fMRI, or functional magnetic resonance, is a relatively new study of brain activity. The fMRI examination allows, inter alia, accurately assess the type of cancer, quickly diagnose multiple sclerosis and Alzheimer's disease, and explain the mystery of the human mind, which is phantom pain in patients with amputated limbs. What is and how does the fMRI test work?
fMRI, i.e. functional magnetic resonance imagingis a non-invasive method of imaging the activity of the human brain during normal functioning, using the phenomenon of changing the level of blood oxygenation.
The fMRI study takes advantage of the fact that brain activity is an electrical process. Increased electrical activity of the brain, and more specifically greater activity of neurons, increases the demand for energy, i.e. for oxygen and glucose. The consequence of this process is increased blood flow through an area of the brain with increased neuronal activity. FMRI works by recording the activity of nerve cells and detecting changes in blood oxygenation and flow.
fMRI - what is functional magnetic resonance imaging?
Structural resonance is based on the magnetic properties of the atoms out of which the cells of the body are made. When atoms are placed in an external magnetic field, they are subjected to an electromagnetic pulse at radio frequency. As a consequence, physical processes are initiated thanks to which the nuclei of atoms become magnetized and become the source of the electromagnetic field themselves. The energy they emit is picked up by a computer, analyzed and converted into an image. It should be mentioned that the atoms of the cells have different magnetic properties, therefore each of them returns a signal with a different intensity. Thanks to this, it is possible to distinguish different tissues - he althy and pathologically changed ones.
In functional resonance, the source of the signal is the oxygen atoms in the blood carried by hemoglobin. Oxygenated blood (oxyhemoglobin), i.e. blood flowing through more active places in the brain, exhibits different magnetic properties than blood deprived of oxygen (deoxyhemoglobin). Hence the difference between the signal sent by active areas andinactive. In medical terminology, the dependence of the intensity of the MRI signal on the level of blood oxygenation is called BOLD (blood oxygen level dependent).
What is fMRI like?
The subject lying in the scanner performs some simple cognitive and perceptual tasks that are related to the appropriate brain function, e.g. speaking, remembering or moving the hand. If neurons work intensively in a given area, local blood flow increases there and the oxygen concentration changes. Local changes in oxygen concentration and related changes in deoxyhaemoglobin concentration are visualized in changes in the BOLD signal. This signal is read and translated into the language of a computer image. This creates an oxygenated map of the brain.
How to prepare for the test?
Before the examination, remove all items with metal elements (belts, jewelery, watches) as well as those less obvious, such as nicotine plaster.
Contraindications to the procedure
- having a pacemaker, hip implant, aneurysm clip, bone screw, or other surgical implant made of ferromagnetic materials
- claustrophobia
- back problems that prevent you from lying still for up to 90 minutes
- pregnancy
- tattoo with iron oxide pigment