Home Health A-Z What is an MRI (Magnetic Resonance Imaging)? Why is MRI Done?

What is an MRI (Magnetic Resonance Imaging)? Why is MRI Done?

Verified By Apollo General Physician December 16, 2020 11256 0
What is an MRI (Magnetic Resonance Imaging) Why is MRI Done

An MRI (Magnetic Resonance Imaging) is a test used for diagnosing several medical conditions. It is an imaging test which means that it can be used to take a closer look at what is happening inside the body. The test can be used to look at bones, muscles, brain matter, joints, arteries, and more. An MRI is one of the least harmful tests available and is used by doctors the world over to make an accurate diagnosis and treatment plans.

How does MRI work?

An MRI uses powerful magnets to produce a strong magnetic field. When a person is placed in an MRI machine, the strong magnetic field forces the protons in their body to align with the field. Sensors in the machine can detect the rate at which the protons move and create an image. Different tissues in the body have molecules that move at different rates. A trained radiologist can distinguish the  type of tissue that is shown up on the images.

What is an MRI used for?

An MRI is usually prescribed by a doctor to get a closer look at what is happening inside the patient’s body. It is particularly good at giving insight into the soft tissues and the nervous system. It can be done for  any part of the body and is used to diagnose conditions, look at the extent of a condition, see if the patient is responding well to treatment, or to understand the extent of an injury. An MRI is crucial for imaging the nervous system and find conditions that include the following:

  • Brain injury
  • Stroke
  • Cancer
  • Damage to blood vessels
  • Multiple Sclerosis or MS
  • Problems with the inner ear
  • Assess the spinal column and other joints for injuries , degeneration etc
  • Problems with the eye

When an MRI is prescribed for the heart and the circulatory system, it can look for the following:

  • Heart disease
  • Structure of the heart and any related abnormalities
  • Blockage in blood vessels
  • Extent of the damage caused by a heart attack

An MRI of the bones and musculoskeletal system can detect the following:

  • Cancer
  • Damaged joints
  • Infection of the bones
  • Extent of injuries to the spinal column
  • Damage to the nerves in the spine

Other organs an MRI is used for include:

  • Kidneys
  • Liver
  • Breasts
  • Pancreas
  • Ovaries
  • Prostate

A functional MRI or fMRI is used to map the functional aspects of the brain. It visualizes the flow of blood in the brain to see which parts of the brain are activated when doing certain activities. After the brain is affected by trauma caused by either an injury or a disease like a stroke, it is crucial to know if the brain is functioning to its full capacity as it is supposed to. It can also detect if a tumor is blocking blood flow to the brain. These tests are crucial for planning the right treatment for any condition affecting the brain.

What are the risks of an MRI?

Getting an MRI is a relatively safe option. In fact, it is one of the safest imaging tests available. That being said, there are certain risks involved with the test for people with particular conditions. Women in their first trimester of pregnancy should avoid getting an MRI since this is when the fetus develops its organs.

Some MRI tests use a contrast dye for better imaging. However, few people can have an allergy to the dye. If you are allergic, please inform your doctor and the lab technician well in advance. This type of MRI should not be administered on people with advanced kidney disease either.

An MRI will not be prescribed to patients who have the following conditions:

  • Patients with a pacemaker or defibrillators, though now there are MRI friendly pacemakers available
  • People with cochlear implants

How do I prepare for an MRI?

Your doctor will ask you for a full medical history before prescribing an MRI test. In any case, you must let them know if you have any of the following conditions:

  • Kidney or liver disease
  • Recent surgeries
  • Food or medical allergies or asthma
  • Pregnancy

Since an MRI machine is essentially a large and powerful magnet, no metals will be allowed in the imaging room. You must inform your doctor if you have any of the following:

  • Cochlear implants
  • Body piercings
  • Drug pumps
  • Insulin pump
  • Implanted nerve stimulator
  • Artificial heart valve
  • Pacemakers or defibrillators
  • Metal fragments
  • Pins or screws used in surgery
  • Metal joints or limbs
  • Metal fillings in dental work
  • Tattoos

On the day of the MRI test, wear loose and comfortable clothing without any metal zippers or clasps. You might even be asked to wear a hospital gown for the test instead of your own clothes.

Here is the checklist of all the items you must make sure you do not carry into the imaging room:

  • Mobile phone
  • Dentures
  • Eyeglasses
  • Coins
  • Underwire bra
  • Keys
  • Watch

What does the MRI machine look like?

There are two types of MRI machines – the closed type and the open type. The closed type is the most commonly used MRI machine. It is a large cylindrical machine with a table going through the center. You will be asked to lie on the table and the part of your body that is to be scanned will be positioned within the cylinder. The cylinder contains the magnets that form the core technology of the MRI machine. You will have to lie completely still as the machine scans your body. Otherwise, the images produced will be blurry.

The open type of MRI machine is used in case of patients who cannot fit in the typical type or those who have claustrophobia and cannot be in the machine for too long. However, it is important to note that the open MRI machine does not produce as high a quality of images as the typical closed MRI machine.


An MRI is used for a range of  reasons including diagnosing diseases and checking if the body is responding to treatment. It is one of the safest imaging tools available in the medical industry. The readings of an MRI can be read by specialized radiologists. If you have been asked to get an MRI, visit a reputed hospital or diagnostic lab for the test.

Call 1860-500-1066 to book an appointment

Frequently Asked Questions (FAQs)

1.      What happens during an MRI?

An MRI scan takes anywhere from 20 to 90 minutes, depending on the body part required to be scanned. You may or may not  be injected with a contrast dye depending on the scan. The machine will make a loud thumping noise for which you can ask for earplugs.

2.      Can I go home immediately after an MRI?

There is no problem with you leaving the diagnostic lab immediately after your MRI. In case you have been given a drug to help you relax during the scan, you should ask someone to drive you home.

3.      Are there any side effects to getting an MRI Scan?

Some people might be allergic to the contrast dye used in MRI scans. However, this is very rare and your doctor will check to make sure you are not allergic prior to the scan. References:

Verified By Apollo General Physician

Our expert general medicine specialists verify the clinical accuracy of the content to deliver the most trusted source of information, making the management of health an empowering experience.

Quick Appointment



Book ProHealth Book Appointment
Request A Call Back X