CT . Ct (computed tomography) scans are generated using x-ray radiation and computer processing to create a 3d x-ray image. Mri (magnetic resonance imaging) is a technology that utilizes a large magnetic field to re-orient the body's atoms and cause their nuclei to spin in such a way that an image is created. Both ct and MRI offer high resolution pictures and can create images of any part of the body; but, depending on the particular health condition one may be better suited than the other. The lack of radiation in MRI is the major difference from ct. From the patient perspective, both involve laying still on a flat table inside a "tube" that contains the imaging equipment. The tube is narrower with mri, and the scans are generally longer with mri.