MRI Scan: What It Is and What to Expect

What Is an MRI?

An MRI is a noninvasive medical imaging test. This means it does not require surgery and does not enter the body with instruments.

The scanner uses a strong magnet and radio waves to create detailed pictures of nearly every internal structure, including:

• Brain and spinal cord
• Heart and blood vessels
• Joints and muscles
• Internal organs

These images give doctors important information about what is normal and what is not.

How Does an MRI Work?

The MRI machine is usually a large, tube-shaped scanner. Some machines are narrow like tunnels, while others are more open.

Here is how it works in simple terms:

• The machine creates a strong magnetic field around your body.
• This magnetic field causes tiny particles in your body, called atoms, to line up.
• The scanner then sends radio waves that move these atoms out of position.
• When the radio waves stop, the atoms return to their original position.
• As they return, they send signals back to the scanner.
• A computer turns these signals into detailed images.

Because MRI does not use radiation, there is no risk of radiation exposure during the exam.

MRI is especially helpful for studying soft tissues. In many cases, it can show more detail than a CT scan when looking at muscles, organs, or the brain.

Advanced Types of MRI

Over time, MRI technology has improved. Today, there are several specialized types of MRI scans.

Magnetic Resonance Angiography (MRA)

MRA looks specifically at blood vessels and blood flow.

Doctors use it to detect:

• Narrowed arteries
• Aneurysms in the brain
• Blood vessel abnormalities

Functional MRI (fMRI)

Functional MRI studies brain activity.

It shows which part of the brain controls certain functions like speech or memory. During the scan, you may be asked to perform a simple task, such as speaking or moving a finger. This helps doctors identify exact brain areas before surgery or treatment.

Other Specialized MRI Studies

Some exams require special preparation and focus on specific areas, including:

• Breast MRI
• MRI-guided breast biopsy
• Pelvic MRI
• Prostate MRI
• Enterography (for the intestines)

If you need a specialized MRI, you will receive detailed instructions before your appointment.

How to Prepare for an MRI

Most MRI exams require little preparation. However, it is important to follow the instructions given by your medical center.

Eating and Drinking

For most MRI exams, you can eat, drink, and take your medications as usual.

Some specialized exams may have restrictions. Always follow the instructions you receive.

Clothing and Personal Items

You will need to:

• Remove all clothing, including underwear
• Wear a hospital gown
• Remove jewelry, piercings, hairpins, glasses, hearing aids, and removable dental work

Metal objects can interfere with the magnetic field and affect the images.

Tell Your Doctor If You Have:

Because MRI uses a strong magnet, you must inform your doctor if you have:

• A pacemaker
• Artificial heart valves
• An insulin pump or other implanted pump
• Stents, clips, coils, or filters
• Metallic fragments in your body
• A history of bullet wounds
• A job involving metalwork
• Pregnancy or possible pregnancy
• Difficulty lying flat for 30 to 60 minutes

If metal is discovered on the day of your exam and was not reported earlier, the test may be delayed or rescheduled.

What If Contrast Is Needed?

Some MRI exams require contrast dye to make certain tissues easier to see.

If contrast is used:

• An IV line will be placed in your arm or hand.
• You may feel a brief cold sensation, flushing, or a metallic taste.
• These effects usually last only a few moments.

If you have had a previous allergic reaction to MRI contrast, tell your doctor in advance. You may need medication before the exam.

What If You Feel Claustrophobic?

MRI machines can feel narrow. If you feel anxious in small spaces:

• Talk to your doctor before your appointment.
• Anti-anxiety medication may be prescribed.
• You will need someone to drive you home if you take it.

Earplugs or headphones are provided because the machine makes loud clicking sounds during the scan.

What Happens During the MRI Procedure?

An MRI can be done as an outpatient test or during a hospital stay.

Here is what usually happens:

1. You change into a gown and remove all metal items.
2. If contrast is needed, an IV line is placed.
3. You lie on a table that slides into the scanner.
4. Pillows or straps may be used to help you stay still.
5. The technologist operates the machine from another room but can see and hear you at all times.
6. You will receive ear protection because the machine is loud.

During the scan:

• You must lie very still.
• You may hear clicking or tapping sounds.
• You may be asked to hold your breath briefly for certain images.

The scan itself is painless. However, lying still for a long time may cause mild discomfort, especially if you have a recent injury.

When the scan is finished, the table slides out and you are helped off.

What Happens After an MRI?

Most people can return to normal activities right away.

If you received sedatives:

• You must wait until they wear off.
• You cannot drive yourself home.

If contrast was used, contact your doctor immediately if you notice:

• Rash
• Swelling
• Itching
• Difficulty breathing

These reactions are rare but require medical attention.

You should also call your doctor if you notice redness, pain, or swelling at the IV site.

Otherwise, no special care is needed.

When Will You Get Your Results?

A radiologist reviews the images and prepares a report for your doctor.

Results are usually available within a few days, depending on the medical center. Your doctor will discuss the findings and explain the next steps if needed.

Is MRI Safe?

MRI is considered very safe for most people.

It does not use radiation, which makes it safer than some other imaging tests. The main safety concern involves metal objects or implanted devices, which is why detailed screening before the exam is so important.