Case of the Day - 038 - 2025 05 20 - Vascular Groove, Dark Rim, and Arterial Enhancement Signs of Osteoid Osteoma 21-years old patient with CT and MRI findings of a long standing intra-capsular osteoid osteoma of the proximal right tibia. Even though there is no cortical thickening and the lesion is medullary, which may happen with intra-capsular lesions, the other signs... - vascular groove - dark rim - arterial enhancement on dynamic contrast ...are typical for the diagnosis of osteoid osteoma. YouTube video link https://youtu.be/1bveIW2nnlY #caseoftheday #osteoidosteoma #bonetumor