V/Q Scan (Ventilation/Perfusion Scan)
Nuclear medicine test that evaluates lung airflow (ventilation) and blood circulation (perfusion) to diagnose pulmonary embolism.
What is V/Q?
A V/Q scan is a nuclear medicine procedure that evaluates both the air supply (ventilation) and blood flow (perfusion) to the lungs. It involves two separate imaging studies - one using inhaled radioactive gas to show air movement, and another using injected radioactive tracer to show blood flow patterns. This dual assessment helps detect abnormalities like pulmonary embolism that would cause a mismatch between ventilation and perfusion.
How it works: The ventilation portion uses inhaled xenon-133 or technegas gas that distributes through the airways. The perfusion portion uses injected Tc-99m MAA (macroaggregated albumin) particles that travel to the lungs and lodge in small blood vessels. Special gamma cameras capture images of both studies, which are then compared to identify areas where lung tissue is ventilated but not perfused (suggestive of PE) or other ventilation-perfusion mismatches.
Common Uses of V/Q
PE in Pregnancy
Preferred imaging modality for suspected PE in pregnant patients due to lack of ionizing radiation to the fetus compared to CT.
Allergy to IV Contrast
Alternative to CT pulmonary angiography for patients with known severe contrast allergies or previous reactions to iodinated contrast.
Renal Insufficiency
Excellent alternative for patients with advanced CKD or ESRD who cannot receive iodinated contrast due to risk of contrast-induced nephropathy.
Advantages
- ✓No ionizing radiation to the fetus in pregnant patients
- ✓No iodinated contrast exposure
- ✓Can detect other pulmonary abnormalities
- ✓Lower radiation than CT pulmonary angiography
- ✓Good at identifying chronic vascular changes
Limitations
- ⚠Less specific than CT pulmonary angiography
- ⚠Interpretation can be challenging with pre-existing lung disease
- ⚠Limited availability compared to CT
- ⚠Requires patient cooperation with breathing
- ⚠Cannot detect small subsegmental PEs as well as CT
Preparation Checklist
0 of 14 completed
⚖️V/Q vs CT
Related Imaging Modalities
Often used in conjunction with chest X-ray. CT pulmonary angiography is usually preferred when available and appropriate.
CT
CT scans use X-rays to create detailed cross-sectional images of the body. They are particularly useful for detecting bone fractures, tumors, and internal bleeding.
MRI
MRI uses powerful magnets and radio waves to produce detailed images of organs and soft tissues. Excellent for brain, spine, and joint imaging.
Ultrasound
Ultrasound uses sound waves to create real-time images. Commonly used for pregnancy monitoring and examining organs like the heart, liver, and kidneys.
Browse V/Q Terms
Explore common terms in V/Q reports, each with detailed explanations, clinical significance, and related lab tests to help you understand your imaging results. lab tests.
Chronic Thromboembolic Disease VQ Scan: What It Shows, Cost
Persistent perfusion defects that don't resolve after anticoagulation. May show mosaic perfusion pattern, wedge-shaped defects at clot sites, and evidence of pulmonary hypertension with enlarged central arteries.
Pulmonary Embolism VQ Scan: What It Shows, Cost & Preparatio
Ventilation-perfusion mismatch: areas with normal ventilation but absent or decreased perfusion indicate pulmonary embolism. Multiple segmental or larger perfusion defects with normal ventilation are diagnostic.
Pulmonary Hypertension VQ Scan: What It Shows, Cost & Prepar
Patchy, non-segmental perfusion defects that don't match ventilation patterns. Chronic PE may show 'mosaic perfusion' with areas of both increased and decreased uptake. May see normal perfusion with enlarged central arteries.
Pulmonary Embolism VQ Scan: What It Shows, Cost & Preparatio
Segmental or lobar perfusion defects with preserved ventilation (V/Q mismatch). Multiple wedge-shaped peripheral defects are characteristic. High-probability scan shows two or more large segmental mismatched defects.
Lung Ventilation Perfusion Scan for COPD: What It Shows, Cos
Heterogeneous ventilation with areas of delayed wash-in and wash-out, particularly in upper lobes. Perfusion shows redistribution patterns with reduced upper lobe flow. Matched V/Q defects in emphysematous regions. May show 'hot spots' on ventilation in severe disease.
Pre-operative Lung Resection Quantitative VQ: What It Shows,
Quantitative regional perfusion distribution showing percentage of total lung function contributed by each lobe and lung. Pre-operative scan establishes baseline; post-operative predictions calculated based on planned resection extent. May show heterogeneous distribution in diseased lungs.
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