3. • Positron Emission Tomography (PET) is a nuclear imaging technique
that produces a 3-D image of functional processes in the body by
detecting the radiation emitted by photons .
• The system detects pairs of gamma rays emitted indirectly by
positron emitting radionuclide (tracer), which was previously
injected in body on a biologically active molecule,
• 3-D images of tracer concentration within the body are then
constructed by computer analysis.
• Injection of Short lived Radioactive Isotope in body.
most commonly used is FDG (fluoro-2-
• Wait till tracer gets accumulated in tissues of interests.
• Subject is placed in the imaging scanner
• Tissue concentration is recorded with time.
• As isotope decays in body, it releases a positron in body.
On interaction with an electron, it produces a pair of
8. Applications of PET
• PET is used in following areas.
• Clinical oncology (medical imaging of tumors).
• Musculo-skeletal imaging
• The greatest benefit of PET is that it can show blood and
oxygen flow and glucose metabolism to different tissues of
working brain. These measurements help in understanding
amount of brain activity and allow us to know more about
how brain works.
• PET is superior to all other imaging techniques because of its
resolution and speed of completion.
12. Brain Diseases and PET
• PET scanning is also used for diagnosis of brain diseases most
notably because all the brain diseases like tumors, strokes and
neuron damaging diseases which cause Dementia (like
Alzheimer’s disease) all cause great change in brain
metabolism which causes easily detectable changes in PET
• PET scan is most commonly used in case of certain dementias
like( Alzheimer’s Disease and Pick’s Disease) where the early
damage is not detected by using CT and MRI scans.
14. Pick’s Disease
PET scan of patient with Pick’s Disease showing Decreased Metabolism in
frontal lobe. (Activity is represented in black)
• PET is used in neuropsychology to examine links between
specific psychological processes or disorders and brain activity.
• To cure mental disorders, patients are given some drugs that
selectively bind to Neuroreceptors of interest. To check the
states of these receptors , we need to use to PET SCANS.
• Most widely used Application of PET
• Tracer used is FDG-18.
• Highly accurate as tumor cells consume lot of glucose.
• And Tracer is a glucose analog.
• Also, tracer is bound in tumor cell once it got there until it
• Thereby, giving more accurate results.
19. Musculo –Skeletal Imagaing
• One of the main advantage using PET is that it can also
provide muscle activation data about deeper lying
muscles as compared to other muscle studying
• there is an disadvantage also as provides no timing
information about muscle activation because it has to be
measured after the exercise is complete.
20. Cardiology and Pharmacology
• In Cardiology, PET helps us to detect patients at the risk of
• In pre-clinical trials, it is possible to radiolabel a new drug and
test it on animals. The drug accumulates in tissues of interest
and hence, providing information about the effectiveness of
• PET scan is very good imaging technique used in both medical
oncology and brain imaging.
• This scan is most effective due to its lesser time of completion
and better resolution and also less exposing to radioactivity
than CT scan, high accuracy in detecting brain diseases (at very
early stage too )and prediction of various strokes.
• But its high cost is a major drawback.
• In future, if we are able to reduce its cost, than this technique
can of great use to us.