Suspected pituitary or sellar lesion

Pituitary Society prolactinoma consensus (2023); Endocrine Society pituitary incidentaloma guideline

A whole-brain MRI is the wrong study for a gland that is roughly a centimetre across. The dedicated dynamic protocol exists because a microadenoma is defined by a difference in enhancement timing, not by a difference in signal.

Biochemical evidence of pituitary hyper- or hypofunction, a visual field defect suggesting chiasmal compression, or a sellar abnormality noticed on imaging performed for another reason.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Accept as requested

MRI Pituitary — dynamic contrast-enhanced

MRI Pituitary

What we'd amend, and why

Sensitivity for a microadenoma is a function of voxel size and enhancement timing, and a whole-brain acquisition fails on both. Thin coronal and sagittal sections through the sella, acquired dynamically during contrast arrival, exploit the fact that adenoma tissue enhances later than the normal gland — a difference that is present for less than a minute and absent on any routine post-contrast series. The same acquisition defines the relationship to the optic chiasm and to the cavernous sinuses, which is what a surgeon needs.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwayadult — Adults
rulerule-mr-device-screening — MR safety screening for implants and foreign bodies; checked by Radiographer at the scanner
rulerule-contrast-reaction-premed — Prior contrast reaction and elective premedication; checked by Nurse before the scan
rulerule-gadolinium-renal — Kidney function and gadolinium-based contrast; checked by Radiographer at the scanner
rulerule-pregnancy-gadolinium — Gadolinium in known or possible pregnancy; checked by Radiographer at the scanner
rulerule-iv-access — Intravenous access adequate for the planned injection; checked by Radiographer at the scanner

Decision support only. Local protocol takes precedence.

Handled at the scanner(2)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

MR safety screening for implants and foreign bodies
Complete the MR safety questionnaire, verify implant labelling and its stated conditions of use against this scanner and this protocol, and ensure no ferromagnetic object enters Zone IV.
Radiographer at the scannerBefore the scan
Flags back if: An implant or retained foreign body that is MR Unsafe, unlabelled, or cannot be identified; or an MR Conditional device whose stated conditions this scanner or the requested protocol cannot satisfy; or a credible unexcluded intraocular metallic foreign body history.
Intravenous access adequate for the planned injection
Site and test a cannula that supports the protocol flow rate, preferring an antecubital or large forearm vein, and observe the injection for extravasation. A 20-gauge or larger cannula is preferred for flow rates of 3 mL/s or more.
Radiographer at the scannerAt the scanner
Flags back if: No cannula can be sited that supports the protocol flow rate — for example only a 22-gauge hand or foot cannula for a CT angiogram needing 4–5 mL/s; or the only available access is a central line or port that is not labelled power-injectable; or an extravasation occurs.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

Adults

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	MRI Pituitary MRI Pituitary — dynamic contrast-enhanced usually appropriate	Sensitivity for a microadenoma is a function of voxel size and enhancement timing, and a whole-brain acquisition fails on both. Thin coronal and sagittal sections through the sella, acquired dynamically during contrast arrival, exploit the fact that adenoma tissue enhances later than the normal gland — a difference that is present for less than a minute and absent on any routine post-contrast series. The same acquisition defines the relationship to the optic chiasm and to the cavernous sinuses, which is what a surgeon needs.
Second line	CT Head CT Head — Unenhanced and Post-Contrast	Only where MRI is genuinely impossible. CT will show a macroadenoma, bony sellar expansion and the sphenoid anatomy relevant to a transsphenoidal approach, and it will reliably miss a microadenoma. A negative CT therefore has almost no value against this question and should be reported that way.

Pitfalls

Booking a routine brain MRI for this question. It is the single commonest reason a microadenoma is missed, and the study then has to be repeated.
Imaging only after contrast has equilibrated, which is when an adenoma becomes isointense to the gland and vanishes.
Over-calling physiological gland asymmetry and convexity, particularly in young women and in pregnancy where the gland normally enlarges.
Missing pituitary apoplexy in an acute severe headache with visual loss, which needs an urgent study rather than an outpatient slot.
Failing to comment on chiasmal contact and cavernous sinus invasion, which are the findings that determine surgical approach.

Priors — what to pull first

Compare with any previous pituitary study using the same plane and slice thickness; apparent growth across differently acquired studies is frequently artefactual.
After surgery or radiotherapy, the operative note and the immediate post-operative baseline are needed before residual tumour can be called.

What makes a good request

State the hormonal abnormality. A search for a 3 mm corticotroph microadenoma and the assessment of a known macroadenoma against the chiasm need the same study set up differently.
Dynamic acquisition matters because a microadenoma enhances more slowly than the normal gland; on delayed images the two equalise and the lesion disappears.
Where the finding is an incidental sellar lesion, the questions become size, chiasmal contact and cavernous sinus involvement, and formal visual fields and pituitary function testing belong alongside the scan.
Pituitary apoplexy is on this card only to be taken off it. Sudden severe headache with visual loss, ophthalmoplegia, reduced consciousness or hypotension is an emergency, not an outpatient dynamic study: hydrocortisone is given on suspicion before any imaging, the study is an urgent MRI of the sella in which the unenhanced sequences alone show the haemorrhage, and where MRI cannot be delivered quickly an unenhanced CT is done instead because it will show acute blood in an enlarged gland. Requesting a dynamic microadenoma protocol for that patient is the wrong study at the wrong speed.

Scoring this once it is done

The classification and risk tools this question ends in.

Knosp Classification (Pituitary Adenoma)

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

MRI Pituitary — dynamic contrast-enhanced CT Head — Unenhanced and Post-Contrast

Confirm locally

MRI Pituitary — dynamic contrast-enhanced: timings are typical — confirm against local protocol.
Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.