Figure 3c. Venous malformation of the right masseter muscle. (a) Contrast material-enhanced CT scan shows a heterogeneous mass of the right masseter muscle with faint peripheral enhancement surrounding hypoattenuating areas. The presence of a phlebolith (arrow) confirms the diagnosis of venous malformation. (b) Fast spin-echo T2-weighted MR image depicts a cavitary lesion with septation. The lesion is clearly hyperintense. (c) Gadolinium-enhanced T1-weighted MR image shows the lesion with partial heterogeneous enhancement, a finding that suggests partial thrombosis of the venous malformation.