Would mri or ct show dementia ar alzheimers?

Sometimes: Head ct and MRI can show shrinkage in certain brain areas, if that is extensive enough. However. Deterioration of brain function in the form of dementia -- including alzheimer's -- develops and impacts the person's behavior long before physical effects show up on ct or MRI scans. These scans would be only part of a workup for possible dementia, not the whole of it.

Not exactly: Imaging of the brain is recommended primarily to rule out reversible causes of dementia; alzheimers per se is associated with brain atrophy, but this can also occur as we age or in other conditions; an imaging study may show vascular events but this too may not correlate cleanly with th esxs.