Positron emission tomography (PET) is a nuclear medicine imaging technique that produces 3D images of functional processes in the body. It works by detecting pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (radiotracer) introduced into the body on a biologically active molecule. A PET scan can provide metabolic information about normal and abnormal tissues that can help detect and diagnose disease. Common clinical uses include evaluating cancer, heart disease, brain disorders, and more. Limitations include cost and the need for on-site facilities to produce short-lived radiotracers.

1. POSITRON EMISSION TOMOGRAPHY
BY
SWAPNA SUCHISMITA
REGD. NO - 200705180046
SUPERVISED BY
Mr. BIBHUDUTTA MISHRA
DEPARTMENT OF ZOOLOGY (SoAS)

2. CONTENTS
1. INTRODUCTION
2. PET COMPONENTS
3. HOW PET WORKS?
4. PET IMAGE FORMATION
5. APPLICATIONS
6. LIMITATIONS
7. REFERENCES
8. ACKNOWLEDGEMENTS

3. INTRODUCTION
• Positron emission tomography (PET) is a functional imaging technique that uses
radioactive substances known as radiotracers to visualize and measure changes in
metabolic processes, and in other physiological activities including blood flow, regional
chemical composition and absorption.
• PET is a type of nuclear medicine procedure
that measures metabolic activity of the cells of
body tissues.
• It is actually a combination of nuclear medicine
and biochemical analysis. Used mostly in patients
with brain or heart conditions and cancer.

4. PET COMPONENTS
• PET comprises:-
A scanner gantry
i. Detector
ii. Septa
iii. Coincidence circuit
Table
Computer
Cyclotron

5. How does PET works?
• PET works by using a scanning device (a machine with a large hole at its center) to
detect photons (subatomic particles) emitted by a radionuclide in the organ or tissue
being examined.
• The radionuclides used in PET scans are made by attaching a radioactive atom to
chemical substances that are used naturally by the particular organ or tissue during its
metabolic process.
• For example, in PET scans of the brain, a radioactive atom is applied to glucose (blood
sugar) to create a radionuclide called fluorodeoxyglucose (FDG), because the brain uses
glucose for its metabolism. FDG is widely used in PET scanning.
• The radionuclide is administered into a vein through an intravenous (IV) line.
• The PET scanner slowly moves over the part of the body being examined. Positrons are
emitted by the breakdown of the radionuclide.
• Gamma rays called annihilation photons are created when positrons collide with
electrons near the decay event. The scanner then detects the annihilation photons, which
arrive at the detectors in coincidence at 180 degrees apart from one another.

6. • A computer analyzes those gamma rays and uses the information to create an image
map of the organ or tissue being studied.
• The amount of the radionuclide collected in the tissue affects how brightly the tissue
appears on the image, and indicates the level of organ or tissue function.
• For example, the healthy tissues uses glucose for energy, it accumulates some of the
glucose to show up on the PET images. The cancerous tissues uses more glucose than
the normal tissues. So, it will accumulate more of the glucose and will appear more
brighter than the normal tissues on the PET images.

7. PET IMAGE FORMATION
• Each pair of parallel and opposite detectors produces a coincidence line, which is
unique in terms of location and direction.
• A large number of such coincidence lines form the data set and by the use of which a
cross-sectional image can be reconstructed. Each coincidence event represents a line in
space connecting the two detectors along which the positron emission occurred (the line
of response, LOR)
• This set of data in terms of two-dimensional matrix is called ‘Sinogram’ and provides a
set of projection data for reconstruction of image.
• Sinogram data is then used to reconstruct the image using filtered back projection or an
interactive technique.

8. APPLICATIONS
 Oncology
• Role in lesion detection, lesion characterization, staging of malignant lesions and
assessment of the therapeutic response.
Brain
• PET Study the brain's blood flow and metabolic activity. It aid in discovery of nervous
system problems, such as Alzheimer's disease, Parkinson's disease etc.
Heart
• PET can help find damaged heart tissue especially after a heart attack and can help
choose the best treatment such as coronary bypass heart surgery for a person with
heart disease.

9. LIMITATIONS
• The high costs of cyclotrons needed to produce the short-lived radionuclides for PET
scanning and the need for specially adapted on-site chemical synthesis apparatus to
produce the radiopharmaceuticals after radioisotope preparation.

10. REFERENCES
• Cherry SR: Fundamentals of positron emission tomography. Journal of Clinical
Pharmacology. 2001;41:482-491.
• A. K. Shukla and Utham Kumar : Positron emission tomography: An overview, Journal
of medical physics, 2006 Jan 31(1): 13–21.

11. ACKNOWLEDGEMENTS
• My subject teacher Mr. Bibhudutta Mishra.
• Dr. Yashaswi Nayak, HoD and Dean (SoAS).
• All the faculty members of department of zoology, SoAS, CUTM.
• Family and friends.