Flashcards in Imaging In Inflammatory Disorders and Infection Deck (21):
What is a PET used to view?
Metabolic processes in the body
What is another name given to the tracer that is introduced into the body on a biologically active molecule?
A positron-emitting radionuclide
How is the 3-D image created?
Detected gamma rays are used to determine tracer concentration within the body, this is then used in computer analysis to construct the 3D image.
Why is the biological molecule used in a PET scan an analogue of glucose, for example fludeoxyglucose?
The concentrations of tracer will indicate the metabolic activity as it will correspond to the regional glucose uptake
What is the most common use of the PET scan?
To explore the possibility of cancer metastasis
What can PET also be used for?
Clinical diagnosis of certain diffuse brain diseases such as those causing various types of dementia.
Important research tool to find map out the normal human brain and heart function.
What is the best detector for PET imaging?
PET scanner, however dual headed conventional gamma camera can be used, quality of image is however much lower
Why does a patient have to wait after ingesting the radioactive tracer or isotope?
To allow time for the active molecule to become concentrated in the tissue of interest.
What does the radioisotope in a PET scan emit?
A positron, antiparticle of electron with opposite charge
What happens to the emitted positrons?
They decelerate until they are able to interact with electrons, at this encounter both the electron and the positron are annihilated producing a pair annihilation photons moving in approximately opposite directions. These are detected in the scanning device.
How do gamma rays occur?
The radioactive decay of unstable isotopes
What are the properties of an ideal isotope used in radiography?
Half-life similar to length of examination.
Energy of rays between 50-300 keV
Radionuclide should be readily available at hospital site
Easily bound to pharmaceutical component
Radiopharmecutical should be easy to prepare
What type of radiation does a radionuclide emit?
What makes the picture in a PET scan?
Gamma rays are created during the emission of positrons and the scanner then detects the gamma rays. An image of the map or organ is then created by computer analysis of the data collected by the scanner.
What is often combined with PET? And Why?
CT scans, provides a more definitive information about malignant tumours and other lesions
What does SPECT stand for?
Single photon emission computed tomography.
What is the difference between PET scans and SPECT?
The type of radio tracers used, SPECT radioisotopes emit gamma radiation.
What is the estimated effective radiation of a PET scan?
What is the effective dose or a radiography chest?
What is the effective dose of CT chest?