Table 1.

Diseases and differential diagnosis of pulmonary arterial filling defect sign.

Categories	Diseases		CT	MRI	18F FDG PET	Clinical information
PTE	Acute PTE		Preserved caliber of the vessel; central or eccentric filling defect in “Polo mint” sign or “railway track” sign			Anticoagulant and thrombolytic therapy is effective
	Chronic PTE		Vessel narrowing/complete amputation; intimal irregularities; webs/bands	Mild hypointensity on fat-suppressed T2WI without enhancement on contrasted images		A history of acute PE or deep vein thrombosis
NTPE	Tumor embolism	Malignant embolism	Central or eccentric filling defect in “Polo mint” sign or “railway track” sign; tumor enhancement of the filling defect		High uptake	The history of neoplasm; no resolution and even progresses at follow-up examination despite anticoagulant or thrombolytic therapy
		Leiomyoma embolism	The fill defect originating from the uterus and extending to the inferior vena cava, right heart, and pulmonary artery			Uterine fibroids or uterine fibroid surgery history
		Angiomyolipoma embolism	The fill defect in fat intensity with contrasted enhancement		Mild uptake	Renal angiomyolipoma
	Hydatid cyst embolism		Filling defect with preserved caliber of the vessel even mild dilatation	The multi-cystic nature in hyperintensity of the filling defect on T2WI		Hydatid disease history
	Inorganic particulate embolism		High attenuation in pulmonary artery in non-contrast chest CT
Mimickers of PE	Pulmonary arterial malignancy	Pulmonary arterial sarcoma	The proximal margin of the filling defect with the “lobulated sign” or the “tongue sign”/the grape-like appearance of the distal PA with heterogeneous enhancement	Hyperintensity on fat-suppressed T2WI and DWI; hypointensity on Apparent Diffusion Coefficient (ADC) map. heterogeneous enhancement on contrasted images	Uneven high uptake	No resolution and progresses at follow-up examination despite anticoagulant or thrombolytic therapy
	Pulmonary arterial benign tumor	Pulmonary arterial myxoma		Hyperintensity on T2WI and fat-saturated sequence. More heterogeneous enhancement on late gadolinium enhancement sequences
		Pulmonary arterial lipoma	Fat intensity in pulmonary artery	High intensity in T1WI and T2WI; low intensity in fat-saturated sequence	Negative uptake	No resolution at follow-up examination despite anticoagulant or thrombolytic therapy
	Pulmonary arterial IgG4-related disease		Massive filling defects without enhancement or pulmonary artery aneurysm on CTPA		Weak uptake	Most cases had more than one organ affected, mostly with significantly increased serum IgG4 levels
	Takayasu's arteritis		Vessel narrowing/complete amputation in pulmonary artery and aorta and branches, thickened and enhanced arterial wall in “double ring sign”	Hypointensity on fat-suppressed T2WI with enhancement on gadolinium enhancement sequence in double ring sign	High uptake
	Behcet's disease/ Hughes–Stovin syndrome		Filling defect in pulmonary artery aneurysm/vessel narrowing/complete amputation/thrombosis of major veins			vasculitis and recurrent ulcers of the oral and genital mucosa, with relapsing uveitis
	PA streak artifact		filling defect in early phase contrast-enhanced imaging disappears in the late phase

CT: computed tomography; MRI: magnetic resonance imaging; PTE: pulmonary thromboembolism; T2WI: T2-weighted image; PE: pulmonary embolism; NTPE: nonthrombotic pulmonary embolism; CTPA: computed tomography pulmonary angiography.