Table 1.

Characteristic imaging features of vascular malformations

Malformation type	All imaging modalities (diagnostic value in flow-characteristics)	MRI features	Ultrasound
Slow-flow VM	Ultrasound (3) CDUS/CEUS (1/3) X-ray (1) MRI and MRV (3) Transvenous phlebography (3)	Septated lobulated mass without mass effect Phleboliths (low SI), fluid-fluid levels, low SI on T1WI, high SI on T2WI No flow voids on SE images Infiltrates tissue planes and possible surrounding oedema No arterial or early venous enhancement Slow gradual enhancement and diffuse enhancement on delayed images with some late enhancement (≥ 5 s) Normal afferent arteries Contrast pooling in dilated stagnant venous spaces in later venous phase imaging	Variable appearance (spongiform, multicystic, uncommon as dilated tubular channels) Usually heterogeneous, mostly hypoechoic intralesional phleboliths (calcifications) may be present Localized or involving multiple soft-tissue planes Spontaneous echo contrast, absence of spontaneous flow, luminal filling, and venous flow pattern detectable with provocative maneuvers (proximal or distal compression)
Slow-flow LM	Ultrasound (3) MRI (2)	Septated lobulated mass with some fluid–fluid levels Infiltration of tissue planes Low SI on T1WI, high SI on T2WI No flow voids on SE images Rim and septal enhancement No significant or slight diffuse enhancement	Macrocystic: Multicystic with thin septa Variable echogenicity of cystic contents, sometimes with fluid-fluid levels, especially if complicated with hemorrhage No flow or low vascular density on color Doppler, confined to septa Microcystic: Ill-defined and hyperechoic, containing scattered cysts < 1–2 cm Sometimes no visible cysts No flow or low vascular density on color Doppler
High-flow AVM	Ultrasound (1) CDUS/CEUS (3/3) MRI and MRA (2) Perfusion CT with CTA (3) Catheter angiography (3)	No well-defined mass Infiltration of tissue planes Flow voids on SE images Enlarged feeding arteries and draining veins Hypertrophied tortuous afferent arteries and efferent veins Direct arteriovenous communications via vascular nidus Early enhancement of arteriovenous lesion (≤ 5 s) Early enhancement of enlarged feeding arteries and nidus with shunting to draining veins	Conglomerate of tortuous, dilated vessels without discrete mass that can involve multiple soft-tissue planes Pulsatile flow with high velocities, low resistance, and spectral broadening

Diagnostic value: 1, moderate; 2, good; 3, high