Capillary hemangioma ( RID3972 ) General features: well defined, lobulated and heterogeneous. Twenty-five of the 27 lesions on MRI had evidence of fat, related to the periphery of the lesion and extending into the lesion, which is believed to be a reactive process resulting in fat hypertrophy. All the lesions were noted to have large internal vessels, up to 7 mm in diameter, seen easily on all imaging modalities. Avid enhancement was also identified on all CT and MR studies, which were performed after intravenous administration of contrast agent.
On MRI, 96% of lesions had significantly hyperintense signal on the T2-weighted sequences, relative to skeletal muscle, relating to dilated (cavernous) vascular spaces filled with stagnant blood. On T1-weighted sequences, 70% of lesions had only mildly hyperintense signal relative to skeletal muscle, whilst the remainder were hyperintense. This is related to fat content and serpentine vascular channels containing thrombi. The latter are a result of stagnation of blood. Large vessels were identified in 100% of lesions as linear channels of signal void on T2-weighted sequences.
Signal intensity on T1-weighted imaging of hemangiomas and malignant soft-tissue masses was similar. Subjective analysis showed greater T2 signal and gadolinium enhancement in hemangiomas; however, the differences were not statistically signiﬁcant on objective analysis. Lobulation, septation, and central low-signal intensity dots were all more common in hemangiomas, with statistical significance achieved; the combination of all three findings was specific for hemangioma.