Updated November 5, 2026 · By the MRIScanNearMe.com Team
Quick answer: MRI uses magnets and radio waves, and CT uses X-rays. MRI involves no radiation and shows soft tissue, joints, the brain and the spinal cord especially well. CT is quicker, usually taking a few minutes according to MedlinePlus, so it is often used for injuries, bleeding and the chest, abdomen and pelvis. Your doctor chooses based on what needs answering.
If your doctor mentioned a scan, you may be wondering why it is an MRI and not a CT, or the other way around. Both create detailed pictures of the inside of your body, but they work differently and answer different questions. Here is how they compare, in plain language.
What is the difference between an MRI and a CT scan?
The main difference is how the pictures are made. An MRI uses magnets, radio waves and a computer. A CT scan uses X-rays, with an X-ray tube that rotates around your body as you pass through a large donut-shaped machine.
That difference shapes almost everything else about the two tests:
| MRI | CT scan | |
|---|---|---|
| How it works | Magnetic field and radio waves | X-rays taken from many angles |
| Radiation | None | Yes, kept as low as possible |
| Scan time | Varies by body part; often longer | Usually a few minutes |
| Often used for | Brain, spinal cord, joints, ligaments, tendons | Fractures, internal injuries, chest, abdomen, pelvis |
| What you notice | Loud noises; earplugs or headphones offered | Whirring sounds |
| Contrast dye, if needed | Often gadolinium-based | Often iodine-based |
When is an MRI usually the better choice?
An MRI is usually the better fit when your doctor needs a close look at soft tissue. The National Institute of Biomedical Imaging and Bioengineering (NIBIB) says MRI is particularly well suited to the non-bony parts of the body, and that it is often used for knee and shoulder injuries.
Common reasons to order an MRI include:
- Brain and spinal cord questions. Mayo Clinic calls MRI the most frequently used imaging test of the brain and spinal cord.
- Joint injuries. Torn cartilage and ligaments are typical examples, and RadiologyInfo notes that knees and shoulders can often be better evaluated with MRI than with CT.
- Back problems. Disk problems and spinal cord conditions are on Mayo Clinic's list. If back or joint pain is what led you here, you can also find a pain specialist through PainDocNearMe.com.
- Repeat imaging. Because there is no radiation, NIBIB says MRI is the modality of choice when frequent imaging is required.
If an MRI is on your calendar, our MRI preparation guide walks through what to do beforehand.
When is a CT scan usually the better choice?
A CT scan is often the better fit when speed matters or when the question involves bone or the torso. RadiologyInfo describes CT as one of the fastest and most accurate tools for examining the chest, abdomen and pelvis, and says it can reveal internal injuries and bleeding quickly in emergencies.
NIBIB adds that CT is particularly useful for complex bone fractures, severely eroded joints and bone tumors. It can also show lung tumors, and blood clots in the lungs or those leading to stroke. So if you arrive at an emergency department after an accident, CT may well be the first scan you get.
Is an MRI safer than a CT scan?
Both are widely used, and neither is automatically the safer choice for everyone. The risks are simply different.
CT uses ionizing radiation, at levels higher than a standard X-ray. The FDA says this may cause a small increase in lifetime cancer risk, while RadiologyInfo says there is no conclusive evidence that the small amounts from a CT scan cause cancer. Your doctor weighs that against the value of a clear answer.
MRI has no radiation, but its strong magnet matters. Metal objects or implants can interfere with the scan and may be unsafe, so you will be asked about them first. RadiologyInfo says most orthopedic implants pose no risk, though the magnet may cause some implanted devices to malfunction. By contrast, an implanted device will not prevent you from having a CT.
Comfort differs too. MRI usually means more time in a tunnel-like machine, plus loud noise. If tight spaces worry you, our guide to open and wide-bore MRI for claustrophobia explains your options.
If you are pregnant or might be, tell your provider before either test. RadiologyInfo says doctors do not generally recommend CT for pregnant women unless medically necessary. It also says a doctor may use body MRI to monitor a baby safely.
Why would a doctor order one test and then the other?
Because each test answers a different question. RadiologyInfo says that MRI can sometimes identify disease more accurately than other methods in soft tissue, while CT is quick and shows bone, soft tissue and blood vessels together. A doctor might start with whichever test is fastest or most likely to help, then add another if more detail is needed.
Contrast is a separate decision for each test. If yours includes it, this guide to MRI with or without contrast explains what changes. Cost can also shape the choice, since RadiologyInfo says an MRI typically costs more. Our guide to what an MRI costs without insurance covers what to ask about pricing.
Frequently asked questions
Which shows more detail, an MRI or a CT scan?
It depends on the body part. MRI is especially suited to soft tissues such as the brain, spinal cord, ligaments and tendons. CT is strong on bone and can show bone, soft tissue and blood vessels at the same time.
Does an MRI or a CT scan take longer?
An MRI often takes longer. MedlinePlus says a CT scan usually takes a few minutes, though some last up to 30 minutes. RadiologyInfo says an MRI may take more time than other imaging exams, and the length depends on the body part.
Can I have an MRI if I have metal in my body?
Often yes, but it depends on the device or implant. RadiologyInfo says most orthopedic implants pose no risk, while some implanted devices can malfunction in the magnetic field. Tell your care team about any metal or device before your scan so they can check it.
Is an MRI more expensive than a CT scan?
Generally yes. The National Institute of Biomedical Imaging and Bioengineering says MRI is more expensive than X-ray or CT imaging. What you pay depends on your insurance, the facility and the body part, so ask for a price before you book.
Can I ask for an MRI instead of a CT scan?
Yes, you can ask, and it is a reasonable conversation to have. Your doctor can explain which test fits your symptoms and whether an MRI would answer the same question.
Find an MRI near you
Once your doctor has ordered an MRI, you may be able to choose where to have it done. Browse MRI imaging centers by state to compare locations, or go straight to a state page such as MRI centers in Florida.
Sources: NIBIB: Magnetic Resonance Imaging; NIBIB: Computed Tomography; RadiologyInfo.org: Body MRI; RadiologyInfo.org: Body CT; MedlinePlus: MRI Scans; MedlinePlus: CT Scans; U.S. FDA: Computed Tomography; Mayo Clinic: MRI.
This article is for educational purposes and is not medical advice. Talk with your doctor about which scan is right for you.