Suspected primary brain tumour

ACR AC Brain Tumors (2025 rev)

Contrast-enhanced MRI with a standardised tumour protocol, because the request is simultaneously a diagnostic question and the first step of a surgical plan, and a non-standard baseline compromises every follow-up study that comes after it.

Progressive focal deficit, personality change, new seizures with a focal onset, or a mass already seen on a CT 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

Time since onset

Decides thrombolysis and thrombectomy windows, testicular salvage, and whether an ischaemic limb is still salvageable.

GCS

Focal neurological deficit

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 Brain — tumour protocol

MRI Brain

What we'd amend, and why

Three things decide management here and only MRI provides them: the extent of non-enhancing infiltration on FLAIR, which usually exceeds the enhancing component and defines the resection target; the relationship of the lesion to eloquent cortex and white matter tracts; and the enhancement pattern with diffusion characteristics that separate high-grade tumour from abscess, lymphoma and demyelination. A standardised acquisition also becomes the measurable baseline against which every subsequent response assessment is made.

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-paeds-sedation — Sedation or anaesthesia for a child; checked by Nurse before the scan
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.

Deficit of hours, or a depressed conscious level — CT first

Role	Study & protocol	Why this answers the question
First line	CT Head CT Head — Unenhanced usually appropriate	A tumour presents over weeks; a deficit measured in hours is a vascular event until proved otherwise, and a falling conscious level is mass effect, hydrocephalus or haemorrhage into a lesion. All three are questions an unenhanced CT answers in seconds and a twenty-minute tumour protocol answers too late — and the immediate decisions that follow, steroids, a neurosurgical call, transfer, are made on the CT. It does not replace the MRI: it establishes that there is time to do it properly.
Second line	MRI Brain MRI Brain — tumour protocol	Unchanged in content and deferred by a few hours: the standardised tumour protocol is still what maps non-enhancing infiltration on FLAIR, relates the lesion to eloquent cortex and gives the measurable baseline every later response assessment is compared against. Acquiring it once the patient is stable is what protects that baseline from a motion-degraded emergency acquisition.

Adults

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	MRI Brain MRI Brain — tumour protocol usually appropriate	Three things decide management here and only MRI provides them: the extent of non-enhancing infiltration on FLAIR, which usually exceeds the enhancing component and defines the resection target; the relationship of the lesion to eloquent cortex and white matter tracts; and the enhancement pattern with diffusion characteristics that separate high-grade tumour from abscess, lymphoma and demyelination. A standardised acquisition also becomes the measurable baseline against which every subsequent response assessment is made.
Second line	CT Head CT Head — Unenhanced	The usual entry point rather than the answer. An unenhanced CT detects mass effect, hydrocephalus, calcification and haemorrhage within a lesion, and it is what triages a deteriorating patient to neurosurgery tonight. It cannot grade, cannot map infiltration and cannot plan a resection.

Pitfalls

Accepting an unenhanced MRI for a suspected tumour, which cannot characterise the lesion or plan surgery.
Assuming enhancement equals high grade. A substantial proportion of low-grade gliomas enhance and some high-grade tumours do not.
Missing lymphoma by imaging after corticosteroids have been started, which can make the lesion shrink and stop enhancing.
Reporting a solitary lesion without diffusion, which is what separates an abscess from a necrotic tumour.
Failing to flag suspected leptomeningeal spread, which requires whole-neuraxis coverage rather than a brain study alone.

Priors — what to pull first

A stable appearance across years of prior imaging effectively excludes a high-grade tumour and reframes the lesion entirely.
Where surgery has already occurred, the immediate post-operative study within the first 72 hours is the reference for residual disease; later enhancement is confounded by surgical granulation tissue.

What makes a good request

If a lesion has already been seen on CT, say so and say where. The question becomes characterisation and surgical planning, which changes which sequences are essential.
A standardised protocol matters beyond the first study: response assessment compares like with like, and a baseline acquired with ad hoc parameters cannot be measured against later scans.
Perfusion and spectroscopy are problem-solving additions for grading and for separating tumour from treatment effect, not routine components of a first diagnostic study.

Scoring this once it is done

The classification and risk tools this question ends in.

RANO Criteria (High-Grade Glioma)Knosp Classification (Pituitary Adenoma)

How these studies are acquired

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

CT Head — Unenhanced MRI Brain — tumour protocol

Confirm locally

MRI Brain — tumour protocol: 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.