الفهرس 
Terminology & ClassificationOnly 14 pages are availabe for public view
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Abstract
The International Society for the Study of Vascular Anomalies (ISSVA) classification system, which has been widely embraced by various subspecialists who care for patients with these malformations, provides an approach based on histopathology, clinical course, and treatment. However, use of older nomenclature continues to cause confusion, inaccurate diagnoses, and potential mismanagement. Proper use of terminology is the first step in adequate diagnosis and planning for treatment.
Vascular anomalies can be divided into vascular tumors which shows increased cellular turnover, and vascular malformations which are the result of abnormal development of vascular elements during embryogenesis and fetal life.
According to flow characteristics and vascular channel type located in the malformation, they can be classified into High flow (Arteriovenous malformation or fistula) and low flow (venous, lymphatic, capillary or mixed) malformations. Vascular malformations can also be part of different syndromes.
Magnetic resonance imaging (MRI) is a noninvasive effective tool for imaging and classification of vascular malformations based on the presence of signal voids, and hemodynamic flow characteristics. MRI also provides details about anatomic extent of the lesion, proximity to vital structures, and involvement of multiple tissue planes. Contrast-enhanced magnetic resonance angiography (MRA) using time-resolved imaging is a relatively new and noninvasive technique that helps identify the flow characteristics, and vascular channel types in a vascular malformation.
Slow-flow venous and lymphatic malformations have high signal intensity on T2-weighted images. They can be usually
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Summary
differentiated in contrast enhanced sequences where venous malformations show diffuse homogenous delayed enhancement, while lymphatic malformations are nonenhancing lesions except for the septal component. Yet the clear cut differentiation can be difficult in many cases like mixed malformations or microcystic lymphatic ones. High-flow arteriovenous malformations and fistulas contain a signal void high flow vessels, and can be differentiated from other causes of signal void like phleboliths and calcification which show signal voids with all image sequences. They also show early arterial enhancement in dynamic time resolved MRA.
Full description of the vascular channel types, flow characteristics and extent of the vascular malformations using appropriate terminology is mandatory to avoid diagnostic confusion and for proper treatment planning and follow up.