Table 1. Ventilation/perfusion scan interpretation criteria for pulmonary embolism.

Category	Modified PIOPED II criteria
High likelihood ratio	≥2 large mismatched (ventilation-perfusion) segmental defects
Non-diagnostic	All other findings
Very low likelihood ratio	Non-segmental Q defect < chest radiograph lesion;
	1–3 segmental defects;
	Solitary matched (ventilation-perfusion: chest radiograph) defect (≤ 1 segment) in mid or upper lung;
	Stripe sign (peripheral perfusion in a defect);
	Solitary large pleural effusion (at least one third of pleural cavity);
	≥2 matched (ventilation-perfusion) defects, regionally normal chest radiograph
Normal	No Q defects

Q, perfusion. Reference: Sostman HD, Miniati M, Gottschalk A, et al. Sensitivity and specificity of perfusion scintigraphy combined with chest radiography for acute pulmonary embolism in PIOPED II. J Nucl Med 2008;49:1741-8.