Lecture PET
7 important questions on Lecture PET
When is a positron created?
Which three types of events are there in PET?
- true coincidence: both gamma rays escape without scatter and interact in detectors.
- scatter coincidence: one or both gamma rays scatter in tissue.
- random coincidence: two gamma rays from seperate emissions strike the detecotrs at the same time.
Wherefore is pre-processing required in PET?
- to correct for random coincidences
- estimation and substraction of scattered photons.
- detector dead-time correction
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Which factors determine the spatial resolution in PET?
- The rms distance (root mean square distance) travelled by the positrons after being emitted by a isotope and before annihilation (sending out gamma rays).
- The residual energy of the electron-positron pair.
What is time of flight PET?
What is a cyclotron?
Electrons are "stripped" of protons, proton shoots out of the circle and is trapped into a molecule.
This process has to happen shorter than half life
When would you consider PET over MRI?
- ROI is inferior temporal lobe
- When you're interested in something with a low concentration; with PET you can measure strong signals from substances with low concentrations.
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