Positron emission tomography (PET) is an imaging technique that uses radiolabeled tracers to produce images showing their distribution in the body. During a PET scan, a tracer containing a radioactive isotope is injected and decays, emitting positrons. The positrons interact with electrons, producing pairs of gamma rays detected by the PET scanner to reconstruct images. PET scans are used to study brain function, detect and characterize cancers, and examine heart disease. Advantages include showing tissue function, but disadvantages include expense and limited availability.

1. S.K.CHAUDHARY EDUCATIONAL TRUST’S
SHANKARA INSTITUTE OF TECHNOLOGY
KUKAS, JAIPUR
PRESENTED BY:
ROHIT KUMAR
B.TECH. 4TH
YEAR
12ESIEC048
SESSION (2015-2016)
POSITRON EMISSION TOMOGRAPHY
PRESENTED TO:
MR. RAJESH KANWADIA
(ASSISTANT PROF.)
MS. SHWETA AGARWAL
(ASSISTANT PROF.)
E.C.E. DEPARTMENT
1

2. P.E.T.
Positron Emission Tomography
Presented by Ahmad Bdier

4. Presentation Outline
 What is PET?
 The Basic PET Process
 Basic Principle of PET
1) Positron Emission
2) Emission Detection
 A positron emission tomography (PET) scan is
done to
 Clinical Applications of PET
 Advantages and Disadvantages of PET

5. What is PET?
 PET stands for Positron Emission
Tomography and is an imaging technique
which uses small amounts of radiolabeled
biologically active compounds (tracers) to
help in the diagnosis of disease. The
tracers are introduced into the body, by
either injection or inhalation of a gas, and
a PET scanner is used to produce an image
showing the distribution of the tracer in
the body.

7. The Basic PET Process

8. Basic Principle of PET (Positron
Emission)
 Positron Emission occurs when the Proton
rich isotope (Unstable Parent Nucleus)
decays and a Proton decays to a Neutron,
a Positron and a Neutrino. After traveling a
short distance (3-5mm), the positron
emitted encounters an electron from the
surrounding environment. The two
particles combine and "annihilate" each
other, resulting in the emission of two
gamma rays in opposite directions of
0.511 MeV each.

9. Positron Emission (continued)

10. Positron Emission

11. Positron Emission
 Electrons and a positron traveling after being
emitted from the nucleus of the radioactive
element.

12. Positron Emission
 The positron combines with electron forming
positronium as an intermediate.

13. Positron Emission
 Annihilation of and electron and a positron
resulting in the emission of two opposite gamma
rays.

14. Positron Emission
 The image acquisition is based on the external
detection the emitted Gamma-rays, and a valid
annihilation event requires a coincidence within
12 nanoseconds between two detectors on
opposite sides of the scanner. For accepted
coincidences, lines of response connecting the
coincidence detectors are drawn through the
object and used in the image reconstruction. Any
scanner requires that the radioisotope, in the field
of view, does not redistribute during the scan.

15. Types of Coincidences in PET

16. Basic Principle of PET (Emission
Detection)
 As positron annihilation occurs, the tomograph
detects the isotope's location and concentration.

17. Emission Detection
 Shown here in schematic form, the light photons are
converted to electrical signals that are registered by the
tomograph's electronics setup almost instantly.

18. Emission Detection
 The ring of squares represents one ring of detectors in a
PET scanner, which may, for example, have fifteen such
rings for simultaneous tomography of many transaxial
slices

19. Emission Detection
 The tomograph's reconstruction software then takes the
coincidence events measured at all angular and linear
positions to reconstruct an image that depicts the
localization and concentration of the radioisotope within a
plane of the organ that was scanned.

20. A positron emission tomography
(PET) scan is done to
 Study the brain's blood flow and metabolic activity. A
PET scan can help a doctor find nervous system
problems, such as Alzheimer's disease, Parkinson's
disease, multiple sclerosis, transient ischemic attack
(TIA), amyotrophic lateral sclerosis (ALS),
Huntington's disease, stroke, and schizophrenia.
 Find changes in the brain that may cause epilepsy.
 Find some cancers, especially cancers of the breast,
brain, lung, colon, or mouth. In its early stages
cancer may show up more clearly on a PET scan than
on a CT scan or an MRI.
 See how advanced a cancer is and whether it has
spread to another area of the body (metastasized). It
is often necessary to do both CT and PET scans to
evaluate cancer.

21. A positron emission tomography
(PET) scan is done to
 Help a doctor choose the best treatment for cancer.
PET scans may also be done to see whether surgery
can be done to remove a tumor.
 Find poor blood flow to the heart, which may mean
coronary artery disease.
 Find damaged heart tissue, especially after a heart
attack.
 Help choose the best treatment, such as coronary
artery bypass graft surgery, for a person with heart
disease.

23. Advantages and Disadvantages of PET
 Advantages:
 PET imaging is unique in that it shows the
chemical functioning of organs and tissues in
vivo, while other imaging techniques – such as
X-ray, CT and MRI – show structure.
 increased sensitivity and accurate attenuation
correction provided by the PET imaging
modality.

24.  Disadvantages:
• Allergic reactions to radiopharmaceuticals may
occur but are rare.
• Injection of the radiotracer may cause slight pain
and redness which should rapidly resolve.
• Expensive – due to cyclotrons needed to produce
short lived radionuclides.
• Low accecssbility.
• Takes time.

25. Conclusion
 If we look to the clinical need instead of physical
scanner parameters, then the image quality of
heavy patients and the total scanning time stand
out as a major challenge. While TOF scanners are
just entering clinical use, it will be probably
several years until they are widely available. It
can be assumed that over the next few years the
timing resolution will continue to improve.
 PET has taken a long time to move from a
research tool to routine clinical use. At the same
time, image quality has improved greatly.

26. Thank you