Fig. 1

Example images of osteoid osteoma. A The X-ray image shows the sclerotic bone thickening around the osteoid osteoma. B In the CT, the osteoid osteoma is seen as the central lucency with circumferential reactive bone sclerosis. C In the T1-weighted MRI image post-contrast, the tumor nidus is seen as hyperintensity within the thickened surrounding low intensity cortical bone (arrow). Hyperintense edema surrounds the reactive periostium (arrowhead). D The T2-weighted MRI image shows the mildly hyperintense tumor nidus (arrow) with periostial edema (arrowhead)