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OSEM (ordered subset EM)
ESTRO Teaching Course Advanced Imaging: PET – Reconstruction, Contouring
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Accelerated version of ML-EM
LOR data are partitioned in
S
disjoint subsets
Commonly, projections are divided into subsets with
different views, or azimuthal angles
ML-EM algorithm for data from one subset only
Each subset processed in well-defined order
Convergence accelerated by factor ≈
S
LOR
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