What is the difference in a CT and a MRI?

CT and MRI scanners and images can look very similar, but the equipment used to perform the scans is completely different.  CT uses ionizing radiation just as with a routine X-ray, while MRI uses a magnetic field. Depending on the reason for your imaging exam, one may be preferred over the other, or sometimes both may be necessary. CT scans take less time than MRI scans; therefore, claustrophobia is not usually a problem.