X-ray is quick and cheap and shows bone well. CT is a fast, detailed scan built from X-rays — best for injuries, bleeding and the chest and abdomen. MRI uses magnets rather than radiation and shows soft tissue best — brain, spinal cord, ligaments and joints. More expensive does not mean more appropriate.
People often assume these are a quality ladder, with MRI at the top. They are not. They show different things, and the right one depends entirely on what the doctor is looking for.
Asking for an MRI when a plain X-ray would answer the question wastes money and sometimes finds harmless things that lead to more tests.
The one thing worth knowing before any scan: tell the staff if you are or might be pregnant, and if you have any metal implant, pacemaker or device in your body.
Side by side
| CT scan | MRI | |
|---|---|---|
| How it works | Many X-rays combined by computer into cross-sections | Strong magnets and radio waves — no X-rays |
| Radiation | Yes, more than a plain X-ray | None |
| Best for | Injuries, bleeding in the brain, chest, abdomen, stones, lungs | Brain, spinal cord, ligaments, joints, soft tissue and tumours |
| Time taken | Usually a few minutes | Usually 20 to 45 minutes |
| Noise and space | Quick and open | Loud, and the tunnel is enclosed — difficult if you are claustrophobic |
| Cost in India | Higher than X-ray, lower than MRI | Usually the most expensive of the three |
| Metal implants | Usually fine | Can be unsafe — always declare pacemakers, implants and metal fragments |
| Plain X-ray | Fastest and cheapest; good for bones, chest and obvious fractures | — |
When CT scan is usually the better choice
- An accident or serious injury, where speed matters
- Suspected bleeding in the brain
- Chest, abdominal or kidney stone problems
- When you cannot lie still for long, or have a device that rules out MRI
When MRI is usually the better choice
- Brain and spinal cord problems that are not emergencies
- Ligament, cartilage and joint injuries
- Nerve compression causing arm or leg symptoms
- When avoiding radiation matters, such as in younger patients needing repeat scans
Important
Tell the staff if you are or might be pregnant, and declare any pacemaker, implant, metal fragment or device before an MRI. Also worth asking your doctor: what will this scan change about my treatment? If the answer is nothing, it may not be needed.
This page does not choose for you
Which is right depends on your other conditions, your other medicines and your history. Ask your doctor or pharmacist — and follow what they say over what you read here.