What is the difference between an MRI and a CT scan?
Last updated September 3, 2026.
CT is a fast x-ray-based scan best for bone, lungs, and trauma; MRI uses magnets and radio waves - no radiation - takes longer, and sees soft tissue better. CT takes minutes and handles emergencies; MRI takes 30 to 60 minutes and details the brain, spinal cord, and ligaments. The question being asked decides the tool, and sometimes both are ordered because they answer different questions.
What to do
- Ask what question the scan answers. The choice follows the clinical question, not a ranking of machines.
- Flag metal for MRI. Implants and fragments that are irrelevant to CT can rule MRI out or change the plan.
- Weigh radiation for repeats. One CT is a small risk; a series of them is worth an alternatives conversation.
- Bring prior images. Either way, old scans prevent duplicate new ones.
Related questions
- What happens at an MRI?
- Do CT scans cause cancer?
- Is an MRI safe?
- How much radiation is in a chest X-ray?