A PET scan (Positron Emission Tomography scan) is a medical imaging test that helps doctors see how tissues and organs are functioning inside the body.
How it works?
A small amount of a radioactive tracer is injected into a vein (sometimes swallowed or inhaled).
The tracer travels through the body and collects in areas with high metabolic activity.
A PET scanner detects the radiation emitted by the tracer and creates detailed images.
What is it used for?
PET scans are commonly used to:
Detect and monitor cancer
Evaluate heart disease
Assess brain disorders such as Alzheimer’s disease, epilepsy, or certain tumors
Check how well a treatment is working
What happens during the test?
You receive the tracer and wait about 30–60 minutes for it to distribute through your body.
You lie on a table that moves through the PET scanner.
The scan itself usually takes 20–45 minutes.
The procedure is generally painless.
Is it safe?
The amount of radiation used is small and usually considered safe. However, you should tell your doctor if you are:
Pregnant or think you might be pregnant
Breastfeeding
Allergic to any medications or contrast materials
A PET scan is often combined with a CT scan or MRI to provide both functional and anatomical information, helping doctors make more accurate diagnoses.
What is PET scan ?
A PET scan is a nuclear medicine imaging technique that provides functional information about organs and tissues. Unlike X-rays, CT, or MRI, which mainly show anatomy, PET shows how cells are working and using energy.
Basic Principle
PE imaging is based on the detection of positrons emitted by a radioactive tracer.
A radioactive tracer (usually Fluorodeoxyglucose (FDG)) is injected into the patient.
FDG behaves like glucose and is taken up by body cells.
Active cells (such as cancer cells) consume more glucose and absorb more FDG.
The tracer emits positrons.
When a positron meets an electron, they annihilate each other and produce two gamma rays traveling in opposite directions.
The PET scanner detects these gamma rays and creates an image showing metabolic activity.
Main Components of a PET Scanner:
Gantry – Circular structure containing detectors
Scintillation Crystals – Convert gamma rays into light
Photodetectors – Convert light into electrical signals
Computer System – Reconstructs images
Patient Table – Moves the patient through the scanner
Common Radiotracers
Radiotracer
Use:
FDG (18F-FDG)
Cancer, brain, heart studies
18F-NaF
Bone imaging
13N-Ammonia
Cardiac perfusion
11C & 18F compounds
Brain research
Advantages
✅ Detects disease at an early stage
✅ Provides functional information
✅ High sensitivity for cancer detection
✅ Helps assess treatment effectiveness
✅ Whole-body imaging possible
Disadvantages
❌ Expensive
❌ Involves radiation exposure
❌ Limited availability
❌ False-positive results can occur in infections or inflammation.
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