Today I want to explain positron emission tomography (PET). Positron Emission Tomography (PET) is a type of scanning technique that uses a radiopharmaceutical or a radioactive chemical that we utilize in the body that will allow us to perform scans and understand the inside of the body so ultimately positron is the term we use for the production of a small subatomic particle which is produced inside the body in a particular nuclear reaction emission.

Tiny tracers

It’s all possible because of tiny tracers specially-designed radioactive molecules. The PET scanner tracks the position of the tracers inside patient revealing for example patient’s brain function in three dimensions. The tracers don’t come from a stockroom shelf. Each one has to be made fresh at a laboratory. First doctor needs to produce the radioactivity using a device called a Cyclotron. It smashes high-speed particles into ordinary atoms, transforming them into new radioactive atoms. The new atoms will give off their radioactivity. Becoming plain old regular atoms again. The molecule could be anything, a sugar a protein a hormone. Each one is tailored to a specific function in the body and will show doctors where in the body that function is happening.

Doctor’s team run special chemical reactions to create a tracer from a drug used in the brain.

The new tracer must pass quality control and checked that it will function properly.

Then the tracer is ready to use. The precious custom-made molecule is rushed to the PET clinic just the right level of radioactivity is measured out.

Then it’s injected into patient’s bloodstream. It’s not long before patient’s brain has absorbed the tracer and the clever chemistry gets to work.

After absorbing the tracer

Inside patient an incredible reaction will have been taking place. The radioactive atom on the tracer loses its radioactivity. Giving off a subatomic particle called a positron.

It’s just like the tiny negatively charged electrons found on all atoms. Except that the positron is positively charged so when the positron hits an electron at just the right speed they combine and destroy each other. The energy is released as two gamma rays that travel straight out of patient’s body in opposite directions. The PET Scanner is like a big ring of Geiger counters. When it detects two gamma rays on opposite sides of the ring, the doctors can calculate where in patient’s body the tracer must be.

By detecting thousands of these events every second and with some clever computer processing patient’s brain activity is revealed in three dimensions.

Something no other imaging technique can do.

For patient it was just a small injection. All made possible by the incredible technology of the tracer. In the next hour or so patient’s radioactivity levels will be back to normal. It’s another successful job for the incredible tracers.

The potential for PET is enormous. Different tracers can detect cancer, test heart function and even track Alzheimer’s.


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