Magnetic resonance imaging • T1: Nidus is isointense to muscle. • T2: Nidus shows intermediate to high signal. Peak contrast enhancement occurs during the arterial phase with early partial washout. Extensive bone marrow edema may be present, which can obscure the nidus. • Bone scan: Uptake of radioactive tracer is increased. May appear as a small focus of intense activity surrounded by a larger area of increased activity. • Angiography: Vascularity is increased in the region of the lesion with dense enhancement of the nidus. A feeding vessel may be identified. osteoid osteoma cc radsource, paeds thieme