MRI Brain — routine unenhanced
Vertex to foramen magnum, including the whole cerebellum and craniocervical junction.
Typical, not policy
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
- Persistent or red-flag headache where structural disease needs excluding.
- First unprovoked seizure in an adult, as the initial structural survey before any epilepsy-specific protocol.
- New focal neurological deficit outside the hyperacute stroke pathway.
- Cognitive decline and suspected neurodegenerative disease, where volume loss patterns and vascular burden are the question.
- Follow-up of a known unenhancing abnormality where the previous study was also unenhanced.
Technique
- Typical core: axial or 3D T1, axial T2 TSE, axial or 3D FLAIR, axial DWI with b0 and b1000 plus ADC map, and a susceptibility-weighted or T2* gradient-echo sequence for blood products.
- Sagittal T1 or a sagittal reformat from a 3D acquisition for midline structures and the pituitary region.
- Coronal T2 or FLAIR added where the temporal lobes or hippocampi are relevant.
- Field strength changes the trade-offs: 3 T buys resolution and DWI signal but increases susceptibility artefact at the skull base.
Where it goes wrong
- Requesting contrast by reflex. Gadolinium adds cost, time and a small risk, and answers nothing in most headache, seizure-screen and dementia referrals.
- Omitting a susceptibility-sensitive sequence, which is the sequence that detects microhaemorrhage, cavernoma and superficial siderosis.
- Slice thickness inherited from a general protocol will under-sample the temporal lobes and the brainstem; targeted questions need targeted planning.
- DWI is degraded by susceptibility at the skull base and near the frontal sinuses, which is exactly where small lesions get missed.
Clinical questions that reach this study
Known or suspected lung cancer — stagingSuspected acute ischaemic strokeSuspected intracranial haemorrhage (non-traumatic)Suspected subarachnoid haemorrhageFirst unprovoked seizureDrug-resistant epilepsy — pre-surgical assessmentSuspected brain metastasesSuspected primary brain tumourSuspected multiple sclerosis or first demyelinating eventSuspected meningitis or encephalitisHeadache with red flag featuresHeadache without red flags (migraine, tension-type, chronic stable)Suspected normal pressure hydrocephalusCognitive impairment or suspected dementiaHead injury in childrenSuspected inflammatory spinal cord lesion (transverse myelitis)Chronic rhinosinusitis and pre-operative sinus CTSuspected physical abuse in a child — skeletal survey
Contrast
None
- No intravenous contrast. Most non-oncological brain questions are fully answered unenhanced.
- If the finding on the unenhanced study needs characterising, contrast can be added at the same visit rather than pre-emptively.
Acquisition
- Breathing
- Free breathing. Head immobilisation and clear instruction to keep still are the quality determinants.
- Reconstruction
- Multiplanar reformats from the 3D acquisitions where a volumetric sequence is used.
- Preparation
- No fasting or bowel preparation for an unenhanced brain study. Establish whether gadolinium is actually needed before booking an IV slot — most brain questions do not require it. Young children and patients unable to keep still for 20-30 minutes need a sedation or general anaesthetic pathway agreed in advance.
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.
- MR safety screening for implants and foreign bodies· radiographer at scan
- Sedation or anaesthesia for a child· nurse pre scan