Brain MRI with Contrast

Contrast-enhanced brain MRI is the primary imaging modality for evaluating intracranial pathology owing to its superior soft-tissue contrast and multiparametric characterization. It combines anatomical, fluid-sensitive, diffusion, and post-gadolinium sequences to detect and characterize tumors, demyelination, ischemia, infection, and other processes. Gadolinium enhancement identifies blood-brain barrier breakdown and abnormal vascularity. It is central to diagnosis, treatment planning, and follow-up across neuro-oncology, neuroinflammatory, and neurodegenerative disease.

Indications

Suspected or known intracranial neoplasm (primary or metastatic) for detection, characterization, and treatment response
Evaluation and monitoring of multiple sclerosis and other demyelinating/inflammatory disease per revised McDonald criteria
Suspected CNS infection: abscess, meningitis, encephalitis, ventriculitis
New-onset seizures, focal neurological deficit, or suspected cortical malformation
Pituitary and sellar/parasellar lesions with dedicated thin-section dynamic pituitary protocol
Cognitive decline/dementia workup and characterization of neurodegenerative patterns
Cranial nerve palsy, sensorineural hearing loss (IAC protocol), and skull base pathology
Characterization of acute or subacute stroke and its complications when CT is indeterminate

Contraindications & Cautions

Non-MRI-conditional cardiac pacemakers/defibrillators, cochlear implants, certain neurostimulators, and ferromagnetic intracranial aneurysm clips
Intraocular or intracranial ferromagnetic foreign bodies (orbital radiograph if metalworker history)
Severe renal impairment (eGFR <30) is a relative contraindication to gadolinium due to nephrogenic systemic fibrosis risk; use macrocyclic agents and weigh risk-benefit
Known severe gadolinium hypersensitivity; prior anaphylactoid reaction
Pregnancy: avoid gadolinium unless the benefit clearly outweighs risk, as it crosses the placenta
Severe claustrophobia or inability to remain still may require sedation or anesthesia

Patient Preparation

Screen thoroughly for implants, devices, prior surgery, and metallic foreign bodies with a completed MRI safety questionnaire
Check renal function (eGFR) prior to gadolinium administration per local protocol
Obtain informed consent for contrast; document prior contrast reactions and allergies
No fasting required for a standard study; ensure hydration
Establish reliable IV access (typically 20-22G) for power or hand injection of gadolinium
Remove all metallic objects, dentures, hearing aids, and provide hearing protection
Position supine, head-first, immobilize head within the dedicated head coil; explain scan duration and provide alarm bulb

Technique & Parameters

Field strength 1.5T or 3T using a multichannel head/neurovascular coil
Sagittal T1 localizer, axial T2 FSE, axial and 3D FLAIR for edema and demyelination
Axial DWI with ADC map (b=0 and b=1000) for acute ischemia and cellularity
Axial or volumetric T1 pre-contrast, then T1 post-gadolinium in axial, coronal, and sagittal planes
Susceptibility-weighted imaging (SWI/GRE) for hemorrhage, microbleeds, and calcification
Slice thickness 3-5 mm (thinner 1 mm isotropic 3D for volumetric/tumor/pituitary work)
Gadolinium dose 0.1 mmol/kg IV; dynamic thin-section acquisition for pituitary microadenoma
Add MRA/MRV, perfusion, or spectroscopy as clinically indicated

Systematic Review

Assess gray-white differentiation, sulcal and ventricular size, and midline shift/herniation
Review each lobe, deep gray nuclei, and posterior fossa/brainstem systematically
Evaluate FLAIR for periventricular, juxtacortical, and infratentorial signal abnormality
Interrogate DWI/ADC for restricted diffusion (ischemia, abscess, hypercellular tumor)
Scrutinize post-contrast sequences for parenchymal, leptomeningeal, dural, or ependymal enhancement
Check the sella, cavernous sinuses, orbits, IACs, and craniocervical junction
Review SWI for microbleeds, hemorrhage, and mineralization
Inspect the extracranial soft tissues, paranasal sinuses, mastoids, and calvarium

Key Findings & Significance

Ring-enhancing lesion with central diffusion restriction suggests pyogenic abscess versus necrotic tumor
Periventricular ovoid FLAIR lesions perpendicular to ventricles (Dawson fingers) indicate demyelination
Restricted diffusion in a vascular territory signifies acute infarction
Homogeneous dural-based enhancing mass with a dural tail favors meningioma
Leptomeningeal enhancement suggests infectious, inflammatory, or carcinomatous meningitis
Mesial temporal/limbic T2-FLAIR hyperintensity raises herpes or autoimmune encephalitis
Sellar mass with delayed enhancement relative to gland suggests pituitary adenoma
Symmetric hippocampal atrophy supports Alzheimer-type neurodegeneration

Differential Considerations

Ring-enhancing lesions: metastasis, glioblastoma, abscess, demyelination (tumefactive), subacute infarct, resolving hematoma
Multiple T2 white matter lesions: MS, small vessel ischemia, migraine, vasculitis, ADEM, Lyme
Intra-axial mass: primary glioma, metastasis, lymphoma, tumefactive demyelination
Extra-axial mass: meningioma, schwannoma, metastasis, dural metastasis, hemangiopericytoma
Restricted diffusion: acute infarct, abscess, epidermoid, hypercellular tumor, acute demyelination
Sellar/suprasellar lesion: pituitary adenoma, craniopharyngioma, Rathke cleft cyst, meningioma, aneurysm

Pearls & Pitfalls

Always correlate enhancement with DWI/ADC to distinguish abscess from necrotic tumor
FLAIR is more sensitive than T2 for cortical and periventricular lesions but prone to CSF flow artifact
Post-contrast FLAIR increases sensitivity for subtle leptomeningeal disease
Do not mistake normal enhancing structures (pituitary, choroid plexus, vessels, dural sinuses) for pathology
Motion and susceptibility artifacts (dental, postoperative) can mimic or obscure lesions; review all planes
In suspected microadenoma, dynamic timing is critical as lesions are only transiently hypoenhancing
Delayed enhancement after high-dose or double-dose gadolinium increases metastasis conspicuity

Structured Report

State the clinical indication, comparison studies, and technique including contrast dose
Describe lesion location, size, signal characteristics, diffusion, enhancement pattern, and mass effect
Report presence/absence of hemorrhage, herniation, midline shift, and hydrocephalus
Comment on white matter burden, atrophy pattern, and incidental extracranial findings
For MS, quantify new/enlarging and enhancing lesions relative to prior studies
Impression: succinct diagnosis or ranked differential with recommended follow-up or correlation
Flag urgent findings (acute infarct, hemorrhage, herniation, abscess) and communicate directly

References

ACR-ASNR Practice Parameter for the Performance of MRI of the Brain
ACR Appropriateness Criteria (headache, seizure, dementia, focal neurologic deficit)
Thompson et al., 2018 Revised McDonald Criteria for MS diagnosis (Lancet Neurology)
Osborn's Brain: Imaging, Pathology, and Anatomy, 3rd edition
RadioGraphics review articles on intracranial ring-enhancing lesions and CNS infection

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

Brain MRI with Contrast

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References