EM-ML PET RECONSTRUCTION ON MULTIPLE PROCESSORS WITH REDUCED COMMUNICATIONS

Positron emission tomography (PET) reconstruction by the EM algorithm is an iterative computation of Poisson emission rates to maximize a li kelihood function. The method is time consuming and, for real scanner data, requires large numerical arrays. To speed up the computation on multiple processors which have their own local memory and communicate by passing messages on a network, a parallel method has been implement ed in which processors compute several iterations before exchanging th eir latest data with other processors. This method is convenient for i terative reconstruction using a relatively small number of interconnec ted, standard processors such as workstations on a local-area network. Computational aspects of the method are explained and illustrated wit h two-dimensional reconstructions from a simulation and from sinograms produced by a PET scanner. Five hundred twelve (512) iterations are c omputed on a local-area network of workstations and, for reference, on a distributed-memory multiprocessor computer. The method is capable o f producing high-quality reconstructions with significant speed-up. (C ) 1996 John Wiley & Sons, Inc.