Often caused by emboli arising from pelvic or lower extremity DVT
- Xe133 gas in closed system, get initial, equilibrium adn washout images
- Tc99m-DTPA aerosol (nebulizer)
- Defects due to consolidation, COPD (air trapping)
- Perfusion - Inject Tc99m-MAA 3-5 mCi supine, image upright
Two or more moderate/large segmental mismatch defects on VQ scan has high probability per PIOPED criteria.
Stripe Sign - rim of perfusion distal to are of decreased radiotracer uptake, low probability, likely COPD.
Fissure Sign - decreased line of perfusion a/w fluid in fissure
Triple Match - V, Q and CXR, often intermediate probability
Whole lungperfusion defect - pulmonary agenesis, hilar mass, medistinal fibrosis