Generality
Conceived and developed around 1980, magnetic resonance has undergone a constant process of technological evolution over the years. Today, thanks to its extreme diagnostic accuracy 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 vertebral column, it is able to provide excellent information also in the traumatological, oncological, orthopedic, cardiology and gastroenterological fields. The only limit to its spread remains the high cost of the equipment and maintenance operations.
How does it work
The principle of operation of magnetic resonance is extremely complex and fully understandable 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 little like the needle of a compass, in the presence of an external magnetic field these tiny particles tend to be placed in a preferential direction. If at this point radio waves are emitted, the nuclei undergo temporary changes in position. 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 uses a powerful magnet and a radio wave generator with a frequency of 42 megahertz, which corresponds to the number of turns that the hydrogen atom protons perform on themselves in a second. This element was chosen both for its physical properties and for its abundance in the human body. Given that 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 the state of hydration.
Application fields
MRI is successfully used to obtain detailed images of many tissues. The quality of the results makes it possible to appreciate details not detectable with other diagnostic techniques. To cite some examples, it is possible to study the vascularization of tissues, the state of hydration of intervertebral discs, assess the health of the joints and diagnose neurological diseases and some forms of cancer with extreme precision.
Risk factors and side effects
MRI is a safe and completely harmless investigation for the human body. The absence of ionizing radiation makes it particularly suitable also for the repetition of examinations at a short distance of time.
Due to the magnetic field generated by the equipment, people cannot be examined for which internal metal devices have been applied, such as pacemakers, metal prostheses (teeth, eyes, bones, etc.) and vascular clips. Thanks to advances in technology for many years now, most of the metals used for medical use are compatible with MRI.
Preparation for the exam
Magnetic resonance imaging generally does not require fasting or observance of particular diets, so the patient is completely free to feed according to his preferences.
Before the exam, the subject is invited to remove any object or garment containing metal parts (bags, jewelery, belts, wallet, shoes, etc.). A questionnaire will be filled out 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 stretched over a cot, which will be run through an electronic control to position itself 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, more modern machinery is also available, with an open structure, where the problem does not arise.
During the examination the patient does not require any form of collaboration, other than to relax and warn the staff through appropriate tools in case of discomfort. The equipment is in fact equipped with loudspeakers and microphones to communicate with the doctor or the staff in charge. Special earphones are also provided to protect 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 to reduce the detection times. To improve the quality of the images and make the diagnosis safer, the doctor may decide to inject gadolinium, a contrast agent generally free of side effects. To learn more: contrast media and magnetic resonance .
Resonance and back pain
Generally, only patients suffering from chronic and particularly disabling back pain are subjected to magnetic resonance imaging.
Considering that over 90% of cases of low back pain spontaneously regress within thirty days, undergoing this examination at an early age is practically useless.
In the image to the side, which shows the result of an MRI, it is possible to observe the presence of an herniation at the level of an intervertebral disk (red circle). Incorrectly lifting a heavy load or the continuous repetition of microtraumas can cause the crushing of this important structure and, in the most serious cases, lead to the expulsion of the substances contained therein. This leakage of material, called a herniated disc, can compress and / or inflame the adjacent nerve roots, causing sciatica (pain along the buttock, leg and foot) or cruralgia (pain radiating to the front of the thigh) .
Unfortunately, once injured, the intervertebral disc cannot regenerate and regain the lost form and functionality. However in many cases the pain tends to disappear spontaneously and in about 25-35% of the subjects does not appear even in the acute phase of the trauma. A program of physical activity, aimed at reducing body weight and correcting any postural defects, can also significantly improve the patient's condition, while preventing further injuries. SEE ALSO: the herniated disc
Body composition evaluation
This technique is also used in a medical sports context to evaluate:
- the total amount of body fat
- the thickness of the subcutaneous adipose panniculus
- the distribution of regional and total adipose tissue
- the amount of visceral or intra-abdominal adipose tissue
Despite providing valuable information, due to the low availability and high cost of the instrumentation, the use of MRI in this field is rather limited.
