CT is a great screening exam because it is cheap, quick and more readily available. MRI is much more specific in diagnosing problems in the brain and has a lot more 'features' that can be added to aid in diagnosis. So generally, everyone gets a CT and then moves on to an MRI if there is an abnormality... or if they fail to find an abnormality when the clinical exam remains abnormal/severe. There are a lot of exceptions... like in little kids, you should always avoid radiation when possible and people will go straight to MRI.
Why is there such a big difference in patient price between a CT and MRI scan?
My doctor told me to have a CT scan done but I am worried about the radiation. I feel that if an MRI was cheaper, then I would have been prescribed an MRI.
The MRI scanner requires more precautions and safeguards (being built around a 1+ tesla magnet), and acquiring images takes more time, thus more human resources.
Edit: to illustrate ris' point (the sibling comment), check this XKCD chart, linked in the article: http://xkcd.com/radiation/
You're confusing CT scans with conventional x-ray images. CT scans deliver the radiation equivalent of hundreds of conventional x-ray images. The radiation dose is high enough to epidemiologically significant (meaning higher cancer rates in people who have been scanned, especially children).
Believe me, I'm not confusing them - I just think it's significantly less risky than the parent does. And yes, there can be higher cancer rates in people who have a _lot_ of CT scans done e.g. because of a serious illness.
I'd rather get that back to me as a percentage compared to a Phone Booth filled with nuclear waste (but only 75% of the way up) while standing 13.43 meters away with the humidity levels at 95%.
