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Range Condition and ML-EM Checkerboard Artifacts.
- Source :
-
IEEE Transactions on Nuclear Science . Oct2007 Part 1 of 2, Vol. 54 Issue 5, p1696-1702. 7p. - Publication Year :
- 2007
-
Abstract
- The expectation maximization (EM) algorithm for the maximum likelihood (ML) image reconstruction criterion generates severe checkerboard artifacts in the presence of noise. A classical remedy is to impose an a priori constraint for a penalized ML or maximum a posteriori probability solution. The penalty reduces the checkerboard artifacts and also introduces uncertainty because a priori information is usually unknown in clinic. Recent theoretical investigation reveals that the noise can be divided into two components: one is called null-space noise and the other is range-space noise. The null-space noise can be numerically estimated using filtered backprojection (FBP) algorithm. By the FBP algorithm, the null-space noise annihilates in the reconstruction while the range-space noise propagates into the reconstructed image. The aim of this work is to investigate the relation between the null-space noise and the checkerboard artifacts in the ML-EM reconstruction from noisy projection data. Our study suggests that removing the null-space noise from the projection data could improve the signal-to-noise ratio of the projection data and, therefore, reduce the checkerboard artifacts in the ML-EM reconstructed images. This study reveals an in-depth understanding of the different noise propagations in analytical and iterative image reconstructions, which may be useful to single photon emission computed tomography, where the noise has been a major factor for image degradation. The reduction of the ML-EM checkerboard artifacts by removing the null-space noise avoids the uncertainty of using a priori penalty. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00189499
- Volume :
- 54
- Issue :
- 5
- Database :
- Academic Search Index
- Journal :
- IEEE Transactions on Nuclear Science
- Publication Type :
- Academic Journal
- Accession number :
- 27344437
- Full Text :
- https://doi.org/10.1109/TNS.2007.901198