List six causes of single or multiple focal areas of decreased osseous uptake (cold lesions).

1. Radiation therapy
2. Early osteonecrosis
3. Infarction (very early or late)
4. Anaplastic tumor (e.g., renal cell carcinoma, thyroid carcinoma, neuroblastoma, multiple myeloma)
5. Artifact from overlying attenuating material (e.g., a metal prosthesis or other dense object)
6. Hemangioma