VQ Scan
Summary
Modified PIOPED Scan Criteria
 High Probability
Figure: High probability lung scan. Large perfusion defects noted without matching ventilation defects.
Figure: Intermediate probability scan with small mismatched perfusion defects not
large enough to qualify as a high probability scan.
 Two or more large (>75% of a segment) mismatched segmental perfusion defects or the arithmetic equivalent in moderate (2575% of a segment) or large and moderate defects.
 Intermediate Probability
 Two large mismatched segmental perfusion defects or the arithmetic equivalent in moderate or large and moderate defects.
 One matched V/Q defect plus a normal CXR
 Difficult to categorize as low or high or not described as low or high.
 Low probability
 Any perfusion defect with a substantially larger CXR abnormality
 >One matched VQ defects plus some normal perfusion plus normal CXR
 Any number of small perfusion defects plus normal CXR
 Nonsegmental perfusion defects (e.g., pleural effusion, cardiomegaly, enlarged mediastinal structures, raised hemidiaphragm)
 Normal
 No perfusion defects seen
Indeterminate Results



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