Positron Emission Tomography (PET)

Presenter : Khizra Samad

• PET is a nuclear medical imaging technique that produces a three-dimensional image or picture of functional processes in the body.

• The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule.

• Three-dimensional images of tracer concentration within the body are then constructed by computer analysis.

• In modern scanners, three dimensional imaging is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.

Whole-body PET scan

A Brain PET / MRI Fusion image

Why the Test is Performed ?

• A PET scan can reveal the size, shape, position, and some function of organs.• Used to check brain function• Used to diagnose cancer, heart problems, and brain disorders• To see how far cancer has spread• To show areas in which there is poor blood flow to the heart• Several PET scans may be taken over time to check how well

you are responding to treatment for cancer or another illness.

How to Prepare for the Test ?• You may be asked not to eat anything for 4 - 6 hours before the

scan. You will be able to drink water.

How the Test is Performed ?

• A PET scan uses a small amount of radioactive material (tracer). The  tracer is given through a vein (IV), most often on the inside of your elbow. 

• The tracer travels through your blood and collects in organs and tissues. This helps the radiologist see certain areas of concern more clearly.

Cont..

• You will need to wait nearby as the tracer is absorbed by your body. This takes about 1 hour.

• Then, you will lie on a narrow table that slides into a large tunnel-shaped scanner. The PET picks up detects signals from the tracer. A computer changes the signals into 3-D pictures. The images are displayed on a monitor for your doctor to read.

• You must lie still during test. Too much movement can blur images and cause errors.

• How long the test takes depends on what part of the body is being scanned.

How the Test Will Feel ?

• You may feel a sharp sting when the needle with the tracer is placed into your vein.

• A PET scan causes no pain. The table may be hard or cold, but you can request a blanket or pillow.

• An intercom in the room allows you to speak to someone at any time.

• There is no recovery time, unless you were given a medicine to relax

Risks

• The amount of radiation used in a PET scan about the same amount as for most CT scans.

• Short-lived tracers are used so the radiation is gone from your body in about 2-10 hours.

• Tell your doctor before having this test if you are pregnant or breast feeding. Infants and babies developing in the are more sensitive to radiation because their organs are still growing.

References

• http://www.nlm.nih.gov/medlineplus/ency/article/003827.htm

• http://www.nhs.uk/Conditions/PETscan/Pages/Introduction.aspx

• http://en.wikipedia.org/wiki/Positron_emission_tomography