title: "Doughnut" sign in avascular necrosis of the bone.
mesh_terms: D002675:Child, Preschool; D005624:Frontal Bone / Q000000981:diagnostic imaging*; D006801:Humans; D010020:Osteonecrosis / Q000000981:diagnostic imaging*; D011859:Radiography; D011877:Radionuclide Imaging