Abstract
The International Society for the Study of Vascular Anomalies（ISSVA）classification system considers two main categories: vascular tumors and vascular malformations. Vascular tumors are endothelial neoplasms; they include the benign hemangiomas of infancy（infantile hemangiomas）and congenital hemangiomas as well as the borderline malignant rare kaposiform hemangioendotheliomas. Vascular malformations are developmental anomalies that are already present at birth. The flow dynamics of the lesion are then used to subclassify vascular malformations into two types: low flow（capillary, venous, lymphatic, capillary- venous, and capillary-lymphatic-venous malformations）and high flow（arteriovenous fistulas and arteriovenous malformations）. The anatomic extent of the lesion is best seen on fluid-sensitive sequences, such as fat-suppressed fast spin-echo（FSE）T2-weighted or STIR imaging. Contrast enhanced dynamic study are useful for showing whether a mass exhibits enhancement, outlining its vascularity, defining the vascular supply and venous drainage pattern, and showing arteriovenous shunting.
