In the left medial gastrocnemius muscle, all sequences show a heterogeneous mass.
T1-weighted images show an increase in fat around the circumference of the lesion and multiple interlacing vascular channels in the lesion, giving a “bag of worms” appearance.
STIR axial images through the hemangioma at the same level show the vascular component of the lesion to be markedly hyperintense to muscle.
On T2-weighted images, the central portion of the mass shows high signal intensity. (High-signal intralesional fat is abundant in many hemangiomas.)
Axial T1 post-contrast images show enhancement of the lesion, which is composed of a cluster of tubular structures that represent discrete vessels.