Fast feldkamp reconstruction based on focus of attention and distributed computing

The Feldkamp algorithm is widely accepted as a practical conebeam reconstruction method for three-dimensional x-ray computed tomography. We introduce focus of attention, an effective and simple to implement datadriven preprocessing scheme, for identifying a convex subset of voxels that include all those relevant to the object under study. By concentrating on this subset of voxels during reconstruction, we reduce the computational demands of the Feldkamp algorithm correspondingly. To achieve further speed-up, all computations are distributed across a cluster of inexpensive, dual-processor PCs. We present experimental work based on mouse data obtained from the MicroCAT which is a high-resolution x-ray computed tomography system for small animal imaging. This work shows that focus of attention can cut the overall computation time in half without affecting the image quality. The method is general by nature and can easily be adapted to apply to other geometries and modalities as well as to iterative reconstruction algorithms.