentle exercise like walking
- Wear a medical alert bracelet or carry a card that says you are on blood thinners
Diet and exercise
Eat a balanced diet rich in fruits and vegetables. Be consistent with foods high in vitamin K (like leafy greens) if you are on certain blood thinners – your doctor will tell you if this matters. Avoid alcohol in excess. Start with light activities and gradually increase as you feel able.
Mental health and emotional wellbeing
Having a blood clot can be frightening. It is normal to feel anxious about another episode. Talk to your doctor or a mental health professional if these feelings persist. Support groups can also help.
Prevention
You can lower your risk by staying active, keeping a healthy weight, not smoking, and moving your legs during long trips. If you are at high risk, your doctor may recommend blood thinners as a preventive measure.
Screening programmes
No routine screening is recommended for the general public. If you have a family history of blood clots or other risk factors, talk to your doctor about your personal risk.
Complications
If left untreated
- A pulmonary embolism can be life-threatening if not treated promptly
- Untreated clots can cause long-term lung damage (pulmonary hypertension)
- Clots may also damage the right side of the heart over time
Long-term outlook
With prompt diagnosis and proper treatment, most people recover fully from a pulmonary embolism. The outlook is very good, especially when treatment starts early. Long-term risks are low, and many people return to their normal activities without lasting problems.
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Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
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Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 19, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.