MRI vs. Cat Scan

I went to a minor emergency for severy stomach pain and they did an x-ray but they were not sure if what they were seeing was my intestines or a mass. The want me to go for a cat-scan. Why would they recommend a cat scan with radiation as opposed to an MRI?

In Question 112

[coughting]

This is the normal next test.  The cat scan with radiation should show them what they need to know.  Also, they may do a ultrasound.
Good luck and let us know how things turn out.

I have chrons and my small intestines were in a wad so it also felt like a mass to the dr.  We did may cat scans and ultrasounds many different tests but never a MRI.  This is how the chrons was finally found.