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Magnetic Resonance Imaging (MRI)

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5 min read


MRI is an advanced diagnostic tool that is highly beneficial. Read this article to know more.

Written by

Dr. Lochana .k

Medically reviewed by

Dr. Mounica Kavikondala

Published At February 4, 2021
Reviewed AtSeptember 1, 2022

What Is an MRI Scan?

MRI refers to the Magnetic Resonance Imaging procedure. It serves as a diagnostic tool for visualizing and imaging the different organs and tissues of the body. This method uses a high energy magnetic field and radio waves that are created with the help of a computer. The specialty of MRI is the ability to produce three-dimensional images. These three-dimensional images can be visualized from various angles. It is a harmless procedure, and most doctors will recommend a magnetic resonance imaging scan over a computed tomography scan. The average time taken for an MRI procedure to complete is about 20 to 60 minutes. If there is any disruption in the images, the patient will be called again for the repetition of the procedure.

How Does MRI Work?

Magnetic resonance imaging systems take help from radio waves and magnetic waves. The computer is of additional support to develop a cross-sectional and detailed image of internal structures and organs. The working of magnetic resonance imaging is discussed below.

The functioning of the magnetic resonance imaging scanner requires two magnets that are highly powerful. These magnets are inevitable components of the equipment. Our body contains a large number of water molecules. These water molecules are made up of both hydrogen and oxygen. A smaller particle called proton is present in both the hydrogen and oxygen molecules. These protons serve as a magnetic system that is highly responsive to the magnetic field created by the scanner. The randomly arranged water molecules of the body change in a particular direction after it gets exposed to the first magnet. The second magnet changes the alignment of the hydrogen molecules. The patient would not feel any of the changes happening in the body during the scan.

What Are the Uses of MRI Scans?

MRI scan helps in the examination of tumors, cysts, or any other pathological condition in the human tissues. These might include the following:

  • Internal Organs:

    • Prostate.

    • Kidneys.

    • Liver and bile ducts.

    • Pancreas.

    • Spleen.

    • Ovaries.

    • Uterus.

  • Blood Vessels and Heart:

    • Blockage in the blood vessels.

    • Structural alterations in the aorta such as dissections or aneurysms.

    • Heart-related disorders like a heart attack.

    • The functioning of the heart.

    • The thickness of the walls of the heart.

    • Alterations in the size of the heart valves.

  • Brain and Spinal Cord:

    • Brain injury from trauma.

    • Disorders of the eye and inner ear.

    • Aneurysms of cerebral vessels.

    • Spinal cord disorders.

    • Multiple sclerosis.

    • Tumors.

    • Stroke.

  • Bones and Joints:

    • Any abnormalities in the spine.

    • Infections in the bone.

    • Tumors of the soft tissues and the bones.

    • Traumatic injuries in the cartilage and ligaments.

  • Breast:

    • A mammography procedure is done along with an MRI to detect breast cancer.

What Are the Types of MRI Scans?

There are two types of MRI scans. They are:

  1. Open MRI: In open MRI, all four sides of the patient are open, and this might make them feel less enclosed. It is suitable for patients with claustrophobia. The time consumption is relatively higher. But, this procedure is more friendly for children.

  2. Closed MRI: An MRI scan that is performed in a specific space is known as closed MRI. Closed MRI can produce a high-quality image when compared to the open MRI. The imaging procedure can be completed faster. But, since it is performed in a closed environment, the patient's level of anxiety increases. This method is also associated with an increased level of noise.

Are All Patients Eligible for an MRI Scan?

All the patients are not eligible for an MRI scan. There are several contraindications associated with magnetic resonance imaging. If you come under any of the following categories, then it is essential to get an opinion from your doctor before going for an MRI scan.

  • Pregnancy: As much as possible, MRI should be avoided in pregnant women during the first trimester, but it is not contraindicated. Doctors do recommend MRI scans in the later part of the second and the third trimester. Special care should be given to these patients.

  • Pacemaker: A pacemaker is a tool that is placed on the abdomen or the chest to regulate the rhythms of the heart. It is made up of metal, and such materials are not advisable for an MRI procedure. It is also not possible to remove the pacemaker just for the sake of diagnosis with an MRI. In such cases, it is better to go for alternative diagnostic methods.

  • History of Kidney Problems: One of the life-threatening complications of magnetic resonance imaging is nephrogenic systemic fibrosis. Therefore, patients who are having problems associated with kidneys have refrained from MRI.

  • Claustrophobia: Claustrophobia is a condition in which the patient feels anxious about closed and non-ventilated environments. Since the MRI scan is carried out in an enclosed room, these patients should be exposed to such diagnostic procedures without the prior intake of anti-anxiety medications.

  • Dental Implants: Dental implants are prosthesis that compensates for the tooth that is lost. It is also a metal piece that might interfere with the results of the MRI scan. For this purpose, the patients who have dental implants are not advised to go for this procedure.

  • Allergy to Iodine or Gadolinium: Certain MRI procedures might require the usage of contrast dyes like iodine or gadolinium. All the patients would not have compatibility with these dyes. People who are allergic to them are limited from getting exposed to MRI.

In addition to these, people with the following criteria are also restricted from MRI procedures.

  • Artificial heart valves.

  • Cochlear implants.

  • Vascular stent or stent-graft.

  • Bullet wounds.

  • History as a metal worker.

  • Dorsal column stimulators.

  • History of diabetes.

  • Other health conditions.

  • Neurostimulators (TENS-unit).

  • Skin tattoos.

  • Aneurysm clips.

How to Prepare a Patient Before an MRI?

The patient is asked to remove all the rings, earrings, belts, watches, and other metallic gadgets outside the scanning room. The patient will be asked to remove their clothing and change into the hospital gown. The patients should consume regular medications before the scan. The patient can eat well before the procedure and does not require any fasting condition.

In some conditions, the patient will be given contrast material in the form of a liquid to get more precise visibility of the tissues. The patient will be made to lie down on a scanning table. In addition to this, headphones or earplugs will be provided to avoid the scanner's unnecessary sounds. Children are made to listen to soft music in headphones to ease their anxiety.

During the scanning procedure, the patient will be asked to stay still without any movements. If the patient changes their position during the scan, then there would be a distortion of the images. At a certain point in time, the patient is also asked to hold their breath.

What Are the Side Effects of an MRI Scan?

The common side effects associated with MRI scan are:

  • Allergic reactions to the contrast dyes.

  • Headache.

  • Pain at the injection site.

  • Nervousness.

  • Dizziness.

What Is the Advantage of an MRI Scan Over a CT Scan?

When soft tissues are concerned, both MRI and CT scans are helpful. But, magnetic resonance imaging is beneficial in providing more precise and detailed images of the soft tissues. The risk associated with MRI is relatively low compared to CT scan. MRI can also produce clear pictures of bony structures also. CT scan requires the use of X-rays and might not be suitable for some patients. This problem is overcome by magnetic resonance imaging.

What Are the Disadvantages of an MRI Scan?

The disadvantage associated with an MRI scan are:

  • The cost of an MRI scan is very high.

  • A minor movement might produce a blurry image.

  • Harmful for patients with metallic devices.

  • The presence of foreign matter in the body can cause artifacts.

  • The imaging time is longer.

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Frequently Asked Questions


What Is the Principle Mechanism of Magnetic Resonance Imaging?

Magnetic resonance imaging uses powerful magnets to produce strong magnetic fields that cause the atoms in the body to align in the same direction with the field. Then, radio waves are sent from the MRI machine, which moves the atoms out of their original position. As the radio waves are turned off, the atoms return to their original position, sending the radio signals back and creating the image.


What Can Be Diagnosed With an MRI Scan?

MRI scan can be used to diagnose various anomalies in the body, which include the following:
- Tumors (cancerous and non-cancerous).
- Joint injury or diseases.
- Soft tissue injuries such as damaged ligaments.
- Spinal cord injury or disease.
- The disease of internal organs such as the heart, brain, and digestive organs.


What Is the Use of Magnetic Resonance Imaging?

Magnetic resonance imaging is a non-invasive imaging technique. This helps create a detailed three-dimensional anatomical image of the inside of the body. It is mostly used for disease detection, diagnosis, and treatment planning and involves less radiation exposure.


What Are the Components of MRI?

Magnetic resonance imaging consists of four components which include the following:
- Superconducting coils form the main magnet.
- Gradient coils.
- Radiofrequency (RF) coils.
- Computer systems.


Is It Okay to Drink Water Before the MRI?

On the day of the MRI, the patient can eat, drink or take any medications as usual unless the healthcare professional advises not to do so. It usually depends upon the situation. Sometimes, the patient will be told to drink plenty of water before the scan or not to eat or drink anything for up to four hours before the scan.


Which One Is Better, CT or MRI Scan?

CT (computed tomography) and MRI (magnetic resonance imaging)scans can help view internal body structures. However, a CT scan is much faster and can provide pictures of organs, tissues, and skeletal structures. But the images are not as effective as MRI scans. In addition, patients with metal implants or pacemakers can not go for an MRI scan due to the use of powerful magnets and have to opt for a CT scan.


What Should Not Be Done Before MRI?

A person can eat and normally drink before the MRI scan and take their medicines as usual unless advised by the healthcare provider not to do so. Moreover, the patient will be asked to remove the following things before going for the scan, such as:
- Jewelry.
- Eyeglasses.
- Hearing aids.
- Watches.
- Wigs.
- Hairpins.
- Dentures.
- Underwire bras.
- Avoid using cosmetics that contain metal particles.


How Long Does an MRI Scan Take?

A single scan MRI may take up to a few seconds or ten minutes. The patient may be asked to hold their breath during short scans. The total scan can take up to 15 to 90 minutes, depending upon the size of the area to be scanned and the number of images required.


What Are the Most Commonly Advised MRI Scans?

The MRI scans are mainly advised for diagnostic purposes, which include the following:
- Functional MRI (FMR) scans to test brain activity.
- Cardiac MRI to get detailed images of the heart.
- MRI of the breast in patients at high risk for breast cancer.
- Magnetic resonance venography (MRV) combined with contrast dye to get clear images of internal organs and other structures inside the body.


What Chemicals Are Used in MRI Contrast Dye?

Magnetic resonance imaging (MRI) contrast agents are the pharmaceuticals widely used in MRI scans. This includes gadolinium-based MRI contrast agents (GBCAs), most commonly used as contrast dyes as it highlights the veins that appear translucent and show up well in images.


What Is the Most Common Injury in MRI?

The most common injury associated with MRI is due to the presence of metal in the body. The movement of metal within the body during the scan can cause heat and discomfort. In rare cases, metal can also shift and cause physical damage, such as a tear in the skin. However, such incidents are rare and can be prevented by informing the radiologic technologist about the presence of metal in the body or a medical device before an MRI scan.


How Much Time Does a Full Brain MRI Take?

A full brain MRI may take up to 30 minutes to an hour. The timing may be increased if contrast dyes are also used. However, the healthcare provider can tell the exact time range depending on the reason for the scan.


Will I Get My MRI Results Immediately?

Typically, the results of an MRI scan are not available immediately. The images from the MRI scan need to be reviewed and interpreted by a radiologist, which usually takes some time. The time it takes to get the results can vary depending on the facility, the type of exam, and the case's complexity. In some cases, the results may be available the same day or within a few hours, while in others, it may take a day or two.
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Dr. Lochana .k
Dr. Lochana .k



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