Positron Emission Topography (PET)
Positron Emission Topography (PET) is a technique in which radioisotopes that emit positrons are injected into the person. (Positrons are similar to electrons, but they have a positive charge, whereas electron have a negative charge.) The collision of a positron and an electron in the brain results in the emission of gamma rays, which can be detected and used to note the location of brain cells of varying degrees of activity. PET scans can be used to study brain metabolism, drug distribution in the brain, and changes in blood flow due to brain activity.
The newer models of positron emission topography scanners allow for more comfortable and fast performance.
A normal pet scan which shows the difference in brain activity between reciting a set of well memorized and practiced words; anda set of words not practiced much.