A nidus in radiology refers to a central, distinct focus or core lesion, often a small, well-defined area that is the source or origin of a pathological process.
More specifically, in the context of osteoid osteoma, a nidus is defined as:
- A small, lucent (dark) spot, typically smaller than 1.5 cm in diameter, seen on X-rays.
- It represents the actual tumor within the bone, which causes reactive bone formation around it.
- The nidus can sometimes be identified on other imaging modalities such as CT scans and MRI.
Therefore, recognizing the nidus is crucial for diagnosis and treatment planning.
