1. A method for processing data associated with a nuclear medical imaging technique, comprising the steps of: ordering, with a computer processor, a plurality of data elements into a plurality of ordered data groups according to a spatial index order, wherein each of the plurality of ordered data groups has a plurality of data elements each with common first and second index values and a divergent third index value and the plurality of data elements are list mode events; fetching an ordered data group of the plurality of ordered data groups into a memory device; and processing each data element of the ordered data group from the memory device in the spatial index order, wherein the processing is part of a list mode based reconstruction.