Imaging Approach to Pulmonary Micronodules and Small Nodules

Definition:

• Micronodule = nodules of less than 3 mm
• Small nodules = nodules of less than 2 cm

Steps for Decision Making

1. Decide whether there are multiple micronodules or small nodules
2. Where are the nodules? Are they subpleural?
3. If they are subpleural, are they uniformly distributed throughout the lungs or secondary pulmonary lobules?
4. If they are not subpleural, they are likely centrilobular. The next question is whether there is tree-in-bud pattern or not.
5. Look for associated findings as a clue to limit differential diagnoses