Pituitary MRI (Sella / Dynamic Contrast)

Dedicated pituitary MRI is the gold standard for imaging the sella and parasellar region. A small field-of-view, thin-section protocol with dynamic post-contrast imaging exploits the differential enhancement kinetics of normal gland and adenoma to detect small lesions that determine endocrine management and surgical planning.

Indications

Biochemically suspected functioning adenoma (prolactinoma, GH-secreting, ACTH-secreting)
Non-functioning macroadenoma with mass effect, visual failure or hypopituitarism
Investigation of hyperprolactinaemia, acromegaly and Cushing disease
Central diabetes insipidus and assessment of the posterior pituitary bright spot and stalk
Suspected pituitary apoplexy, Rathke cleft cyst, craniopharyngioma or hypophysitis
Post-operative and post-radiotherapy surveillance of pituitary tumours

Contraindications & Cautions

Non-conditional pacemakers, ICDs, neurostimulators and ferromagnetic aneurysm clips
Cochlear implants and unstable metallic intra-ocular foreign bodies
Severe claustrophobia without sedation
Gadolinium caution with eGFR <30 mL/min/1.73 m2 (NSF risk)
Pregnancy: perform unenhanced imaging where possible; avoid gadolinium unless essential

Patient Preparation

MRI safety screening and removal of ferromagnetic objects
Intravenous cannula for dynamic gadolinium administration
Explain the need to remain still during the rapid dynamic acquisition
Correlate with endocrine results (prolactin, IGF-1, cortisol axis) to focus interpretation
For suspected microadenoma, ensure the dynamic sequence timing is set up before contrast injection

Technique & Parameters

Small field-of-view (16-20 cm) dedicated sella coil positioning
Thin-section (2-3 mm, no or minimal gap) coronal and sagittal T1 pre-contrast and coronal T2
Dynamic thin-section coronal spoiled gradient-echo or fast spin-echo T1 acquired repeatedly during gadolinium bolus (temporal resolution ~20-30 s)
Delayed post-contrast coronal and sagittal T1 for macroadenoma extent and cavernous sinus assessment
Optional 3T high-resolution and volumetric sequences for very small lesions
Include the optic chiasm, cavernous sinuses and suprasellar cistern in coverage

Systematic Review

Assess gland height, superior margin convexity and symmetry (upper limit ~9-10 mm, higher in pregnancy/puberty)
Confirm the posterior pituitary bright spot and midline infundibulum position
On dynamic images, look for a focus enhancing later/less than the avidly enhancing normal gland (microadenoma)
Evaluate suprasellar extension, optic chiasm compression and third ventricle
Assess cavernous sinus invasion using the Knosp grading relative to the internal carotid arteries
Review sphenoid sinus, clivus and parasellar structures

Key Findings & Significance

Microadenoma (<10 mm): focal region of delayed/reduced enhancement on dynamic imaging, often T1 hypointense
Macroadenoma (>10 mm): sellar mass with suprasellar extension and a figure-of-eight or snowman configuration at the diaphragma
Optic chiasm compression producing bitemporal hemianopia
Cavernous sinus invasion with encasement of the cavernous internal carotid artery (higher Knosp grade)
Pituitary apoplexy: haemorrhage/infarction with fluid level and heterogeneous signal in an enlarged gland
Loss of the posterior pituitary bright spot and thickened stalk in central diabetes insipidus/hypophysitis

Differential Considerations

Sellar mass: pituitary adenoma, Rathke cleft cyst, craniopharyngioma, meningioma, hypophysitis
Suprasellar mass: craniopharyngioma, meningioma, hypothalamic glioma, germinoma, aneurysm
Cystic sellar lesion: Rathke cleft cyst, cystic adenoma, arachnoid cyst, craniopharyngioma
Thickened stalk: lymphocytic hypophysitis, sarcoidosis, Langerhans cell histiocytosis, germinoma, metastasis
Physiological gland enlargement in puberty, pregnancy and lactation mimicking pathology

Pearls & Pitfalls

Timing is critical: on dynamic imaging the normal gland enhances first, so a microadenoma is seen as a transient relative filling defect
A convex upper gland border and stalk deviation are supportive but non-specific signs of a microadenoma
Prolactin levels correlate with tumour size; a large macroadenoma with only modest prolactin elevation suggests a non-functioning tumour with stalk effect
The Knosp grade predicts the likelihood of surgical cavernous sinus residual disease
Always exclude an aneurysm before diagnosing a parasellar mass; flow void and MRA help

Structured Report

State protocol, field strength and whether dynamic contrast was performed
Report gland dimensions, lesion size, location and enhancement characteristics
Describe suprasellar and parasellar extension, chiasm compression and Knosp cavernous sinus grade
Comment on the posterior bright spot and infundibulum where relevant
Provide an impression correlated with endocrine data and surgical/medical recommendation

References

Bonneville F, et al. Radiographics: Imaging of the pituitary gland and sellar region
Knosp E, et al. Pituitary adenomas with invasion of the cavernous sinus space
ACR-ASNR-SNIS-SPR Practice Parameter for the Performance of MRI of the Brain
FitzPatrick M, et al. Dynamic contrast-enhanced pituitary MRI. AJNR

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

Pituitary MRI (Sella / Dynamic Contrast)

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References