The short answer
An MRI uses a powerful magnet and radio waves, not radiation, to take detailed picture slices of your body that can show where tumors may be. You lie still on a table that moves into a long chamber. The machine makes loud thumping and rhythmic beating noises. Sometimes a contrast dye is injected into a vein to make tumors show up more brightly.
An MRI uses a powerful magnet and radio waves to take pictures of your body in slices.
The slices are combined into detailed images that can show where tumors may be.
You lie still on a table that is pushed into a long chamber surrounding part or all of your body.
The MRI machine makes loud thumping noises and rhythmic beats while it works.
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The full explanation.
The short version
An MRI can sound intimidating before you have had one, mostly because of the noise and the idea of lying inside a machine. Once you know what is actually happening, it is easier to feel ready for it. An MRI uses a powerful magnet and radio waves — not radiation — to take pictures of your body in slices, which are then combined into detailed images that can show where tumors may be.
How an MRI is different from other scans
Unlike a CT scan or an x-ray, an MRI does not use radiation. Instead, it relies on a strong magnet and radio waves to build its pictures. This is one reason your doctor may choose an MRI for certain parts of the body — the detail it can capture is especially useful for seeing soft tissue clearly.
Before the scan
Because an MRI uses a powerful magnet, your care team will ask you questions and give you instructions to prepare, and you will likely change into a gown and remove anything metal. Ask your team ahead of time exactly what to expect for your particular scan.
During the scan
You lie still on a table, and the table is pushed into a long chamber that surrounds part or all of your body, depending on what area is being imaged. Staying still is important, since the machine is building detailed pictures over the course of the scan.
While the machine works, it makes loud thumping noises and rhythmic beats. This is completely normal — it is simply the sound of the magnet and the machine doing its job, not a sign that anything is wrong. Many people find it helpful to know ahead of time how loud it will be, so the noise does not come as a surprise.
About the contrast dye
For some MRIs, a special dye called a contrast agent is injected into your vein before or during the exam. This dye helps tumors and other areas show up more brightly in the pictures, giving your care team clearer information. Not every MRI requires contrast — your doctor will let you know if yours does.
Getting through the noise and stillness
Lying still inside a chamber for a period of time, with loud noises happening around you, can feel like a lot to manage. It can help to know in advance roughly how long your scan will take and to ask your team about anything they offer to make the experience more comfortable, such as talking to you through the process. Some people find it helps to close their eyes and focus on breathing steadily.
After the scan
Once the scan is complete, you can usually resume your normal activities unless your care team tells you otherwise. If you had contrast dye, ask whether there is anything specific to do afterward.
Questions for your team
Before your appointment, it is reasonable to ask whether you will need contrast dye, roughly how long the scan will take, and what part of your body will be inside the machine. Knowing these details ahead of time can make the whole experience feel far less unfamiliar.
Words to know
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Common questions
▸Will an MRI be loud?
Yes. The MRI machine makes loud thumping noises and rhythmic beats while it takes pictures. This noise is a normal part of how the machine works.
▸What does an MRI actually do?
An MRI uses a powerful magnet and radio waves — not radiation — to take pictures of your body in thin slices. Those slices are combined into detailed images that can show where tumors may be.
▸What is the machine like during the scan?
You lie still on a table that is pushed into a long chamber that surrounds part or all of your body, depending on what area is being imaged.
▸Will I need an injection for my MRI?
Sometimes. A special dye, called a contrast agent, may be injected into your vein before or during the exam to make tumors show up more brightly in the pictures. Not every MRI requires this.
Questions to ask your doctor
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Your next step
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