PITUITARY ADENOMA - MICRO VS MACRO DIFFERENTIATION
Pituitary adenomas constitute 10% of all intracranial neoplasms. They are classified anatomically based on size:
- micro-adenoma if less than 10mm and
- macro-adenoma if more than 10mm in diameter.
- secretory or
When a patient is suspected to have hyperprolactinemia not associated with drugs, MR imaging is the foremost and only imaging technique that can depict a pituitary adenoma.
- Most micro-adenomas have lower signal intensity than the normal pituitary gland on T1-weighted images. A convex outline of the pituitary gland or deviation of the pituitary stalk can also be detected.
- Dynamic study with intravenous bolus injection of contrast medium is the preferred technique for assessing micro-adenomas, as it allows excellent delineation between the tumour and the normal pituitary gland. In the dynamic study, the normal pituitary gland and stalk show strong enhancement in the early phase of dynamic imaging, whereas micro-adenomas show relatively weak enhancement.