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What is MRI scan?

A scan of magnetic resonance imaging (MRI) is a common procedure worldwide.

To create detailed images of the organs and tissues within the body, MRI uses a strong magnetic field and radio waves.

Doctors and researchers have continued to develop MRI methods to assist with medical procedures and analysis since its invention. Medicine was revolutionized by the invention of MRI.

Specifically this article looks at MRI scans, how they function and how doctors use them.

Important facts about MRI scanning

  • MRI scanning is a non-invasive and painless procedure.
  • Raymond Damadian created the first MRI full-body scanner, which he nicknamed the Indomitable.
  • The cost of a basic MRI scanner starts at $150,000 but can exceed several million dollars.
  • Japan has the most MRI scanners per capita, with 48 machines for every 100,000 citizens.

What is an MRI scan?

A doctor using MRI scan
MRI scans can produce a detailed image.

An MRI scan produces a accurate, cross-sectional image of internal organs and structures using a large magnet, radio waves and a computer.

Usually the scanner itself resembles a large tube with a table in the middle, allowing the patient to slide in.

An MRI scan is distinct from CT scans and X-rays as it does not use ionizing radiation that is potentially harmful.


MRI scan technology represents a tremendous achievement for the medical world.

Doctors, scientists, and researchers may now use a non-invasive method to explore the inside of the human body in great detail.

The following are examples in which an MRI scanner would be used:

  • anomalies of the brain and spinal cord
  • tumors, cysts, and other anomalies in various parts of the body
  • breast cancer screening for women who face a high risk of breast cancer
  • injuries or abnormalities of the joints, such as the back and knee
  • certain types of heart problems
  • diseases of the liver and other abdominal organs
  • the evaluation of pelvic pain in women, with causes including fibroids and endometriosis
  • suspected uterine anomalies in women undergoing evaluation for infertility

That list isn’t exhaustive at all. The use of MRI technology continues to grow in scope and use.


A person can listen to music in headphones to mask the loud and sometimes alarming sound of the MRI machine.
A person can listen to music in headphones to mask the loud and sometimes alarming sound of the MRI machine.

Upon arrival at the hospital, doctors could recommend that the patient change into a gown.

Since magnets are being used it is important that there are no metal artifacts in the scanner. The doctor will recommend that the patient remove any metal jewelry or accessories that can interfere with the system.

A individual is likely to be unable to have an MRI if they have any metal inside their body, such as bullets, shrapnel or other foreign metallic bodies. Medical devices such as cochlear implants, aneurysm clips, and pacemakers may also be included.

Individuals anxious or worried about nearby spaces should inform their doctor. These medicines may also be given before the MRI to help make the procedure more comfortable.

Often patients may receive an injection of intravenous (IV) contrast liquid to enhance the visibility of a specific tissue appropriate for the scan.

A doctor specialized in medical images, the radiologist will then speak to the patient about the MRI scanning process and answer any questions they may have about the procedure.

Upon entering the scanning room the patient will be helped by the doctor to lie down on the scanner table. By having covers or cushions, staff must ensure that they are as comfortable as possible.

They should have earplugs or headphones to block the scanner’s loud noises. The latter is popular with kids, because they can listen to music during the procedure to relieve any anxiety.

During an MRI scan

The MRI technician will communicate with the patient through the intercom while inside the scanner to make sure they are relaxed. They don’t start scanning until the patient is ready.

Staying still is vitally necessary during the scan. Any motion can interrupt the pictures, just like a camera attempting to capture a moving object. The scanner will bring out loud clanging noises. That would be perfectly normal. Depending on the photos, the person can at times need to hold his breath.

If the patient feels nervous during the treatment, they will use the intercom to talk to the MRI technician and ask for the scan to be halted.

After an MRI scan

The radiologist will review the images after the scan to test if any more are needed. If the radiologist is happy the patient will be able to go home.

The radiologist must write a report for the doctor who requests it. Normally patients are asked to make an appointment with their doctor to discuss the findings.

Side effects

It is highly unlikely for a patient to experience side effects from an MRI scan.

However, in some people the contrast dye can cause nausea, headaches, and pain or burning at the injection point. Similarly, allergy to the contrast material is rarely seen but possible, and can cause hives or itchy eyes. Notify the technician should there be any adverse reactions.

Often people who experience claustrophobia or feel insecure in confined spaces communicate difficulties with an MRI scan.


water molecules
MRI scans work by rearranging water molecules in the body with magnets.

An MRI scanner has two strong magnets in it. These are the most important pieces of equipment.

The human body consists largely of water molecules which consist of atoms of hydrogen and oxygen. An even smaller particle called a proton lies at the core of each atom, which acts as a magnet and is prone to any magnetic field.

The water molecules in the body are usually distributed randomly, but when an MRI scanner is entered the first magnet causes the water molecules to move in one direction, either north or south.

The second magnetic field is then turned on and off in a series of rapid pulses, causing each hydrogen atom to change its orientation when turned on and then turn back quickly when switched off to its original relaxed state.

It generates the magnetic field by transferring electricity through gradient coils, which also causes the coils to vibrate, creating a knocking sound within the scanner.

Although the patient can not feel these changes, they can be identified by the scanner and, in combination with a computer, the radiologist can produce a detailed cross-sectional image.

Functional magnetic resonance imaging (fMRI)

Functional MRI (fMRI) magnetic resonance imaging uses MRI technology to assess cognitive function by measuring blood flow to certain parts of the brain.

In areas where neurons are involved the blood flow increases. This provides an insight into neuronal activity within the brain.

This technique has revolutionized brain mapping, enabling researchers to examine the brain and spinal cord without requiring invasive procedures or injections of drugs.

Functional MRI lets researchers learn about normal, diseased, or damaged brain functions.

For clinical research fMRI is also used. Normal MRI scans are useful to detect tissue structural abnormalities. Nevertheless, an fMRI scan can help detect activity abnormalities.

In short, the fMRI checks what tissues are doing rather than acting like they are.

As such, doctors use fMRI to determine brain surgery risks by defining regions of the brain that are involved in vital functions such as speaking, shifting, sensing, or preparing.

Often, functional MRI may be used to assess the symptoms of cancers, stroke, brain and head trauma, or neurodegenerative disorders such as Alzheimer’s.


How long will an MRI scan take?

MRI scans vary between 20 and 60 minutes depending on which part of the body is examined and how many images are required.

If the images are not clear enough for the radiologist after the first MRI scan, they can specifically ask the patient to undergo a second scan.

I have braces or filings, should I still undergo the scan?

Though the scan does not affect braces and fillings, they can distort those images. That will be addressed in advance by the doctor and technician. If additional images are needed the MRI scan can take longer.

Can I move while I am in the MRI tunnel?

Staying as still as possible is important while in the MRI scanner. The scanner will be blurred by any movement and therefore the images created will be blurry. The MRI technician may allow a short break halfway through the procedure in specially long MRI scans.

I am claustrophobic, what can I do?

The doctor and radiologist should be able to speak about the whole process to the patient and discuss any anxieties. Open MRI scanners for some areas of the body are available in certain places to aid people with claustrophobia.

A person can take medication prior to the test to ease anxiety.

Do I need an injection of contrast before my MRI scan?

A contrast dye can improve diagnostic accuracy by highlighting certain tissues.

Some patients may need to have a contrast agent injected before the scan.

Can I have an MRI scan if I am pregnant?

Unfortunately, the answer isn’t easy. Until the exam, let a doctor know about your pregnancy. Relatively few studies have been performed about the effect of MRI scans on pregnancy. Guidelines published in 2016 have, however, shed further light on the issue.

Doctors usually don’t prescribe comparison content for pregnant women.

In the first trimester MRI scans should be restricted, unless the information is deemed necessary. The MRI scans are healthy at 3.0 tesla (T) or less during the second and third trimesters. The tesla is a measure of magnetic resistance.

The Guidelines also note that first trimester exposure to MRI is not related to long-term effects and do not raise health concerns.