Clinical time OSEM3D: infrastructure issues

In previous work we compared two parallel algorithms for calculating 3D forward and backprojection on a distributed-memory cluster computer. These two methods were used to develop an implementation of fully three-dimensional ordered subset expectation maximization iterative reconstruction for emission tomography (OSEM3D). It is, however, necessary to embed these computational kernels in an environment that supports efficient data movement and other infrastructural operations, such as process management. Here we briefly describe two particular components of the infrastructure: the I/O subsystem and the service demon. For the I/O subsystem, a fortuitous relationship between the traditional representation of the fully three-dimensional sinogram S_4DO(θ,z,φ,r) and the distributed representation for image space decomposition permits an efficient solution involving minimal data movement. The service demon is similar to others, but contains additional recovery-oriented mechanisms for minimizing mean time to repair. We conclude with performance benchmarks for fully 3D reconstruction for a scanner that produces a significant volume of data.