MRI is a tomographic diagnosis of the body without the use of radiation. It is considered one of the safest types of examination. However, there are some limitations to its use.
What is MRI
Magnetic resonance imaging is performed using a special apparatus, inside which a constant powerful magnetic field is created. With its help, the alignment of elementary particles (hydrogen atoms) in the body of the person being diagnosed takes place. The device emits radio waves, the frequency of which coincides with the frequency of vibration of the particles, as a result of which the waves are "scanned". The computer converts the received data into an image.
Indications and contraindications for MRI of the head
Indications for an MRI of the head are persistent headaches and dizziness, loss of consciousness, fainting, numbness or sharp pain in the face, deterioration of vision and hearing. In some cases, regular tomography may be shown: the presence of hypertension, intense physical activity, engaging in highly traumatic sports (martial arts, boxing, etc.).
There are a number of categorical contraindications to MRI: pregnancy, claustrophobia (but there are open-type devices), the presence of metal implants in the body, not only because of the threat of their displacement and tissue injury, but also because of the possibility of image distortion.
The presence in the body of an artificial pacemaker (pacemaker) or hearing implant is also a contraindication, since MRI will disrupt their work. Tattoos made with a dye based on metal compounds can become a reason for replacing the method for examining the body. For metal dental implants, MRI scans should not be performed if available. Another question is whether tomography can be used if the patient has fixed metal crowns.
Earlier, for the manufacture of crowns used steel, steel with sputtering, gold with copper. MRI will not affect them, but these metals can distort the image. Modern crowns are mainly made from alloys that do not react to magnetic fields. The most common are metal-ceramic coatings, but they are not a contraindication to MRI. And yet, it is imperative to warn about the presence of any metal compounds in the body: this also applies to dental crowns.
Cases of painful sensations during MRI of the head in patients with metal crowns have not been recorded, but theoretically, the presence of several such dental coatings can significantly distort the image. The doctor decides on the safety of the procedure. In some cases, for example, the patient may be required to remove the crowns. If this is not possible, MRI can be substituted for computed tomography.