Purpose or Case Report: On conventional MRI pediatric vasoproliferative neoplasms or vascular malformations may demonstrate similar features including T2 hyperintensity and enhancement. Hemangiomas can appear similar to vascular malformations when there are large feeding vessels.
Our objective is to illustrate typical imaging findings of vasolproliferative neoplasms and vascular malformations of the head and neck on conventional MRI and the benefits of time resolved MRA to further distinguish between high and slow flow lesions
Methods & Materials: We performed a retrospective review to identify patients with vascular lesions of the head and neck seen at our tertiary care facility. We selected a total of five patients to illustrate the typical imaging findings of a hemangioma, arteriovenous malformation (AVM), arteriovenous fistula (AVF), venous malformation, and lymphatic malformation.
For each entity we present conventional MRI images, conventional MRA/MRV, and multiple time points of time resolved MRA. Time resolved MRA was performed by sampling lower spatial frequencies more often than higher spatial frequencies. After an initial pre-contrast mask, images are obtained over multiple time points during flow of contrast through arterial, capillary, and venous phases for a minimum of 15 phases.
Results: Time-resolved MRA is a useful tool to help distinguish types of vascular lesions. Spatial resolution is sacrificed in lieu of improved temporal resolution. On time resolved MRA, hemangiomas demonstrate avid, homogeneous, early arterial enhancement (Case 1). The arterial phase may show prominent feeding vessels, but there should not be draining veins. AVMs and AVFs, on the other hand, demonstrate enhancement of both the feeding arteries and draining veins during the early arterial phase (Case 2, Case 3). Tortuous neovascularity during the arterial phase is suggestive of an alternative diagnosis of another solid tumor. Venous malformations demonstrate no enhancement in the early arterial phase and usually show patchy areas of enhancement, possible puddling of contrast, and enlarged draining and surrounding veins in the venous phase (Case 4). Lymphatic malformations show no or very limited enhancement during time-resolved MRA (Case 5).
Conclusions: Using case examples, we illustrate the typical imaging appearance on time resolved MRA of commonly encountered vascular lesions of the head and neck.