Positron range effects in high resolution 3D PET imaging

Proceeding of: 2009 IEEE Nuclear Science Symposium Conference Record (NSS/MIC), Orlando, Florida, 25-31 October 2009 Positron range limits the spatial resolution of PET images. It has a different effect for different isotopes and propagation materials, therefore it is important to consider it during image reconstruction, in order to obtain the best image quality. Positron range distribution was computed using Monte Carlo simulations with PeneloPET. The simulation models positron trajectories and computes the spatial distribution of the annihilation coordinates for the most common isotopes used in PET: 18F, 11C, 13N, 15O, 68Ga and 82Rb. Range profiles are computed for different positron propagation materials, obtaining one kernel profile for each isotope-material combination. These range kernels were introduced in FIRST, a 3D-OSEM image reconstruction software, and employed to blur the object during forward projection. The blurring introduced takes into account the material in which the positron is annihilated, obtained for instance from a CT image. In this way, different positron range corrections for each material in the phantom are considered. We compare resolution and noise properties of the images reconstructed with and without positron range modelling. For this purpose, acquisitions of an Image Quality phantom filled with different isotopes have been simulated for the ARGUS small animal PET scanner. This work has been supported in part by MEC (FPA2007 62216), CDTEAM (Programa CENIT, Ministerio de Industria), UCM (Grupos UCM, 910059), CPAN (Consolider Ingenio 2010) CSPD 2007 00042 and the RECAVA RETIC network. Part of the calculations of this work were performed in the “Clúster de Cálculo de Alta Capacidad para Técnicas Físicas” funded in part by UCM and in part by UE under FEDER programme”.