The PET scan is a technique used in medicine mainly to detect tumors and which is increasingly widespread. It has many advantages, relating to the other techniques (NMR, CT...).
However, some events lead to a distorsion of the picture. We particularly stress the role played by fortuitous coincidences : bad lines of response will be detected because of therm so that in the end a false localization of the positron emitter will be suspected.
Professor Demortier found a way to decrease the number of false coincidences. We shall use the property of some isotopes to achieve stability by an emission of positrons and the emission of a gamma ray called "secondary gamma". The idea is to detect annihilation photons if a secondary gamma has been detected before. So, the probability of detecting a fortuitous coincidence is radically reduced. The best isotope for this new technique is the 94Tc.
The purpose of this thesis was to study the properties of scintillators (NaI) and semiconductor detectors (HPGe). Thanks to this study, we shall be able to use them in the best way to minimize the losses due to fortuitous coincidences. After this analyses, I shall give an example of the geometric configuration we have to achieve in order to utilize the new detector system. Moreover, a study will be carried out on two specific radioelements : the 93Tc and the 95Tc. With this analysis, we shall determine wether the 95Tc is a positron emitter, contrary to what we can read in the reference books used fot this thesis.
|Date of Award||2003|
|Supervisor||Guy Demortier (Supervisor)|