Table 3.

Semiology of lung ventilation/perfusion pathology with V/P_SPECT. Interpretation and differential diagnosis

Semiology			Diagnosis	Probability that the semiologic pattern is diagnostic	Level of evidence
Pattern	Distribution	Area
Mismatch	Segmental	1 segment	PE*	Very high
		≥ 2 subsegments	PE*	Very high
		≤ 1 subsegment	Non-PE	High
	Total lung unperfused	Total lung	Tumour#	High
			Abscess#	High
			Massive PE	Very low (rare)	Very rare condition
	Nonsegmental	Systematically antigravitational redistribution	Heart failure	High
		Irregular	Vasculitis	Very low (rare)	Very rare condition, expert opinion
Match	Segments or lobules	No stripe sign	Tumour	Depends on clinical context
			Atelectasia
			Empyema
		Stripe sign	Pneumonia evolutioned stage	High
Reverse mismatch§	Segments or lobules	Stripe sign	Pneumonia initial stage	High
		No stripe sign	COPD	High

*Even in the presence of concomitant pathologies

^#Recommend CTPA

^§More reduction of ventilation than perfusion