MRI Pituitary — dynamic contrast-enhanced
Sella and parasellar region including both cavernous sinuses, the optic chiasm and the pituitary stalk. Whole-brain sequences are added only if a wider question is asked.
Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.
When to use it
- Biochemically proven hyperprolactinaemia, Cushing disease or acromegaly where a microadenoma is being sought.
- Hypopituitarism or diabetes insipidus of unknown cause, including stalk and posterior lobe assessment.
- A sellar or suprasellar mass identified on CT or on a routine brain MRI, needing local characterisation and chiasm relationship.
- Post-operative or post-radiotherapy follow-up of a known adenoma.
- Visual field defect with a suspected chiasmal compressive lesion.
Technique
- Thin-section small field-of-view coronal and sagittal T1 before contrast, typically 2-3 mm and thinner where hardware allows, plus coronal T2.
- Dynamic coronal T1 through the gland acquired repeatedly over roughly the first 60-90 seconds after injection, then delayed coronal and sagittal T1.
- Delayed post-contrast imaging is still needed: some adenomas are only conspicuous late, and macroadenoma extent is better shown on the delayed series.
- Reported dynamic schemes vary widely — from a handful of repetitions over 2-3 minutes to true high-temporal-resolution series — and there is no single accepted standard.
Where it goes wrong
- Slice thickness carried over from a brain protocol: a 5 mm slice will average out a 3 mm microadenoma.
- Starting the dynamic acquisition late, so both gland and lesion are already enhanced and the contrast difference is lost.
- Relying on the dynamic series alone and omitting delayed imaging.
- Failing to cover the cavernous sinuses and chiasm when the referral is actually about a macroadenoma.
- Motion between the pre-contrast and dynamic series, which makes small differences in gland signal uninterpretable.
Clinical questions that reach this study
Contrast
Macrocyclic gadolinium agent at a typical single dose of about 0.1 mmol/kg given as a bolus with saline flush, with the dynamic series started at injection.
- The dynamic series exploits a short window in which normal gland enhances before an adenoma; a slow hand injection blurs that window.
Acquisition
- Breathing
- Free breathing.
- Preparation
- IV cannula required for the dynamic series in most indications. Supply the hormone profile with the request — it determines whether a micro-lesion hunt or a macroadenoma/chiasm assessment is being asked for. A brain study alone will not answer a microadenoma question: the slice thickness is wrong.
Phases
Each phase is authored once and shared across every protocol that uses it, so the physiology below is the same wherever you meet it.
- Dynamic contrast-enhanced series (multiphase gadolinium)A late arterial acquisition timed to about 15–20 s after contrast reaches the target artery (fluoroscopically triggered or test-bolus timed), a portal venous/early venous acquisition roughly 15–30 s later, and a delayed or transitional acquisition at about 2–3 min. Confirm locally.
The same volume is imaged repeatedly across the passage of a gadolinium bolus, so enhancement is read as a curve rather than as a single value. The transferable principle is that MR sees T1 shortening rather than photon attenuation, which removes the dose penalty for repeating an acquisition and therefore makes the TEMPORAL PATTERN the primary datum: rapid arterial uptake followed by relative fall-off, progressive centripetal fill-in, and persistent late enhancement are three different diagnoses that can share an identical single-timepoint appearance. Because everything downstream depends on hitting the arterial peak within a few seconds, the phase is unusually sensitive to circulation time and to breath-hold failure, and a mistimed arterial acquisition cannot be recovered by post-processing.
Safety checks this protocol carries
Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.
- Prior contrast reaction and elective premedication· nurse pre scan
- Kidney function and gadolinium-based contrast· radiographer at scan
- Intravenous access adequate for the planned injection· radiographer at scan
- MR safety screening for implants and foreign bodies· radiographer at scan