What is the magnetic resonance imaging scan?
Magnetic resonance imaging (MRI) is a medical imaging technique that uses a magnetic field and computer-generated radio waves to create detailed images of your body’s organs and tissues.
Most magnetic resonance imaging machines are large tubular magnets. When you lie down inside a magnetic resonance imaging machine, the magnetic field temporarily detects water molecules in your body. Radio waves produce these alignment molecules to produce thicker signals, which are used to generate cross-sectional MRI images, such as slices in a loaf of bread.
Your doctor can use this test to diagnose you or to see how well you respond to treatment. Unlike X-rays and computed tomography (CT), MRIs do not use the harmful ionizing radiation from X-rays. The MRI machine can also view 3D images from different angles
Why is magnetic resonance imaging done?
Magnetic resonance imaging is an unpredictable way for your doctor to examine your organs, tissues, and skeletal system. Produces high-resolution images of the inside of the body, helping to identify a variety of problems. MRI is the most widely used imaging test of the brain and spinal cord.
This is often done to help diagnose:
- Cerebral vascular aneurysms
- Defects of the eye and inner ear
- Multiple sclerosis
- Spinal cord defects
- Trauma brain injury
A special type of MRI is functional magnetic resonance imaging (fMRI) of the brain. Produces images of blood flow to certain areas of the brain. It can be used to examine the anatomy of the brain and determine which parts of the brain perform complex functions.
It helps identify important areas of language and movement control in the brain of people who are being considered for brain surgery. Functional MRI can also be used to assess damage from a head injury or disorders such as Alzheimer’s disease.
MRI of the heart and blood vessels
An MRI can be done that focuses on the heart or blood vessels:
- Size and function of the cardiac chambers.
- Thickness and movement of the walls of the heart.
- Damage caused by heart attack or heart disease
- Structural problems such as aneurysms or dissections in the aorta
- Inflammation or blockage of blood vessels.
- MRI of other internal organs
Magnetic resonance imaging can detect tumours or other abnormalities in many organs of the body, including:
- Liver and bile ducts
- MRI of bones and joints
Helps in MRI evaluation:
- Joint abnormalities caused by painful or recurring injuries, such as damaged cartilage or tendons
- Disc abnormalities in the spine
- Bone infection
- Bone and soft tissue tumours
- Breast MRI
MRI with mammography can be used to diagnose breast cancer, especially in women with dense breast tissue or at high risk for the disease.
A special kind of MRI called a functional MRI maps brain activity.
This test looks at blood flow in your brain to see which areas become active when you do certain tasks. An fMRI can detect brain problems, such as the effects of a stroke, or it can be used for brain mapping if you need brain surgery for epilepsy or tumours. Your doctor can use this test to plan your treatment.
What are the risks and side effects of the test?
An MRI is a painless radiology technique that has the advantage of preventing exposure to X-ray radiation. There are no side effects of MRI. The advantages of an MRI are related to its accuracy in detecting structural abnormalities in the body.
Patients with metallic substances in the body should inform their physician or MRI personnel before testing. Metal shavings, materials, surgical clips, or foreign materials (artificial joints, metal bone plates or prosthetic devices, etc.) can significantly distort the images obtained with an MRI scanner.
Patients with cardiac pacemakers, metal implants, or metal chips or clips in or around the eyebrows cannot be scanned with MRI because there is a risk of magnetic metal moving in these areas. Similarly, patients with artificial heart valves, metal ear implants, bullet fragments, and chemotherapy or insulin pumps should not have an MRI.
During the MRI, the patient stays in a closed area inside the magnetic tube. Some patients may experience a feeling of claustrophobia during this process. Therefore, patients with a history of claustrophobia should contact the physician ordering the test, as well as the radiology staff.
A mild sedative may be given before the MRI to reduce this sensation. It is common for MRI personnel to be present during the MRI scan. Also, there are usually ways to communicate with staff (such as the doorbell the patient has) that can be used to contact if the patient cannot tolerate the scan.
Preparation for a magnetic resonance imaging
Before your MRI, you should tell your doctor:
- If there are health problems such as kidney or liver disease
- You recently had surgery
- Have any food or drug allergies or have asthma
- You may be pregnant
Metal is not allowed in the MRI room because the magnetic field from the machine can attract metal. Tell your doctor if you have metal devices that can cause problems during the test. These include:
- Artificial heart valves
- Body piercings
- Cochlear implants
- Drug bombs
- Fillings and other dental work
- Tight nerve stimulation
- Insulin bomb
- Bullet or sharp metal shards
- Metal joints or limbs
- Pacemaker or implantable cardioverter-defibrillator (ICD)
- Pins or screws
If you have tattoos, talk to your doctor. Some veins contain metal.
On the day of the test, wear loose, comfortable clothing that does not have snaps or other metal zippers. You will need to remove your clothing and put on a gown during the test.
Remove all of these before entering the MRI room:
- Mobile phone
- Underwear bra
- If you don’t like confined spaces or are concerned about tests, tell your doctor. You may have an open MRI or need to take medicine to rest before the test.
What can you expect during the test?
The magnetic resonance imaging machine looks like a long, narrow tube with two open ends. Lie on the table you are moving, it will slide into the opening of the tube. A technician will monitor you from another room. You can speak to the person through the microphone.
If you are afraid of enclosed spaces (claustrophobia), you may be given medicine to help you sleep and feel less anxious. Most people pass the test without problems.
The MRI machine creates a strong magnetic field around you, and radio waves are directed towards your body. The procedure is painless. It does not experience magnetic fields or radio waves and there are no moving parts around it.
During an MRI, the inside of the magnet makes repeated bumps, knocks, and other sounds. You can put on earplugs or play music to help block out noise.
In some cases, the contrast material, usually gadolinium, is injected intravenously (IV) into a vein in the hand or arm. The contrast material adds some details. Gadolinium rarely causes allergic reactions.
An MRI scan can last from 15 minutes to more than an hour. It must be still so that movement can blur the resulting images.
During a functional MRI, you may be asked to perform several small tasks, such as pressing your thumb with your fingers, rubbing sandpaper, or answering simple questions. It helps identify the parts of your brain that control these actions.
After an MRI
You can usually go home after magnetic resonance imaging and get back to your normal routine. If you have a medicinal potion to relax, it will remain in the imaging center until you are fully awake. You need someone to drive you home.