The Brain: Understanding Neurobiology
Sponsoring Institutes
skip navigation Main Getting Started Teacher's Guide Student Activities About NIH and NIDA
glossary | map | contact 
National Institutes of Health website National Institute on Drug Abuse website

 

National Institutes of Health
National Institute on Drug Abuse website

The Brain: Understanding Neurobiology

Main    Getting Started    Teacher's Guide    Student Activities    About NIH and NIDA

Glossary    Map    Contact

skip navigation linksLesson 1—The Brain: What's Going on in There? student in a classroom

Lesson 1—The Brain: What's Going On in There?

Analyzing Brain Images How is PET done? What Does this Part of the Brain Do? Looking at the Human Brain

Transcript for How Is PET Done? Video

PET stands for positron emission tomography. It involves an isotope that is injected and emits some radiation, a ring of detectors which detects this radiation, and the conversion of this detected radiation into an image. The PET scanner consists of the bed, which is not the most comfortable bed. And this bed is slowly moved through a ring of detectors. Basically, it looks very similar to a CAT scan. The CAT scan would send radiation from outside through the body while we inject isotopes that send radiation from inside the body outside to the detectors.

I tell the patients that they have to be aware of two things. One, the bed is quite uncomfortable, and two, it’s kind of boring to be in the scanner. At the time of the radioisotope injection, the patient might feel a little bit of a metallic taste in his mouth. Then there is an uptake period. We wait until the radioisotope really accumulates in the tissue that we want to look at. And after these 40 minutes, the patient is moved into the scanner, during which time the images are being taken.

When the patient is in the scanner, you accumulate data over, let’s say, a five- or six-minute period and convert it into a gray scale. The impulses are digitized. Usually when you see color displays, normally, it’s indicated in red or yellow. So if you have a 16-grade color scale, each of the colors would represent a six percent change in radioisotope activity. The scanner actually acquires 63 image planes at the same time in this given field of view, which is about 15 centimeters. You can, in fact, label any compound that you have in mind with a positron emitter and image the process that you’re interested in imaging.

back to Student Activities