Why would basal ganglia stroke show up in mri but not ct?

Different tests: Although MRI and ct are both used to image the brain, they use different techniques to generate images, and are good at different things. Ct is good for acute bleeding in the brain, can be done quickly on arrival, and is able to be done in most centers at any time. Mri is better at looking at small specific areas in the brain especially for basal ganglia stroke.

MRI vs CT Brain: In general ct scans are for bone imaging and MRI scans are for soft tissue imaging. Ct scans are fast in the order of seconds and mris take about a half hour. A skull fracture are best imaged by ct. Mris are best for brain strokes and brain tumors. The exception to this is that strokes that cause bleeding in the brain can be quickly imaged by ct in an emergency, but should be followed by mri.