[Diagnostic imaging of osteoid osteoma].

Conventional radiography, bone scintigraphy and Computed Tomography (CT) are the most useful tools to identify osteoid osteomas. We examined 26 patients (14 men and 12 women) with osteoid osteoma in different skeletal sites (13 femora, 3 tibiae, 3 hands, 2 peroneal bones, 2 humera, 2 spines and 1 talus) and compared the diagnostic yield of the above techniques. The fundamental radiographic findings in this benign bone lesion are the presence of a "nidus", with or without calcifications, perilesional sclerosis and periosteal new bone formation. Four patients in our series had soft tissue edema. In the majority of cases, conventional radiography is the imaging method of choice, because it is easily available and its diagnostic yield is adequate (17 patients in our series), especially if combined with bone scintigraphy-whose high diagnostic sensitivity was proved in all of our patients. CT is recommended for its better spatial resolution, in view of surgery, especially when soft tissues are involved. MRI is a highly valuable tool in bone tumor staging because it demonstrates cortical involvement and intramedullary and soft tissue spread. However, MR findings might be misinterpreted as indicating a more aggressive pathologic process.