The brain imaging methods

(This image is taken from the site: https://commons.wikimedia.org/wiki/File:Estacion_de_trabajo_PET_TAC_keosys.JPG).

The advent of new techniques for the visualization of the brain has opened up new scenarios. The oldest technique is tomography computed (TC). TC scan uses an X-ray beam and detectors positioned on the opposite sides of patient's head. It allows to distinguish gray matter (cell bodies) from white (axons). TC also allows to recognize the ventricles and other brain structures (Parves, Augustine, Fitzpatrick, Hall, LaMantia, White, Neuroscience, Sinauer Associates Inc).

Another common technique is magnetic resonance imaging (MRI). It dates back to the '80s. MRI uses magnetic field and radiofrequency pulses. These pulses affect the rotation of the atoms. These atoms begin emitting oscillatory energy. Through the use of this technique, the operators are able to build detailed images of the brain. MRI is now the preferred method for visualization of brain structure. In fact, it is harmless and non-invasive. A variant of magnetic resonance imaging is the visualization with diffusion tensor imaging (DTI). This technique allows you to view the connections formed by the axons and the cerebral vasculature.

Other techniques, however, enable us to view functional changes in the brain. They exploit the changes in metabolism and blood flow of patients. These techniques include positron emission tomography (PET), single photon emission computerized tomography (SPECT) and functional by magnetic resonance imaging (fMRI).

In PET the operators inject isotopes into the patient bloodstream. These isotopes accumulate in the more metabolically active areas. Detectors placed around patient's head make the disclosures.

SPECT is similar to PET. It uses compounds labeled with radioisotopes which emit photons.

FMRI is instead based on the following phenomenon. When a brain area faces a task, it uses oxygen. This causes a change of the magnetic resonance signal. The devices detect this change. FMRI images have a better resolution than the other techniques.

Finally, there is magnetoencephalography (MEG). This methodology has a better temporal resolution than the other methods. Iy keeps track of the magnetic fields generated by the brain. However, the MEG does not provide structural data. For this reason, scientists associate MEG with magnetic resonance, creating a visualization technique called magnetic source image (MSI; Parves, Augustine, Fitzpatrick, Hall, LaMantia, White, Neuroscience, Sinauer Associates Inc).