MR of osteoid osteoma. Sagittal T2-w fat saturated MRI image of a 1-cm cortical osteoid osteoma (white arrowhead) with prominent bone marrow edema surrounding the left femoral neck lesion. The location of the intraarticular lesion allows for an unobstructed treatment window (i.e., no nerves or other vital structures are present in the ultrasound path)