Projector model for efficient list-mode reconstruction in PET scanners with parallel planar detectors

Abstract

Abstrcwt-We have developed a new projector model speciflcally tailored for fast list-mode tomographic reconstructions in Positrón emission tomography (PET) scanners with parallel planar detectors. The model provides an accurate estimation of the probability distribution of coincidence events defined by pairs of scintillating crystals. This distribution is parameterized with 2D elliptical Gaussian functions defined in planes perpendicular to the main axis of the tube of response (TOR). The parameters of these Gaussian functions have been obtained by fitting Monte Cario simulations that include positrón range, acolinearity of gamma rays, as well as detector attenuation and scatter effects. The proposed model has been applied efficiently to list-mode reconstruction algorithms. Evaluation with Monte Cario simulations over a rotating high resolution PET scanner indicates that this model allows to obtain better recovery to noise ratio in OSEM (ordered-subsets, expectationmaximization) reconstruction, if compared to list-mode reconstruction with symmetric circular Gaussian TOR model, and histogram-based OSEM with precalculated system matrix using Monte Cario simulated models and symmetries.

Projector with realistic detector scatter modelling for PET list-mode reconstruction

“…Projector modeling 1) Shift varying Gaussian PSF modeling: One of the most commonly used projector model is based on approximating the VOR as a spatially varying Gaussian point spread func tion (PSF). Some assume the PSF is a symmetric invariant Gaussian function [2]. A more accurate 2D asymmetrical Gaussian function [3] was used as PSF model in this study.…”

“…The model is composed of a decreasing exponential function along the crystal depth direction with Aout as decreasing factor and, in the orthogonal plan, a decreasing exponential function with a factor A�out and a circular symmetry with Osym as varying center of symmetry. Then, we propose an empirical model for the five parameters a3 cos (a) A�out = Constant Osym = a4 sin (a) (2) Where aI, bl, a2, a3, Constant and a4 are the parameters of this model. It has the advantage of fully model the detector and varies depending on the incidence of the LOR in the crystal.…”

“…The VOR has a complex shape varying according to the LOR and its position in the field-of-view (FOV), and also depends on physical effects such as detector scatter. Recently proposed projectors use Gaussian function as model of the LOR-PDF [2], [3]. However, a Gaussian model is an approximation of VOR shape.…”

Performance evaluation of a 90°-rotating dual-head small animal PET system

“…Some SRM estimation geometrical methods are geometrical methods (Herman andMeyer 1993, Zhuang et al 1994), point spread functional fitting methods (Panin et al 2006a(Panin et al , 2006b or Monte Carlo Methods (Rafecas et al 2004, Shokouhi et al 2004, Buvat and Lazaro 2006, Kao et al 2007b, Ortuno et al 2010, Ortuño et al 2011, Liu et al 2013. The Monte Carlo method was employed in order to obtain the highest SRM accuracy and dual functions as both computer simulation of PET as well as the actual PET system.…”

Development and evaluation of a small animal PET protype compatible with strong magnetic fields

“…However, researchers over the past ten years have proposed several methods to reconstruct on-the-fly listmode data, without sorting the data to sinograms [61,62].…”