Development of Regularized Expectation Maximization Algorithms for Fan-Beam SPECT Data.
- Author:
Soo Mee KIM
1
;
Jae Sung LEE
;
Soo Jin LEE
;
Kyeong Min KIM
;
Dong Soo LEE
Author Information
1. Department of Nuclear Medicine and Interdisciplinary Program in Radiation Applied Life Science Major, Seoul National University College of Medicine, Seoul, Korea. jaes@snu.ac.kr
- Publication Type:Original Article
- Keywords:
Reconstruction;
Fan-beam projection data;
FBP;
EM;
OSL;
Ray-tracing method
- MeSH:
Brain;
Membranes;
Noise;
Tomography, Emission-Computed, Single-Photon*
- From:Korean Journal of Nuclear Medicine
2005;39(6):464-472
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
PURPOSE: SPECT using a fan-beam collimator improves spatial resolution and sensitivity. For the reconstruction from fan-beam projections, it is necessary to implement direct fan-beam reconstruction methods without transforming the data into the parallel geometry. In this study, various fan-beam reconstruction algorithms were implemented and their performances were compared. MATERIALS AND METHODS: The projector for fan-beam SPECT was implemented using a ray-tracing method. The direct reconstruction algorithms implemented for fan-beam projection data were FBP (filtered backprojection), EM (expectation maximization), OS-EM (ordered subsets EM) and MAP-EM OSL (maximum a posteriori EM using the one-step late method) with membrane and thin-plate models as priors. For comparison, the fan-beam projection data were also rebinned into the parallel data using various interpolation methods, such as the nearest neighbor, bilinear and bicubic interpolations, and reconstructed using the conventional EM algorithm for parallel data. Noiseless and noisy projection data from the digital Hoffman brain and Shepp/Logan phantoms were reconstructed using the above algorithms. The reconstructed images were compared in terms of a percent error metric. RESULTS: For the fan-beam data with Poisson noise, the MAP-EM OSL algorithm with the thin-plate prior showed the best result in both percent error and stability. Bilinear interpolation was the most effective method for rebinning from the fan-beam to parallel geometry when the accuracy and computation load were considered. Direct fan-beam EM reconstructions were more accurate than the standard EM reconstructions obtained from rebinned parallel data. CONCLUSION: Direct fan-beam reconstruction algorithms were implemented, which provided significantly improved reconstructions.
