CT and MRI brain imaging
Choosing CT or MRI, reading a CT head in order, what each MRI sequence shows (DWI and ADC, FLAIR, SWI, contrast), how blood ages on CT, ring-enhancing lesions, contrast and MRI safety, and pregnancy.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- CT is fast and everywhere. It is the first test for acute stroke, head injury, suspected haemorrhage and the drowsy patient.
- MRI is better for nearly everything else: early and posterior fossa infarcts, demyelination, tumour, infection, encephalitis and epilepsy work-up.
- Know what each MRI sequence shows. DWI, FLAIR, SWI and post-contrast T1 answer most exam questions.
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Sources
- Australian and New Zealand Living Clinical Guidelines for Stroke ManagementAU/NZStroke Foundation, Living guideline, updated continuously
- Use of intravenous gadolinium-based contrast media in patients with kidney disease: consensus statements from the American College of Radiology and the National Kidney Foundation (Weinreb JC et al. Radiology 2021;298:28-35)American College of Radiology and National Kidney Foundation, 2021
- Use of intravenous iodinated contrast media in patients with kidney disease: consensus statements from the American College of Radiology and the National Kidney Foundation (Davenport MS et al. Radiology 2020;294:660-8)American College of Radiology and National Kidney Foundation, 2020
- Guidelines for diagnostic imaging during pregnancy and lactation (Committee Opinion 723)American College of Obstetricians and Gynecologists, 2017
- The Canadian CT Head Rule for patients with minor head injury (Stiell IG et al. Lancet 2001;357:1391-6)The Lancet, 2001
- Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteriaMontalban X et al., Lancet Neurology 2025;24(10):850-865, 2024 (published 2025)
- MRI-guided thrombolysis for stroke with unknown time of onset (WAKE-UP) (Thomalla G et al. N Engl J Med 2018;379:611-22)New England Journal of Medicine, 2018
- Last updated
- 14 November 2026
What changed
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