PET Imaging and Time of Flight (ToF)

The principle is that the patient is injected with a PET tracer (a radioactive tracer with a short half-life, bound, for example, to sugar) and then imaged as follows: as the isotopes in the radioactive substance decay, they send out positrons (i.e. elementary particles with the opposite charge to electrons). After a few millimetres each of the positrons collide with an electron and this process produces gamma rays that travel along a line in opposite directions. These gamma rays are registered by a detector ring. Only the photons that come in pairs simultaneously are of interest as then one knows that an event (the decay of a radioactive isotope) has occurred somewhere along the line, that is, one looks at the event as occurring at a point that is equally valid along the entire line. This means that PET images, despite being able to capture processes down to the molecular level, are very blurry and have a low signal to noise ratio.

In this project we want to investigate the possibility to use information about the "time of flight", i.e. how long the gamma rays (in the same pair) have used to reach the detector. If one could use this extra information, then it would be possible to localise an event to a smaller segment of the line, and this could be used to create better images, with less uncertainty in the signal. This technique is not very common yet. See more here:

http://www.uphs.upenn.edu/news/News_Releases/jun06/PETCTITC.html 

The project is very relevant, especially in connection with the PET focus in Bergen. It is envisaged that this project would be carried out parallel to a master's or PhD in Physics and Technology (UiB), where a prototype of a PET machine with ToF is being constructed.

If you are interested, please contact Antonella Z. Munthe-Kaas (Matematisk institutt, UiB), Renate Grüner (Fysikk og Teknologi, UiB), or Yngve Kvinnesland (Nordic Neuro Lab).