PET SCAN [ back to Glossary Index ]
PET Scan or positron emission tomography is a non-inasive neuro-imaging technique which works on the premise that healthy brain cells will metabolize much more glucose during mental tasks than damaged, dying or dead brain cells. The brain is a highest user of glucose and oxygen  than any other organ in the body. The patient undergoing a PET scan receives an IV drip of glucose tagged with a radio-isotope tracer, performs specified mental tasks for about 20 minutes and then places his head inside a "gamma camera." When the positrons (positively charged subatomic particles) in the glucose are "taken up" into activated brain cells and come into contact with negatively charged electrons, they neutralize each other and send gamma rays off in exactly opposite directions. The gamma rays emitted from the brain are picked up by the camera and fed instantly into a powerful computer which will reconstruct the spatio-temporal pattern in a 3 dimensional, color coded map depicting how the brain is functioning. Different shades of color correlate with differing levels of brain activity in different regions of the brain, and are used to visually highlight even the most subtle disturbances in the expected levels of brain metabolism for a given person (according to comparisons with controls matched for age, gender, etc). An example of a PET scan may be found on the Welcome Page of this website. To increase accuracy the patient is weaned off any drugs he was taking for medical conditions during the week preceding the test, because those drugs may change and complicate the picture of how the unmedicated brain is performing it's job.

PET scans cost in the area of $2,500 to $3,000. They were originally used to diagnose metastatic cancer and heart disease, but have been used with great frequency to study disturbances of normal  brain function in the past two decades in both the the research and clinical settings, including the diagnosis of persons with schizophrenia and mood disorders as well as the planning of rehabilitation for persons with a TBI. While

insurance company "experts" assert in TBI litigation that PET scans are still a purely experimental research technique unproven in clinical medicine, this is false. Health insurance companies across the United States pay for them to be done on a regular basis in the diagnosis and rehabilitation of persons with brain injuries from cancer, stroke and trauma too. Experts in the interpretation of PET scans have charted different "activation patterns" of the brains of persons with a variety of neurologic and psychiatric disturbances, and have acquired a huge data base which can be used for comparison purposes.