Vascular anomalies include:
- venous malformations,
- arteriovenous malformations,
- arteriovenous fistulas,
- mixed lesions.
The term hemangioma has also been used generically to describe all of these vascular anomalie. Vascular anomalies are more common in females. They are usually congenital except for post-traumatic arteriovenous fistulas.
Imaging and Location
On MR images, hemangiomas have similar signal intensity as muscle with T1 weighting and high signal intensity with T2 weighting. The signal is usually heterogeneous with T2 weighting and may be either homogeneous or inhomogeneous with T1 weighting and may contain variable amounts of fat and vessels within the mass.
Phleboliths are seen as focal areas of low signal intensity on all imaging sequences, but they are better identified on plain radiographs or CT scans. Serpiginous areas of low signal intensity are occasionally seen and represent flow void in larger feeding arteries or draining veins.
On MR images, arteriovenous malformations and arteriovenous fistulas have large tortuous vessels with flow void due to rapidly flowing blood. Feeding and draining vessels can be identified as vascular structures, but differentiation of veins and arteries is not always possible