Aging Begins at 30

Watching Cells Work Inside the Body

Our son had a CAT scan of his brain which he found slightly claustrophobic but what "blew his mind" was to see his brain "laid out like slices of bologna in the deli."

CAT scans (computer assisted tomography) creates cross-sectional (from the Greek tomos - a knife) of our brain and other organs by x-rays. A new PET scan (Positron Emission Tomography) cuts similar slices of the brain using gamma rays. It also shows which tissues are living and using energy. PET combines medicine, chemistry, physics, and physiology to study the function of the brain, heart, and tissues throughout the body.

PET can be used to find tumors and find out how well they respond to treatment or to find a recurrence and differentiate them from benign tumors. It can differentiate live heart muscle from dead so that expensive and potentially risky bypass of blood can be directed to the right part of the heart. PET scan can also show live or dead brain tissue after a stroke and where in the brain seizures may be occurring. It can also show why the brain of a schizophrenic patient works differently. It can even show the brain in action when seeing pictures or thinking thoughts.

A typical PET scan begins by IV injection of a small safe dose of radioactive "tracer" bound to sugar or water. The patient reclines comfortably in a bed for an hour or so inside the PET camera. The radioactive sugar goes to areas of the body where energy is being used. Electrons from the tissue combine with positrons from the radioactive tracer to produce gamma rays (similar to x-rays). These rays are recorded by the camera and reconstructed into 3-D pictures by the computer. The radioactive materials that are used in the PET scan only last minutes to hours so a nuclear particle accelerator cyclotron is needed to make them. A cyclotron accelerates protons to a very high energy and collides them into a stable gas or liquid which is made temporarily radioactive and synthesized into a radioactive trace like sugar.

PET scans are very expensive but they can decrease medical costs by avoiding unnecessary surgery or showing where surgery can do the most good.

The PET scan is non invasive, only an IV or urinary catheter or both are used. The radioactive tracers have such a short life that there is very little radiation exposure to the patient and, as the tracers are similar to normal substances, no side effects.

Significant progress has been made in recent years. We have gone from still snapshots of the brain and heart to moving pictures of these organs in action. Now we can peer inside the skull and "see" people thinking. As one journalist put it, "Know the brain is all its electrical magnetic and chemical glory."

Section Top | Title Page

See related Patient Topics Diagnostic Imaging or Procedures and Therapies.

See related Provider Topics Diagnostic Imaging or Procedures and Therapies.

All contents copyright © 1992-2004 the Author(s) and The University of Iowa. All rights reserved.

http://www.vh.org/adult/patient/internalmedicine/aba30/1996/petscan.html