Brain Magnetic Resonance Imaging (MRI)

A brain MRI enables detailed visualization of the internal structures of the head, including the brain. It is a non-invasive test that does not produce side effects.

Resonancia magnética de cráneo

General Description

Brain MRI is a diagnostic imaging technique used to obtain detailed images of the brain and its surrounding structures. It employs a device that generates a high-powered magnetic field and emits radio waves. This is a non-invasive technique free of health risks, as it does not use ionizing radiation.

Two types of brain MRI can be performed:

Closed MRI: The patient is inserted into a tube approximately 70 centimeters in diameter. This device produces a very strong magnetic field, resulting in high-quality images. It is the preferred option.
Open MRI: Conducted with a machine consisting of two plates facing each other, separated by approximately 180 centimeters. Because it is not enclosed, the magnetic field is less powerful. This option is selected for patients with obesity or claustrophobia.

This technique provides information about both the anatomy and function of organs, making it very useful for diagnosing a wide range of diseases. Additionally, brain MRI is used to plan surgeries, assess treatment effectiveness, and monitor disease progression.

When is it indicated?

Brain MRI not only studies the brain but also evaluates other tissues within the head. It helps detect or monitor various conditions, including:

Malignant tumors
Aneurysms: arterial bulging
Hemorrhages: blood vessel obstruction due to clots
Ischemias: interruption of blood flow in tissue
StrokeStroke Stroke or cerebrovascular accident
Brain injuries
Multiple sclerosis
Alzheimer’s disease
Dementia
Parkinson’s disease
Epilepsy
Malformations
Infections
Cerebral palsy
Nerve disorders causing hearing or vision loss, or balance problems
Trauma-related lesions

This test is contraindicated in patients with metallic implants such as pacemakers, prostheses, or cochlear implants.

How is it performed?

Brain MRI images are acquired using a device composed mainly of three parts:

Gradient coils: generate time-varying magnetic fields
Radiofrequency coils: emit pulses of electromagnetic waves
Computer system: collects data and converts it into images

The MRI works on the principle that protons in body tissues align within the magnetic field. Radiofrequency pulses cause these protons to spin and resist alignment. When the pulses stop, protons realign, releasing energy that varies in intensity depending on chemical composition. This information is processed into images displayed in different shades of gray according to the energy intensity.

Besides standard MRI, a contrast-enhanced MRI using gadolinium can be performed. Certain cells—especially those in blood vessels and cancerous tumors—absorb this contrast agent more readily, appearing brighter on images and facilitating identification.

Risks

Brain MRI is generally safe, although patients with claustrophobia may experience anxiety when entering a narrow tube. In such cases, sedation or an open MRI may be considered.

Rarely, allergic reactions to the contrast agent may occur, presenting as itching, headache, or nausea.

What to expect from a brain MRI

The patient changes into a hospital gown and removes all metal objects, including jewelry, hearing aids, and dentures. Some cosmetics contain metal particles and may need to be removed.

Lying supine on the examination table, the patient is given earplugs to reduce the loud knocking noises generated by the machine during the magnetic field activation. These sounds are normal despite ear protection.

If contrast is administered, a slight prick is felt during intravenous injection. Sometimes, a brief sensation of heat or cold is experienced as the contrast circulates through the bloodstream.

The patient must remain as still as possible during the procedure, which lasts between 30 and 60 minutes, to avoid blurry images. After completion, normal activities can be resumed immediately.

Medical specialties requesting brain MRI

Brain MRI is performed by radiology specialists and is commonly requested by departments such as oncology, neurology, ophthalmology, otolaryngology, pediatric neurology, and neurosurgery.