Difference between CAT scans and MRI scans?

[policywonk]

A friend of mine has been having some unpleasant symptoms for a couple of weeks - headaches, heaviness across the eyes, some weakness on her right side, pains in the back of her neck. The GP sent her off for an MRI, which has been done. The hospital has now contacted her with an appointment for a CAT.

Does anyone know what might have been ruled out/in by an MRI? What does a CAT see that an MRI doesn't?

Ta x

A MRI is better at looking at the difference between the tissues, whereas a CT is better at looking at the structure of the anatomy and the blood flow/arteries if this makes sense. There's no radiation with a MRI so they tend to do this first. A MRI brain is really good at picking up lesions/scaring (ie, for MS) as they show up differently due to the change in pathology. A CT scan is sometimes done after to ensure that there's no abnormalities that the MRI didn't pick up. They can also pick up problems with the blood flow into the brain with a CT. Hope this helps.

Thanks v much Belle and Len

CT uses Xrays - it's very good at seeing bone, but can't see subtle differences in soft tissue. They can inject contrast to look at the blood vessels.

MRI uses a big magnet and radiofrequency waves and are fabulous for looking at tiny differences in soft tissues as they pick up teeny differences in how stiff the tissue is, and in how much water is in them.

So, they are complementary to each other - MRI can see things CT can't and vice versa.
I guess they may be wanting to do a contrast enhanced CT in this case