PET is a nuclear medicine scan that uses radioactive tracers to visualize metabolic processes in the body. It works by administering a radioactive tracer that accumulates in tissues and organs, emitting gamma rays that are detected by a ring of scintillation detectors. This allows reconstruction of 2D images showing tracer concentration. Common tracers include carbon-11, nitrogen-13, oxygen-15 and fluorine-18, which are produced by a cyclotron. PET scans are used to detect and monitor cancer, heart disease, and brain disorders. The scans provide functional information that can be fused with anatomical CT or MRI images. While exposing patients to radiation, PET offers high sensitivity for disease detection at early stages.

1. PET
-Positron Emission Tomography

2. What Is PET?
• Nuclear medicine scan, Functional imaging
technique.
• Quantifiable – amount of radiation depends on
rate of metabolic activity
• non-invasive, but does involves exposure to
ionizing radiation,
• Usage of radioactive isotopes
(radiopharmacons) emitt β⁺ particles

3. How Does PET Work?
• Administration of radiopharmacon
• Decay of isotope internally, accumulation of
radiopharmacon in diseased tissue.
• Electron interaction  annihilation
 emission of 2 gamma photons.
• Scintillating detectors ( gamma camera).
• Collection and storage
of data  reconstruction
of 2D distribution map.
• Most scans today are combined with CT.

5. Detection Of Emission

6. Collection Of Data – Lines Of
Conicidence
Linear sampling – defining
parallel coincidence
sampling paths.
Each detector can be
operated in multiple
coincidence with many
detectors across from it.

7. Radioactive Isotopes
Common isotopes used for PET examinations and their main
properties
Isotope 11
C 13
N 15
O 18
F
Half-life (minutes) 20.3 9.98 2.05 110
Nuclear reaction 14
N (p,α) 11C 16
O(p,α) 13N 14
N(d,n) 15O 18
O (p,n) 18F
Manifactured by cyclotrons.
Cyclotron = accelerator with a circular path enforced by a magnetic field.

9. Medical Fields Of Application
• PET and PET/CT scans are performed to:
• detect cancer.
• determine spread of cancer
• Determine effectiveness of treatment, such as cancer therapy.
• Detect return of a cancer.
• determine blood flow to the heart muscle.
• determine the effects of a heart attack, or myocardial infarction, on
areas of the heart.
• Identification whether certain areas of the hear would or wouldn’t
benefit from surgery.
• Evaluate brain abnormalities; tumors, memory disorders, seizures
and other central nervous system disorders.
• To map normal human brain and heart function.

10. Medical Fields Of Application

11. PET Image Fusion Technique
•Fusion of a PET scan with MRI, CT or alternative image
to give functional and anatomical information.

12. CT scan

13. PET scan

14. Fused PET and CT image

16. Benefits And Risks Of PET
Benefits of PET:
•Image information unique- high sensitivity
•yields most useful information compared to other imaging techniques
from a pathological view.
•High spatial resolution
• more precise, cheaper, and more esthetical than exploratory surgery.
•Can detect a disease at an earlier stage than ex. CT scans or MRI.
•Result in low radiation exposure. (obs. not more than any other type of
imaging method!)
Risks with PET:
•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