1. A method for estimating the line of response for a coincident detection in a positron emission tomography scanner comprising the steps: (a) identifying a coincident event in a positron emission tomography scanner wherein a first detector module detects at least one photon-producing interaction and a second detector module disposed opposite the first detector module detects a plurality of photon-producing interactions, and wherein all of said photon-producing interactions in both the first and second detector modules occur close enough in time to be coincident for purposes of positron emission tomography; (b) selecting one of the at least one photon-producing interactions in the first detector module, and selecting one of the plurality of photon-producing interactions in the second detector module; (c) calculating the joint probability that the selected photon-producing interaction in the first detector module and the selected photon-producing interactions in the second detector module are the first occurring photon-producing interactions in both detector modules for the identified coincident event; (d) repeating steps (b) and (c) for all permutations of photon-producing interactions in the first detector module and photon-producing interactions in the second detector module; (e) using the permutation having the largest calculated joint probability to construct an estimated line of response.