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Multi-ray-based system matrix generation for 3D PET reconstruction

Tijdschriftbijdrage - Tijdschriftartikel

Iterative image reconstruction algorithms for positron emission tomography
(PET) require a sophisticated system matrix (model) of the scanner. Our aim
is to set up such a model offline for the YAP-(S)PET II small animal imaging
tomograph in order to use it subsequently with standard ML-EM and OSEM
for fully three-dimensional image reconstruction. In general, the system model
can be obtained analytically, via measurements or via Monte Carlo simulations.
In this paper, we present the multi-ray method, which can be considered as
a hybrid method to set up the system model offline. It incorporates accurate
analytical (geometric) considerations as well as crystal depth and crystal scatter
effects. At the same time, it has the potential tomodel seamlessly other physical
aspects such as the positron range. The proposed method is based on multiple
rays which are traced from/to the detector crystals through the image volume.
Such a ray-tracing approach itself is not new; however, we derive a novel
mathematical formulation of the approach and investigate the positioning of
the integration (ray-end) points. First, we study single system matrix entries
and show that the positioning and weighting of the ray-end points according to
Gaussian integration give better results compared to equally spaced integration
points (trapezoidal integration), especially if only a small number of integration
points (rays) are used. Additionally, we show that, for a given variance of the
singlematrix entries, the number of rays (events) required to calculate the whole
matrix is a factor of 20 larger when using a pure Monte-Carlo-based method.
Finally, we analyse the quality of the model by reconstructing phantom data
from the YAP-(S)PET II scanner.
Tijdschrift: Phys. Med. Biol.
ISSN: 0031-9155
Volume: 53
Pagina's: 6925-6945
Jaar van publicatie:2008
Trefwoorden:tomography, image reconstruction
  • Scopus Id: 58149269274