Pulmonary SPECT imaging and the stripe sign.

A patient with high clinical suspicion for pulmonary embolism underwent a diagnostic scintigraphic ventilation/perfusion scan. The planar images revealed an unmatched perfusion defect with a stripe sign in the right middle lobe. A stripe sign is the appearance of normally perfused tissue between the defect and the pleural surface suggesting a nonpleural-based abnormality. SPECT images acquired in the same study period, however, failed to demonstrate normally perfused tissue between the defect and the pleural surface. Previous studies have compared planar ventilation/perfusion studies with stripe sign perfusion defects to pulmonary angiography. The results suggest that stripe sign perfusion defects are generally not due to emboli. However, planar imaging is projectional and may miss pleural contact in some perfusion lesions depending on the projection. In the absence of SPECT data, the significance of the stripe sign may need to be reassessed.