What is an MRI Scan: Purpose, Use, Risks, Benefits, Procedure, Duration, Difference Between MRI and CT

What is an MRI Scan?

An MRI (magnetic resonance imaging) scan is a radiology imaging test which uses radio waves, magnetism, and a computer to generate images of different body structures. This is one of the safest and accurate imaging tests done for diagnosing different diseases and medical conditions.

What is an MRI Scan?

What Does an MRI Scanner Look Like & How Does it Work?

The MRI scanner looks like a tube which is surrounded by a giant circular magnet. A moveable bed is present on which the patient is made to lie down and this table then passes into the magnet. A strong magnetic field is produced by the magnet that brings the protons of hydrogen atoms into alignment. All this then gets exposed to a beam of radio waves which results in spinning of different protons of the body. This produces a faint signal which is picked up by the receiver part of the MRI scanner. A computer processes this receiver information which then leads to generation of an image. The resolution of the image which is produced by MRI is very intricate and detailed and can detect even minute changes of the structures inside the body. Contrast agents are used in some MRI scan procedures to increase the accuracy of the images.

What is the Purpose of the MRI Scan & When is it Used?

MRI scan is one of the most accurate methods of detecting disease in the body. MRI scan is the most commonly used imaging test after other testing methods have failed to provide sufficient information for confirmation of a patient’s diagnosis.

MRI scan of the Head: Trauma/injury to the brain needs and MRI scan where it will help detect any swelling or bleeding. Other abnormalities which can be detected with an MRI scan of the head include brain tumors, brain aneurysms, stroke and inflammation or tumors of the spine.

MRI scan in Neurology: MRI scan is used by neurosurgeons in defining brain anatomy and also in assessing the integrity of the spinal cord after any injury. MRI scan is also used to detect or diagnose any problems related to vertebrae and the intervertebral discs of the spine.

MRI scan in Cardiology: MRI scan is also used for evaluation of the structure of the aorta and heart, as it helps in detection of ay tears or aneurysms. MRI scans however, are not the first line of imaging test in case of trauma/injury.

MRI scan in other systems of the body: MRI scan provides valuable information regarding organs and glands present inside the abdomen. MRI scan gives accurate information about the structure of the soft tissues, joints and bones of the body. The results of the MRI scan give valuable input regarding whether surgery can be performed or not.

What are the Risks, Side Effects & Benefits of an MRI Scan?

An MRI scan is a radiology imaging test which is not only painless, but also avoids exposure to x-ray radiation. As of now, there are no known or reported side effects or dangers from MRI scan. MRI scan is not painful and since exposure to radiation is not involved, this procedure can be done without any problems. However, there is a small theoretical risk to the fetus in the first trimester. For this reason, MRI scan should be avoided on pregnant women.

As the patients have to lie within a huge cylindrical structure, there is a chance that the patient can get claustrophobic during the procedure. Such patients who are at risk for feeling claustrophobic should talk to their doctor beforehand so that they can be given a mild sedative to help them relax. The MRI machine also tends to make a clanking noise when it is working, so this can be unpleasant to some patients.

MRI scan has many benefits, as it gives precise and accurate information in detecting any structural abnormalities present in the body.

What Should be Done Before the MRI Scan?

Patient should not wear anything and if there is any metallic jewelry or devices which the patient is wearing, then the technician or the doctor should be notified before the MRI scan is done. This is because presence of any metallic materials, foreign material or surgical clips, metallic bone plates, artificial joints or any prosthetic devices will significantly distort the images which are generated by the MRI scanner. Patients having metal implants, heart pacemakers or metal chips cannot be scanned using an MRI as there is risk that the magnet present in the MRI scanner will displace the metal present within the body. Likewise patients with metallic ear implants, artificial heart valves, chemotherapy pumps, bullet fragments, and insulin pumps cannot undergo MRI scanning.

What Happens During an MRI Scan?

During the MRI scan, the patient has to lie in a closed area within a magnetic tube. As patients have to lie within an enclosed space, they may feel claustrophobic during the MRI scan procedure. Therefore, patients who have a previous history of claustrophobia should inform their doctors and the radiology staff regarding this. Patient may be given a mild sedative before the MRI scan to relax and to alleviate the claustrophobia. The MRI staff will be present near the patient during the MRI scan. Other than this, the patient will be able to communicate with the doctor and the staff with the use of a buzzer (or something like that) so that patient can notify the concerned people if he/she is unable to withstand the MRI scan.

What is the Difference between an MRI scan and a CT scan?

  • There are no x-rays or ionizing radiation as such involved during an MRI scan.
  • MRI scans are also more intricate, accurate and detailed than CT scans.
  • MRI scans can illustrate all the soft tissues and also higher density tissues like bone more clearly than CT scan.
  • MRI scan gives more clear, accurate and more anatomically detailed images than CT scan.
  • The difference between an abnormal tissue and normal tissue can be seen more clearly on an MRI as the anatomical differences between these types of tissues are more accurately visible on MRI scan.
  • MRI scan also makes it possible to differentiate between cystic lesions and malignant tumors, to identify the areas of inflammation and infection for assessment of tendon joint tears.
  • With MRI scan, different images from different planes can be produced without the patient having to move.
  • However, all this also makes MRI scans more costly than CT scans.
  • MRI scans also take longer to complete than a CT scan. The duration of an MRI scan depends on the part of the body which needs to be imaged.
  • All these reasons make MRI scan more preferable than a CT scan for imaging different organs and structures of the body such as the brain, joints and the spinal cord.

How Does a Patient Prepare for an MRI Scan & How is it Performed?

Before the MRI scan is done, all metallic objects from the patient’s body are removed. Sometimes, if the patient is anxious or feels claustrophobic, then a mild sedative is given to help the patient relax during the MRI scan. During the MRI scanning, the patient needs to lie still otherwise the accuracy of the images produced will be affected. Patient has to lie still within a closed environment within the MRI machine. It is important that the patient breathe normally and stay relaxed during the procedure. Patient can interact with the MRI technologist throughout the test. During the MRI scanning, loud and repetitive clicking noises can be heard as the scanning proceeds which is no cause for alarm for the patient. In some cases, patient is given intravenous contrast to help enhance the images from MRI scan.

What is the Duration of MRI Scan Procedure?

The duration of the MRI scanning depends on the area of the body which needs to be scanned or studied, however, the time taken for an MRI scan can range anywhere between 30 minutes to 1 and 1.5 hours.

When & How are the Results of the MRI Scan Available?

After the completion of the MRI scan, the computer produces visual images of the part of the body which was scanned. These images are then transferred to a film (hard copy). These films are interpreted by a radiologist who is a physician specially trained to interpret images of the body. The final interpretation from the radiologist is then transmitted to a report to the doctor who had requested the MRI scan for the patient. The doctor then discusses the results with the patient and family members of the patient.

What does the Future of MRI scan look like?

Newer MRI scanners are being developed by scientists, which are more small and portable devices. These new MRI scanners are supposedly very useful in detecting tumors and infections of the soft tissues of the hands, elbows, feet and knees. Testing is still under process regarding the application of these new MRI scanners to medical practice.

Also Read:

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:January 23, 2018

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