Principe et technique de la tomographie par émission de positons (TEP)

Abstract

Positron Emission Tomography (PET) is a medical imaging modality, which provides the in-vivo distribution of a compound labeled by a positron emitter. The acquisition is peformed by a set of detector fitted on a ring. The detector is based on a scintillator chosen in order to optimize the efficiency and the signal to noise ratio. Coincidence detection is dedicated to measure the two 511 keV photons resulting from the annihilation of the positron. Tomographic slices are reconstructed thanks to sophisticated algorithms adapted to the tri dimension acquisitions. The quantification of PET images is achieved by the correction of the main physical effects that alter the detection process. For the patient, the effectives doses resulting for a PET examination is about 8 mSv. The installation of a PET device requires specific investments to ensure the radioprotection of the staff. The PET evolution is very fast, this is particularly important for the detectors and for the algorithms. Recently, a new generation of PET/CT devices has been developed to benefit of the complimentarity of both modalities. The CT images can be used for attenuation correction, to localize the lesion detected by PET and to optimize the therapeutical procedures. Thanks to all these developments, PET is a powerful diagnostic tool among the other medical imaging modalities.