Magnetic Resonance Imaging


  1. What is magnetic resonance imaging?
  2. What does it consist of?
  3. Why is it performed?
  4. Preparing for the test
  5. What does the patient feel during the exam?
  6. Risks
  7. Abnormal results

What is MRI?

MRI is a diagnostic test. It is an imaging test that uses powerful magnets and radio waves to create images of a person’s body. No radiation, i.e., x-rays, is used.

MRI provides medical imaging that uses a magnetic field and computer-generated radio waves to create detailed images of both the organs and tissues of the body.

Typically, MRI machines are large magnets and are shaped like a tube. When the patient lies down inside the MRI machine, the magnetic field causes a temporary realignment of the body’s water molecules. In this way, the waves cause the aligned atoms to generate weak signals that are used to create cross-sectional MRI images.

In recent years, the MRI apparatus has also made it possible to produce 3D images so that they can be viewed from different angles.

What does it consist of?

Signals emitted by electromagnetic waves are collected and translated into images that can be observed on a monitor, allowing the practitioner to study them.

The MRI apparatus is tubular in shape and is open at both ends. To perform the test, the patient must lie down on a movable table that will slide towards the inside of the tube. The device creates a strong magnetic field around the patient, emitting radio waves into the body. However, the patient will not feel pain at any time during the test.

In any case, the MRI may last between 15 and 60 minutes, and the patient must remain completely still, otherwise the images may be blurred.

Why is it performed?

MRI allows experts to perfectly differentiate the different anatomical structures in order to make a clearer and more complete diagnosis. Thanks to this ability to observe tissues and organs in detail, the specialist can diagnose the presence of lesions or diseases in the area studied.

There are several reasons why a person may undergo an MRI:

  • MRI of the head and spinal cord: multiple sclerosis, aneurysms, eye disorders, ear disorders, stroke, tumors, head injuries…
  • Breast MRI: breast and breast cancer, heart function, blood blockages…
  • MRI of internal organs: spleen, kidneys, liver, prostate, ovaries, spleen…
  • MRI of bones and joints: bone infections, soft tissue tumors, ligamentous lesions, spinal abnormalities, trauma.
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Preparation for MRI

The patient, before undergoing the test, can eat normally and continue taking the usual drugs. In some cases, depending on the area of the body to be examined, it is necessary for the patient not to eat or drink for a period of four to six hours before the examination, but in this case the physician will indicate this.

Generally, the patient should put on a hospital gown and remove all objects that may affect the MRI images, such as the following:

  • Metal objects
  • Watches
  • Hairpins
  • Hearing aids
  • Dentures
  • Underwire bra
  • Cosmetics that have metal particles in their composition

What does the test feel like?

This test usually lasts between 30 and 60 minutes. It is painless, but if the person is afraid of enclosed spaces it can cause claustrophobia. In this case, the patient may be given medication to numb him/her and make him/her feel less anxious.

In any case, it is important that the patient remains still during the exam.

Risks of MRI

MRI does not use any radiation. The type of contrast usually used is gadolinium, which is very safe and rarely causes any type of allergic reaction.

However, the strong magnetic fields created during the test may cause some implants, such as pacemakers, to not work as well. The magnets may also cause a piece of metal inside the body to shift or change position.

What abnormal results mean

The radiologist, who is the expert in charge of interpreting the MRI images, will analyze the images and inform the physician of the results.

The result will always depend on the pathology and the organ studied. Sometimes benign or malignant tumors, infections, inflammations, bone pathologies, fractures, malformations, ligament or meniscus affectations, thrombi, infarcts and hemorrhages can be found. When an affectation appears in the MRI, the patient should be referred to the specialist doctor in charge of the treatment of the pathology in question.