Both CT scans and MRIs (Magnetic Resonance Imaging) are medical imaging tests, but they have different principles and uses. CT scans use x-rays to create detailed images of the body's internal structures, including bones, organs, and soft tissues. MRI, on the other hand, uses a strong magnetic field and radio waves to create detailed images of the internal structures of the body without the use of ionizing radiation. CT scans are generally faster and easier to use, but MRI scans are better suited for evaluation of soft tissues such as the brain, spinal cord, and joints.