Enhanced 3D PET OSEM reconstruction using inter-update Metz filtering^*

Abstract

We present an enhancement of the OSEM (ordered set expectation maximization) algorithm for 3D PET reconstruction, which we call the inter-update Metz filtered OSEM (IMF-OSEM). The IMF-OSEM algorithm incorporates filtering action into the image updating process in order to improve the quality of the reconstruction. With this technique, the multiplicative correction image--ordinarily used to update image estimates in plain OSEM--is applied to a Metz-filtered version of the image estimate at certain intervals. In addition, we present a software implementation that employs several high-speed features to accelerate reconstruction. These features include, firstly, forward and back projection functions which make full use of symmetry as well as a fast incremental computation technique. Secondly, the software has the capability of running in parallel mode on several processors. The parallelization approach employed yields a significant speed-up, which is nearly independent of the amount of data. Together, these features lead to reasonable reconstruction times even when using large image arrays and non-axially compressed projection data. The performance of IMF-OSEM was tested on phantom data acquired on the GE Advance scanner. Our results demonstrate that an appropriate choice of Metz filter parameters can improve the contrast-noise balance of certain regions of interest relative to both plain and post-filtered OSEM, and to the GE commercial reprojection algorithm software.

A unified noise analysis for iterative image estimation

“…The noise analysis can also be extended to the algorithms with inter-update linear filtering [Silverman et al, 1990, Jacobson et al, 2000. Inter-update filtering was introduced to reduce the noise in the ML-EM algorithm.…”

3D tomographic imaging with the γ-eye planar scintigraphic gamma camera

“…The OSMAPOSL algorithm is a refined OSEM style algorithm that can optionally include prior terms [10]. Where the use of prior terms has been explored, the quadratic Gibbs prior was used with value p controlling the weight of the prior term.…”

Geoscientific process monitoring with positron emission tomography (GeoPET)

“…The OSEM reconstruction algorithm (Jacobson et al, 2000) implemented in STIR is an iterative procedure (iteration step j ) for computing the activity a in one voxel v from the count number n in a set of bins b described by…”