Magnetic resonance imaging (MRI) - what it is?

Magnetic resonance imaging that is called "MRI," is a diagnostic test that allows you to view the inside of our body without performing surgical operations or administering dangerous ionizing radiation. It was developed around 1980; magnetic resonance imaging has undergone a constant process of technological evolution over the years. Today, due to its extreme diagnostic precision and the almost total absence of side effects, it has gained a role of primary importance in the diagnosis of numerous diseases. Particularly useful in obtaining detailed images of the brain and spine, it can also provide excellent information in the traumatology, oncological, orthopedic, cardiology, and gastroenterological fields. The only limit to its diffusion remains the high cost of the equipment and maintenance operations.

How does Magnetic resonance imaging (MRI) work?

The principle of operation of magnetic resonance imaging is extremely complex and fully comprehensible only to those who know the physical theories underlying quantum mechanics.

By simplifying the concept as much as possible, we can compare atomic nuclei to many small magnets. A bit like a compass needle, in the presence of an external magnetic field, these tiny particles tend to arrange themselves in a preferential direction. If radio waves are emitted at this point, the nuclei undergo temporary position changes. During this transitory phase, the atoms emit signals that can be captured by an electronic detector, which transmits them to a powerful computer where they will be analyzed and processed.

For this reason, magnetic resonance imaging uses a powerful magnet and a radio wave generator with a frequency of 42 megahertz, which corresponds to the number of turns that the protons of the hydrogen atom perform on themselves in one second. This element was chosen both for its physical properties and for its abundance within the human organism. Since not all atomic nuclei take the same time to return to the initial position, analyzing this period, it is possible to recreate a three-dimensional map of the internal anatomical structures, also highlighting their state of hydration.

Risk factors and side effects

Magnetic resonance imaging is a safe and completely harmless investigation for the human organism. The absence of ionizing radiation makes it particularly suitable for the repetition of tests within a short time.

Due to the magnetic field generated by the equipment, people with internal metal appliances, such as pacemakers, metal implants (teeth, eyes, bones, etc.) and vascular clips, cannot undergo the examination. Due to advances in technology for several years now, most of the metals used for medical use are compatible with magnetic resonance imaging.

Application fields

Magnetic resonance imaging (MRI) is successfully used to obtain detailed images of many tissues. The quality of the results allows you to appreciate details that cannot be detected with other diagnostic techniques. Just to cite a few examples, it is possible to study the vascularization of the tissues, the state of hydration of the intervertebral discs, evaluate the health of the joints, and diagnose with extreme precision neurological diseases and some tumor forms.

Magnetic resonance is used to diagnose a wide variety of pathologies, the technique allows, in fact, visualizing the skeleton, joints, and internal organs. The quality of the results allows evaluating details that cannot be detected with another diagnostic technique. For example, with the rm examination, it is possible to investigate the state of hydration of the intervertebral discs, study the vascularization of the tissues, evaluate the health of the joints and diagnose, with remarkable precision, neurological diseases and some tumor forms.

Most used types

Magnetic resonance imaging is used in many fields, in the neurosurgical, neurological, oncological, traumatology, cardiology, orthopedic, gastroenterological fields. The most used types of magnetic resonance imaging are:

- MRI of each joint of the upper limb (shoulder, elbow, wrist, and hand) and lower limb (hip, knee, ankle, and foot)

- Magnetic resonance imaging of the temporomandibular joints,

- Magnetic resonance imaging of the brain,

- Intracranial vascular magnetic resonance imaging, always without contrast medium (angio-MRI brain)

- Vascular magnetic resonance imaging of extracranial arteries, always with contrast medium (angio-RM)

- Magnetic resonance imaging of the chest,

- MRI of the pelvis,

- Magnetic resonance imaging of each skeletal segment.

- MRI cardiac.

- Magnetic resonance imaging of the abdomen (upper, lower, or full).

- Magnetic resonance imaging of the cervical, dorsal, lumbosacral spine.

- Massive facial MRI.

- Magnetic resonance imaging of the breast.

- Magnetic resonance imaging of the neck.

- Magnetic resonance with cholangiographic technique (cholangitis-MRI).

- Magnetic resonance with urographic technique (Uro-RM).

- Multiparametric magnetic resonance imaging of the prostate.

Exam preparation

Magnetic resonance imaging generally does not require fasting or observance of particular diets, so the patient is completely free to eat according to his preferences. Before the examination, the subject is invited to take off any object or clothes containing metal parts (bags, jewelry, belts, wallet, shoes, etc.). A questionnaire will be filled in together with the doctor or staff to ensure that there are no contraindications to the examination.

Execution

After removing any object or garment containing metal, the patient is made to lie down on a bed, which through electronic control, will scroll until it is positioned between the poles of the magnet. In traditional machinery, the shape of the equipment itself could create problems for those suffering from claustrophobia. Today, however, even more modern, open-structure machines are available, where the problem does not arise.

During the examination, no form of collaboration is required from the patient, other than to relax and warn the staff through special tools in case of illness. The devices are, in fact, equipped with speakers and microphones to communicate with the doctor or staff. Special earphones are also provided to protect the rather loud and dry noises due to the emission of radio waves.

The average duration of the exam is generally between twenty and thirty minutes, even if the most modern techniques allow reducing the detection times. To improve image quality and make the diagnosis safer, the doctor may decide to inject gadolinium, a contrast agent generally free of side effects. 

Author: Vicki Lezama