How does positron emission tomography work physics?

How does PET work? 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.

What is the physics of a PET scan?

In most PET scanners today, scintillation detectors are used as detection elements. They couple inorganic scintillation crystals that emit visible or near ultraviolet light after interaction with an incident high-energy (511 keV) photon, to photo detectors that detect and measure the scintillation photons.

What is the principle of PET positron emission tomography scan?

The principle of positron emission tomography (PET) is that radiation emitted from a radiopharmaceutical injected intravenously into a patient is registered by external detectors positioned at different orientations.

How does a PET scanner work a level physics?

In PET scanning: Positrons are emitted by the decay of the tracer. They travel a small distance and annihilate when they interact with electrons in the tissue. This annihilation produces a pair of gamma-ray photons which travel in opposite directions.

How are PET images formed?

A radiopharmaceutical — a radioisotope attached to a drug — is injected into the body as a tracer. Gamma rays are emitted and detected by gamma cameras to form a three-dimensional image, in a similar way that an X-ray image is captured. PET scanners can incorporate a CT scanner and are known as PET-CT scanners.

Why does PET have low spatial resolution?

In order to reduce the number of electronics channels, most PET cameras have detectors that employ some form of optical multiplexing, where there are more scintillation crystals than photodetector elements. This decoding is often imperfect, which degrades the spatial resolution.

How are gamma rays produced in a PET scanner?

In PET the gamma rays used for imaging are produced when a positron meets an electron inside the patient’s body, an encounter that annihilates both electron and positron and produces two gamma rays travelling in opposite directions.

What chemical is used in PET scan?

The radioactive substance most commonly used in PET scanning is a simple sugar (like glucose) called FDG, which stands for “fluorodeoxyglucose”. It is injected into the bloodstream and accumulates in the body where it gives off energy in the form of gamma rays.

What is PET technique?

Positron emission tomography (PET) is a technique that measures physiological function by looking at blood flow, metabolism, neurotransmitters, and radiolabelled drugs.

What tracer is used in PET scan?

Before your PET-CT, you’ll get a radioactive medication with glucose called a tracer through an intravenous (IV) line in your arm. This is done to show differences between healthy tissue and diseased tissue. Your PET-CT will use FDG as the tracer. FDG is taken up by your cells and doesn’t stay in your body long.

What are the main factors affecting the resolution of PET images?

The major factors that can affect the spatial resolution of PET images include size of the detector used; colinearity, or most precisely, noncolinearity of annihilating photons; and range of emitted positrons.

What determines PET resolution?

The physical size of the detector element usually plays the dominant role in determining resolution, but the combined contributions from acollinearity, positron range, penetration into the detector ring, and decoding errors in the detector modules often combine to be of similar size.

What type of radiation is used in PET scans?

What radioactive element is used in PET scans?

Oxygen-15 or 15O is an isotope of oxygen having a half life of about two minutes. The most commonly used isotope in PET scans is fluorine-18. It is a fluorine isotope with a half life of approximately 110 minutes.

Why is fluorine-18 used in PET scans?

Fluorine-18 is one of the several isotopes of fluorine that is routinely used in radiolabeling of biomolecules for PET; because of its positron emitting property and favorable half-life of 109.8 min.

How are radioactive particles produced in PET scans?

The PET Scan Process As the isotope used in the radiolabeled oxygen or glucose undergoes radioactive decay, it emits high energy positions (anti-matter) which collide with electrons resulting in bursts of γ-radiation.

How is PET signal generated?

The PET Scanning Process As the patient slides through the circular opening of the scanner, the tracer emits radioactive signals. These signals are recorded by multiple rings of detectors in the scanner and are converted into three-dimensional computer images of tissue concentrations and organ function.

Does PET scan use gamma rays?

PET scans register the gamma rays emitted from positron-electron annihilation. These positrons are given off by a radioactive isotope during positron decay. The scan process starts with the patient being injected with some type of radioactive tracer that has been attached to some metabolized molecule, such as glucose.

What is PET sensitivity?

Sensitivity for different sources The sensitivity of a PET scanner is defined as the number of 511-keV photon pairs per unit time detected by the device for each unit of activity present in a source. It is normally expressed in counts per second per microcurie (or megabecquerel) (cps/microCi or cps/kBq).

What are the fundamental limiting factors for PET image resolution?

The “fundamental” effects that limit the spatial resolution in PET cameras are the detector width, the positron range, and the acollinearity.

What happens during positron emission?

– Thermionic Emission. – Photoelectric Emission. – Secondary Emission. – Field Emission.

What does positron emission mean?

Positron emission, beta plus decay, or β + decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (ν e). Positron emission is mediated by the weak force.The positron is a type of beta particle (β +), the other beta particle being the electron (β −) emitted

How long does it take to get results from a PET scan?

How soon will the PET scan results be available? A radiologist who has specialized training in PET scans will interpret the images, write a report, and deliver the results to your doctor. This process usually takes 24 hours.

Why is my doctor recommending a PET scan?

– Lung cancer – Lymphoma – Colorectal cancer – Melanoma – Head and neck cancer – Breast cancer