Document Detail


Iterative three-dimensional expectation maximization restoration of single photon emission computed tomography images: application in striatal imaging.
MedLine Citation:
PMID:  16485409     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Single photon emission computed tomography imaging suffers from poor spatial resolution and high statistical noise. Consequently, the contrast of small structures is reduced, the visual detection of defects is limited and precise quantification is difficult. To improve the contrast, it is possible to include the spatially variant point spread function of the detection system into the iterative reconstruction algorithm. This kind of method is well known to be effective, but time consuming. We have developed a faster method to account for the spatial resolution loss in three dimensions, based on a postreconstruction restoration method. The method uses two steps. First, a noncorrected iterative ordered subsets expectation maximization (OSEM) reconstruction is performed and, in the second step, a three-dimensional (3D) iterative maximum likelihood expectation maximization (ML-EM) a posteriori spatial restoration of the reconstructed volume is done. In this paper, we compare to the standard OSEM-3D method, in three studies (two in simulation and one from experimental data). In the two first studies, contrast, noise, and visual detection of defects are studied. In the third study, a quantitative analysis is performed from data obtained with an anthropomorphic striatal phantom filled with 123-I. From the simulations, we demonstrate that contrast as a function of noise and lesion detectability are very similar for both OSEM-3D and OSEM-R methods. In the experimental study, we obtained very similar values of activity-quantification ratios for different regions in the brain. The advantage of OSEM-R compared to OSEM-3D is a substantial gain of processing time. This gain depends on several factors. In a typical situation, for a 128 x 128 acquisition of 120 projections, OSEM-R is 13 or 25 times faster than OSEM-3D, depending on the calculation method used in the iterative restoration. In this paper, the OSEM-R method is tested with the approximation of depth independent resolution. For the striatum this approximation is appropriate, but for other clinical situations we will need to include a spatially varying response. Such a response is already included in OSEM-3D.
Authors:
Pierre Gantet; Pierre Payoux; Anna Celler; Cynthia Majorel; Daniel Gourion; Dominikus Noll; Jean-Paul Esquerré
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Publication Detail:
Type:  Evaluation Studies; Journal Article    
Journal Detail:
Title:  Medical physics     Volume:  33     ISSN:  0094-2405     ISO Abbreviation:  Med Phys     Publication Date:  2006 Jan 
Date Detail:
Created Date:  2006-02-20     Completed Date:  2006-03-14     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0425746     Medline TA:  Med Phys     Country:  United States    
Other Details:
Languages:  eng     Pagination:  52-60     Citation Subset:  IM    
Affiliation:
Laboratoire de Biophysique EA3033, Université Paul Sabatier Toulouse, France.
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MeSH Terms
Descriptor/Qualifier:
Algorithms*
Corpus Striatum / radionuclide imaging*
Humans
Image Enhancement / methods*
Image Interpretation, Computer-Assisted / methods*
Imaging, Three-Dimensional / methods*
Information Storage and Retrieval / methods
Likelihood Functions
Phantoms, Imaging
Reproducibility of Results
Sensitivity and Specificity
Tomography, Emission-Computed, Single-Photon / instrumentation,  methods*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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