POSITRON EMISSION TOMOGRAPHY ( PET SCAN)

All you need to know about PET scan, it's applications, advantages and disadvantages, about Radiopharmaceutical and colour spectrum.

1. Pet scan POSITRON EMISSION TOMOGRAPHY by simran POSITRON EMISSION TOMOGRAPHY

2. INDEX 1. INTRODUCTION 2. ABOUT PET SCAN 3. PET SCANNER IMAGE 4. PET-CT AND PET-MRI IMAGES 5. HISTORY OF PET SCAN 6. VERY FIRST PET-LIKE IMAGINING 7. PET TRACER 8. HOW RADIOPHARMACEUTICAL IS 9. THE PROCESS OF PET TRACER 10. COLOUR SPECTRUM OF PET SCAN 11. APPLICATIONS OF PET SCAN 12. PATIENT PREPARATION FOR PET SCAN 13. ADVANTAGES OF PET SCAN 14. DISADVANTAGES OF PET SCAN

3. A positron emission tomography (PET) scan is an imaging test that can help reveal the metabolic or biochemical function of the body’s tissues and organs. INTRODUCTION

4. About PET SCAN ● It uses gamma rays to get image, not X-rays. ● The PET scan uses a radioactive drug called a tracer to show both typical and atypical metabolic activity. ● PET scan is used for oncology(cancer), neurology, cardiology ● PET scan doesn’t show organs shape, like CT and MRI. ● It shows how active organ is, what chemicals it is using ,how cells are functioning basically the metabolic and biochemical functions. ● In most hospitals, PET scan is combined with CT i.e PET- CT to show body structure and organs shape. ● In advance centres, PET- MRI is in use.

5. P PET-MRI PET-CT

6. 📜 History of PET Scan ● 1896 – Discovery of radioactivity by Henri Becquerel, which laid the foundation for nuclear medicine.
● 1930s–1940s – Development of cyclotrons (particle accelerators) by Ernest Lawrence, allowing production of short-lived positron-emitting isotopes.
● 1931–1934 – Carl Anderson discovered the positron (antimatter electron), key particle for PET technology.
● 1940s–1950s – First use of radioactive tracers in humans (like radioiodine) for studying metabolism and thyroid function. ● 1973 – First PET scanner developed by Michael Phelps, Edward Hoffman, and Michel Ter-Pogossian at Washington University in St. Louis.
● 1974–1976 – First human PET studies conducted using [18F]- fluorodeoxyglucose (FDG), the tracer still widely used today.
● 1980s – PET began being applied in neurology (brain metabolism, epilepsy, dementia) and oncology (cancer detection). ● 2000s – Introduction of PET/CT hybrid scanners, combining functional PET with anatomical CT images for more precise diagnosis.
● 2010s – Development of PET/MRI hybrid scanners, improving soft tissue contrast with functional imaging.

7. ● 1953 – Dr. Gordon Brownell and Dr. William Aronow at Massachusetts General Hospital (Boston) developed the first clinical positron imaging device.
● This was before today’s PET scanners existed.
● Their device used the principle of detecting gamma rays produced when positrons annihilate with electrons in the body. ●(A) Coincidence detection = the machine detected two gamma photons emitted simultaneously at 180° when a positron annihilates.
Darker region near the top of the head indicates increased tracer uptake.
This corresponds to recurrence of a brain tumor beneath the site of previous surgery. ● (B) cruder technique: detectors on opposite sides of the head compared radioactivity between left and right hemispheres.
Result shows asymmetry on the left side (dark patch).
It suggests higher activity ( tumor ) compared to the right side of the brain. Very first PET- like imagining

8. PET Traser ●A PET tracer is a radioactive compound used in Positron Emission Tomography (PET) to study body functions and detect diseases. ●It’s also called a radiopharmaceutical because it combines:
1) A radioactive isotope (for imaging)
Radionuclide (radioactive part): Emits positrons detected by the PET scanner.
Common examples: Fluorine-18 (¹⁸F), Carbon-11 (¹¹C), Oxygen-15 (¹⁵O), Nitrogen-13 (¹³N)
2) A biologically active molecule (to target a specific function or organ)
Pharmaceutical (carrier molecule): Determines where the tracer goes in the body.
Example: Glucose-like molecule in ¹⁸F-FDG targets tissues that use more glucose (like the brain or tumors ).

9. ● Different tracers are used for different purposes Tracer Radionuclide Used for ¹⁸F-FDG Fluorine-18 Glucose metabolism (cancer, brain, heart) ¹¹C-Methionine Carbon-11 Protein synthesis, brain tumors ¹³N-Ammonia Nitrogen-13 Myocardial perfusion (heart blood flow) ¹⁵O-Water Oxygen-15 Blood flow studies

10. How Radiodiopharmaceutical is ● Radioactive compound: it gives off radiation that scanner detects, ex. Fluorine-18 ● Linker: It is bridge that connect the radionuclide to the targeting molecule ● Targeting molecule: It is the biological active part of the tracer – it decides where tracer will go in body, it can be sugar, protein, peptide or antibody ● Target protein: It is where targeting molecule attaches to – a receptor on the cell surface ● Target cell: Final destination – A cell that’s the tracer binds to.

11. Process of PET tracer ● The tracer injected into IV in very tiny amount( 5-10 millicuries ), so it’s safe and doesn’t effect body. ● Then it travels through bloodstream to reach all parts of body and tracer goes to specific organs or cells that absorbs substance it made to imitate, like FDG acts like glucose so it goes to cells that use more sugar (usually cancer cells or brain cells ● The Target tissue ,like tumor , brain, heart, binds the tracer. More active or deceased cells take up more tracer, because they have higher metabolism. ● Then the radionuclide of tracer decays, means it is unstable so to be stable it releases energy, positron( which has + ve charge), the positron meets eletron then they destroy each other, the destroying is called Annihilation , this release two gamma rays and then the PET scanner detect gamma rays to make image. ● Then the computer turns the raw data into colourful 3D images that shows how organs and tissues are working.

12. Colour Metabolic Activity Red Very High Orange High Yellow Moderate to high Green Moderate Blue Low Black Very low or non Colour spectrum of PET scan

13. Applications of PET Scan Oncology: Detects, stages, and monitors cancer; checks treatment response; finds recurrence. Neurology: Studies brain function; helps diagnose Alzheimer’s, epilepsy, Parkinson’s, and brain tumors . Cardiology: : Evaluates heart blood flow, detects coronary artery disease, and identifies viable heart tissue. Infection & Inflammation: Locates hidden infections, fever of unknown origin, or inflammatory diseases.

14. Patient Preparation for pet scan Fasting: no food for 4-6 hours before scan, because eating increase blood suger and insulin, which can effect tracer distribution Avoid exercise for 24 hour before scan: exercise increases muscles metabolism, tracer will collects into muscles Check blood sugar level: should be below 150mg/dL. No talking or chewing during uptake time: It activates head and neck muscles – false tracer uptake Remove all the metal and jewellery

15. Advantages of PET scan ●Detects disease at a very early stage, even before structural changes are visible on CT/MRI.
‎●Shows metabolism and activity of tissues (not just structure).
‎●Useful for detecting spread (metastasis) of cancer in a single test.
‎●Treatment Monitoring → Helps to see if chemotherapy, radiotherapy, or surgery is working.
‎●Guides Biopsy/Surgery → Shows the most active part of a tumor to target for biopsy.
●‎Fused Imaging (PET/CT, PET/MRI) → Combines functional and anatomical details for better accuracy.
●‎Non-invasive and usually safe.
●‎PET traser does not cause any harm to patient organs in any conditions.

16. Disadvantages of PET scan ‎● Time- consuming .
‎● PET scans are very expensive form of imagining
‎● are not always readily available all the time.
‎● Radiation doses of patient is really high . ● PET scan alone doesn’t give details anatomy structure (need CT/MRI fusion for accuracy) ● Sometimes gives false positives and negatives. ● Pregnant or breastfeeding women are advice against it due to radiation ●Radioisotopes like FDG decay quickly, so scan must be scheduled in time and precisely.

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