FLEX February 2024

Stern et al

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Fig. 7. Epidermoid. Axial T2 MRI ( A ) shows a hyperintense focus in the left temporal calvarium ( arrow ). Diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) images show corresponding restricted diffusion within the lesion ( arrows ).

hemorrhage fluid levels related to prior hemorrhage or infection ( Figs. 13 and 14 ), as well as phleboliths, which manifest as low signal foci on MRI 23 and hyperdense calcific foci on CT. Venolymphatic malformations may be heterogeneous in appearance, and may be difficult to distinguish from some neoplastic lesions. These lesions are charac terized by a low-flow pattern of vascularity on time-resolved magnetic resonance angiography. 24 Infantile hemangioma Proliferating infantile hemangiomas typically appear as well-circumscribed masses with high signal on T2 weighted images, and demonstrate prominent enhancement and vascularity with conspicuous flow voids ( Fig. 15 ). However, involuting hemangi omas can display focal areas of high signal on T1 weighted images due to fatty replace ment. 23 Large (>5 cm) facial hemangiomas, particularly in the V3 distribution, may be associated with other abnormalities of the posterior fossa, as well as abnormalities of

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